natural selection research paper ideas

Volume 2 Supplement 2

Special Issue: Transitional Fossils

• Evolutionary Concepts
• Open access
• Published: 09 April 2009

Understanding Natural Selection: Essential Concepts and Common Misconceptions

• T. Ryan Gregory 1  

Evolution: Education and Outreach volume  2 ,  pages 156–175 ( 2009 ) Cite this article

379k Accesses

135 Citations

374 Altmetric

Metrics details

Natural selection is one of the central mechanisms of evolutionary change and is the process responsible for the evolution of adaptive features. Without a working knowledge of natural selection, it is impossible to understand how or why living things have come to exhibit their diversity and complexity. An understanding of natural selection also is becoming increasingly relevant in practical contexts, including medicine, agriculture, and resource management. Unfortunately, studies indicate that natural selection is generally very poorly understood, even among many individuals with postsecondary biological education. This paper provides an overview of the basic process of natural selection, discusses the extent and possible causes of misunderstandings of the process, and presents a review of the most common misconceptions that must be corrected before a functional understanding of natural selection and adaptive evolution can be achieved.

“There is probably no more original, more complex, and bolder concept in the history of ideas than Darwin's mechanistic explanation of adaptation.” Ernst Mayr ( 1982 , p.481)

Introduction

Natural selection is a non-random difference in reproductive output among replicating entities, often due indirectly to differences in survival in a particular environment, leading to an increase in the proportion of beneficial, heritable characteristics within a population from one generation to the next. That this process can be encapsulated within a single (admittedly lengthy) sentence should not diminish the appreciation of its profundity and power. It is one of the core mechanisms of evolutionary change and is the main process responsible for the complexity and adaptive intricacy of the living world. According to philosopher Daniel Dennett ( 1995 ), this qualifies evolution by natural selection as “the single best idea anyone has ever had.”

Natural selection results from the confluence of a small number of basic conditions of ecology and heredity. Often, the circumstances in which those conditions apply are of direct significance to human health and well-being, as in the evolution of antibiotic and pesticide resistance or in the impacts of intense predation by humans (e.g., Palumbi 2001 ; Jørgensen et al. 2007 ; Darimont et al. 2009 ). Understanding this process is therefore of considerable importance in both academic and pragmatic terms. Unfortunately, a growing list of studies indicates that natural selection is, in general, very poorly understood—not only by young students and members of the public but even among those who have had postsecondary instruction in biology.

As is true with many other issues, a lack of understanding of natural selection does not necessarily correlate with a lack of confidence about one's level of comprehension. This could be due in part to the perception, unfortunately reinforced by many biologists, that natural selection is so logically compelling that its implications become self-evident once the basic principles have been conveyed. Thus, many professional biologists may agree that “[evolution] shows how everything from frogs to fleas got here via a few easily grasped biological processes ” (Coyne 2006 ; emphasis added). The unfortunate reality, as noted nearly 20 years ago by Bishop and Anderson ( 1990 ), is that “the concepts of evolution by natural selection are far more difficult for students to grasp than most biologists imagine.” Despite common assumptions to the contrary by both students and instructors, it is evident that misconceptions about natural selection are the rule, whereas a working understanding is the rare exception.

The goal of this paper is to enhance (or, as the case may be, confirm) readers' basic understanding of natural selection. This first involves providing an overview of the basis and (one of the) general outcomes of natural selection as they are understood by evolutionary biologists Footnote 1 . This is followed by a brief discussion of the extent and possible causes of difficulties in fully grasping the concept and consequences of natural selection. Finally, a review of the most widespread misconceptions about natural selection is provided. It must be noted that specific instructional tools capable of creating deeper understanding among students generally have remained elusive, and no new suggestions along these lines are presented here. Rather, this article is aimed at readers who wish to confront and correct any misconceptions that they may harbor and/or to better recognize those held by most students and other non-specialists.

The Basis and Basics of Natural Selection

Though rudimentary forms of the idea had been presented earlier (e.g., Darwin and Wallace 1858 and several others before them), it was in On the Origin of Species by Means of Natural Selection that Darwin ( 1859 ) provided the first detailed exposition of the process and implications of natural selection Footnote 2 . According to Mayr ( 1982 , 2001 ), Darwin's extensive discussion of natural selection can be distilled to five “facts” (i.e., direct observations) and three associated inferences. These are depicted in Fig.  1 .

The basis of natural selection as presented by Darwin ( 1859 ), based on the summary by Mayr ( 1982 )

Some components of the process, most notably the sources of variation and the mechanisms of inheritance, were, due to the limited available information in Darwin's time, either vague or incorrect in his original formulation. Since then, each of the core aspects of the mechanism has been elucidated and well documented, making the modern theory Footnote 3 of natural selection far more detailed and vigorously supported than when first proposed 150 years ago. This updated understanding of natural selection consists of the elements outlined in the following sections.

Overproduction, Limited Population Growth, and the “Struggle for Existence”

A key observation underlying natural selection is that, in principle, populations have the capacity to increase in numbers exponentially (or “geometrically”). This is a simple function of mathematics: If one organism produces two offspring, and each of them produces two offspring, and so on, then the total number grows at an increasingly rapid rate (1 → 2 → 4 → 8 → 16 → 32 → 64... to 2 n after n rounds of reproduction).

The enormity of this potential for exponential growth is difficult to fathom. For example, consider that beginning with a single Escherichia coli bacterium, and assuming that cell division occurs every 30 minutes, it would take less than a week for the descendants of this one cell to exceed the mass of the Earth. Of course, exponential population expansion is not limited to bacteria. As Nobel laureate Jacques Monod once quipped, “What is true for E. coli is also true for the elephant,” and indeed, Darwin ( 1859 ) himself used elephants as an illustration of the principle of rapid population growth, calculating that the number of descendants of a single pair would swell to more than 19,000,000 in only 750 years Footnote 4 . Keown ( 1988 ) cites the example of oysters, which may produce as many as 114,000,000 eggs in a single spawn. If all these eggs grew into oysters and produced this many eggs of their own that, in turn, survived to reproduce, then within five generations there would be more oysters than the number of electrons in the known universe.

Clearly, the world is not overrun with bacteria, elephants, or oysters. Though these and all other species engage in massive overproduction (or “superfecundity”) and therefore could in principle expand exponentially, in practice they do not Footnote 5 . The reason is simple: Most offspring that are produced do not survive to produce offspring of their own. In fact, most population sizes tend to remain relatively stable over the long term. This necessarily means that, on average, each pair of oysters produces only two offspring that go on to reproduce successfully—and that 113,999,998 eggs per female per spawn do not survive (see also Ridley 2004 ). Many young oysters will be eaten by predators, others will starve, and still others will succumb to infection. As Darwin ( 1859 ) realized, this massive discrepancy between the number of offspring produced and the number that can be sustained by available resources creates a “struggle for existence” in which often only a tiny fraction of individuals will succeed. As he noted, this can be conceived as a struggle not only against other organisms (especially members of the same species, whose ecological requirements are very similar) but also in a more abstract sense between organisms and their physical environments.

Variation and Inheritance

Variation among individuals is a fundamental requirement for evolutionary change. Given that it was both critical to his theory of natural selection and directly counter to much contemporary thinking, it should not be surprising that Darwin ( 1859 ) expended considerable effort in attempting to establish that variation is, in fact, ubiquitous. He also emphasized the fact that some organisms—namely relatives, especially parents and their offspring—are more similar to each other than to unrelated members of the population. This, too, he realized is critical for natural selection to operate. As Darwin ( 1859 ) put it, “Any variation which is not inherited is unimportant for us.” However, he could not explain either why variation existed or how specific characteristics were passed from parent to offspring, and therefore was forced to treat both the source of variation and the mechanism of inheritance as a “black box.”

The workings of genetics are no longer opaque. Today, it is well understood that inheritance operates through the replication of DNA sequences and that errors in this process (mutations) and the reshuffling of existing variants (recombination) represent the sources of new variation. In particular, mutations are known to be random (or less confusingly, “undirected”) with respect to any effects that they may have. Any given mutation is merely a chance error in the genetic system, and as such, its likelihood of occurrence is not influenced by whether it will turn out to be detrimental, beneficial, or (most commonly) neutral.

As Darwin anticipated, extensive variation among individuals has now been well established to exist at the physical, physiological, and behavioral levels. Thanks to the rise of molecular biology and, more recently, of genomics, it also has been possible to document variation at the level of proteins, genes, and even individual DNA nucleotides in humans and many other species.

Non-random Differences in Survival and Reproduction

Darwin saw that overproduction and limited resources create a struggle for existence in which some organisms will succeed and most will not. He also recognized that organisms in populations differ from one another in terms of many traits that tend to be passed on from parent to offspring. Darwin's brilliant insight was to combine these two factors and to realize that success in the struggle for existence would not be determined by chance, but instead would be biased by some of the heritable differences that exist among organisms. Specifically, he noted that some individuals happen to possess traits that make them slightly better suited to a particular environment, meaning that they are more likely to survive than individuals with less well suited traits. As a result, organisms with these traits will, on average, leave more offspring than their competitors.

Whereas the origin of a new genetic variant occurs at random in terms of its effects on the organism, the probability of it being passed on to the next generation is absolutely non-random if it impacts the survival and reproductive capabilities of that organism. The important point is that this is a two-step process: first, the origin of variation by random mutation, and second, the non-random sorting of variation due to its effects on survival and reproduction (Mayr 2001 ). Though definitions of natural selection have been phrased in many ways (Table  1 ), it is this non-random difference in survival and reproduction that forms the basis of the process.

Darwinian Fitness

The meaning of fitness in evolutionary biology.

In order to study the operation and effects of natural selection, it is important to have a means of describing and quantifying the relationships between genotype (gene complement), phenotype (physical and behavioral features), survival, and reproduction in particular environments. The concept used by evolutionary biologists in this regard is known as “Darwinian fitness,” which is defined most simply as a measure of the total (or relative) reproductive output of an organism with a particular genotype (Table  1 ). In the most basic terms, one can state that the more offspring an individual produces, the higher is its fitness. It must be emphasized that the term “fitness,” as used in evolutionary biology, does not refer to physical condition, strength, or stamina and therefore differs markedly from its usage in common language.

“Survival of the Fittest” is Misleading

In the fifth edition of the Origin (published in 1869), Darwin began using the phrase “survival of the fittest”, which had been coined a few years earlier by British economist Herbert Spencer, as shorthand for natural selection. This was an unfortunate decision as there are several reasons why “survival of the fittest” is a poor descriptor of natural selection. First, in Darwin's context, “fittest” implied “best suited to a particular environment” rather than “most physically fit,” but this crucial distinction is often overlooked in non-technical usage (especially when further distorted to “only the strong survive”). Second, it places undue emphasis on survival: While it is true that dead organisms do not reproduce, survival is only important evolutionarily insofar as it affects the number of offspring produced. Traits that make life longer or less difficult are evolutionarily irrelevant unless they also influence reproductive output. Indeed, traits that enhance net reproduction may increase in frequency over many generations even if they compromise individual longevity. Conversely, differences in fecundity alone can create differences in fitness, even if survival rates are identical among individuals. Third, this implies an excessive focus on organisms, when in fact traits or their underlying genes equally can be identified as more or less fit than alternatives. Lastly, this phrase is often misconstrued as being circular or tautological (Who survives? The fittest. Who are the fittest? Those who survive). However, again, this misinterprets the modern meaning of fitness, which can be both predicted in terms of which traits are expected to be successful in a specific environment and measured in terms of actual reproductive success in that environment.

Which Traits Are the Most Fit?

Directional natural selection can be understood as a process by which fitter traits (or genes) increase in proportion within populations over the course of many generations. It must be understood that the relative fitness of different traits depends on the current environment. Thus, traits that are fit now may become unfit later if the environment changes. Conversely, traits that have now become fit may have been present long before the current environment arose, without having conferred any advantage under previous conditions. Finally, it must be noted that fitness refers to reproductive success relative to alternatives here and now —natural selection cannot increase the proportion of traits solely because they may someday become advantageous. Careful reflection on how natural selection actually works should make it clear why this is so.

Natural Selection and Adaptive Evolution

Natural selection and the evolution of populations.

Though each has been tested and shown to be accurate, none of the observations and inferences that underlies natural selection is sufficient individually to provide a mechanism for evolutionary change Footnote 6 . Overproduction alone will have no evolutionary consequences if all individuals are identical. Differences among organisms are not relevant unless they can be inherited. Genetic variation by itself will not result in natural selection unless it exerts some impact on organism survival and reproduction. However, any time all of Darwin's postulates hold simultaneously—as they do in most populations—natural selection will occur. The net result in this case is that certain traits (or, more precisely, genetic variants that specify those traits) will, on average , be passed on from one generation to the next at a higher rate than existing alternatives in the population. Put another way, when one considers who the parents of the current generation were, it will be seen that a disproportionate number of them possessed traits beneficial for survival and reproduction in the particular environment in which they lived.

The important points are that this uneven reproductive success among individuals represents a process that occurs in each generation and that its effects are cumulative over the span of many generations. Over time, beneficial traits will become increasingly prevalent in descendant populations by virtue of the fact that parents with those traits consistently leave more offspring than individuals lacking those traits. If this process happens to occur in a consistent direction—say, the largest individuals in each generation tend to leave more offspring than smaller individuals—then there can be a gradual, generation-by-generation change in the proportion of traits in the population. This change in proportion and not the modification of organisms themselves is what leads to changes in the average value of a particular trait in the population. Organisms do not evolve; populations evolve.

The term “adaptation” derives from ad + aptus , literally meaning “toward + fit”. As the name implies, this is the process by which populations of organisms evolve in such a way as to become better suited to their environments as advantageous traits become predominant. On a broader scale, it is also how physical, physiological, and behavioral features that contribute to survival and reproduction (“adaptations”) arise over evolutionary time. This latter topic is particularly difficult for many to grasp, though of course a crucial first step is to understand the operation of natural selection on smaller scales of time and consequence. (For a detailed discussion of the evolution of complex organs such as eyes, see Gregory 2008b .)

On first pass, it may be difficult to see how natural selection can ever lead to the evolution of new characteristics if its primary effect is merely to eliminate unfit traits. Indeed, natural selection by itself is incapable of producing new traits, and in fact (as many readers will have surmised), most forms of natural selection deplete genetic variation within populations. How, then, can an eliminative process like natural selection ever lead to creative outcomes?

To answer this question, one must recall that evolution by natural selection is a two-step process. The first step involves the generation of new variation by mutation and recombination, whereas the second step determines which randomly generated variants will persist into the next generation. Most new mutations are neutral with respect to survival and reproduction and therefore are irrelevant in terms of natural selection (but not, it must be pointed out, to evolution more broadly). The majority of mutations that have an impact on survival and reproductive output will do so negatively and, as such, will be less likely than existing alternatives to be passed on to subsequent generations. However, a small percentage of new mutations will turn out to have beneficial effects in a particular environment and will contribute to an elevated rate of reproduction by organisms possessing them. Even a very slight advantage is sufficient to cause new beneficial mutations to increase in proportion over the span of many generations.

Biologists sometimes describe beneficial mutations as “spreading” or “sweeping” through a population, but this shorthand is misleading. Rather, beneficial mutations simply increase in proportion from one generation to the next because, by definition, they happen to contribute to the survival and reproductive success of the organisms carrying them. Eventually, a beneficial mutation may be the only alternative left as all others have ultimately failed to be passed on. At this point, that beneficial genetic variant is said to have become “fixed” in the population.

Again, mutation does not occur in order to improve fitness—it merely represents errors in genetic replication. This means that most mutations do not improve fitness: There are many more ways of making things worse than of making them better. It also means that mutations will continue to occur even after previous beneficial mutations have become fixed. As such, there can be something of a ratcheting effect in which beneficial mutations arise and become fixed by selection, only to be supplemented later by more beneficial mutations which, in turn, become fixed. All the while, neutral and deleterious mutations also occur in the population, the latter being passed on at a lower rate than alternatives and often being lost before reaching any appreciable frequency.

Of course, this is an oversimplification—in species with sexual reproduction, multiple beneficial mutations may be brought together by recombination such that the fixation of beneficial genes need not occur sequentially. Likewise, recombination can juxtapose deleterious mutations, thereby hastening their loss from the population. Nonetheless, it is useful to imagine the process of adaptation as one in which beneficial mutations arise continually (though perhaps very infrequently and with only minor positive impacts) and then accumulate in the population over many generations.

The process of adaptation in a population is depicted in very basic form in Fig.  2 . Several important points can be drawn from even such an oversimplified rendition:

Mutations are the source of new variation. Natural selection itself does not create new traits; it only changes the proportion of variation that is already present in the population. The repeated two-step interaction of these processes is what leads to the evolution of novel adaptive features.

Mutation is random with respect to fitness. Natural selection is, by definition, non-random with respect to fitness. This means that, overall, it is a serious misconception to consider adaptation as happening “by chance”.

Mutations occur with all three possible outcomes: neutral, deleterious, and beneficial. Beneficial mutations may be rare and deliver only a minor advantage, but these can nonetheless increase in proportion in the population over many generations by natural selection. The occurrence of any particular beneficial mutation may be very improbable, but natural selection is very effective at causing these individually unlikely improvements to accumulate. Natural selection is an improbability concentrator.

No organisms change as the population adapts. Rather, this involves changes in the proportion of beneficial traits across multiple generations.

The direction in which adaptive change occurs is dependent on the environment. A change in environment can make previously beneficial traits neutral or detrimental and vice versa.

Adaptation does not result in optimal characteristics. It is constrained by historical, genetic, and developmental limitations and by trade-offs among features (see Gregory 2008b ).

It does not matter what an “ideal” adaptive feature might be—the only relevant factor is that variants that happen to result in greater survival and reproduction relative to alternative variants are passed on more frequently. As Darwin wrote in a letter to Joseph Hooker (11 Sept. 1857), “I have just been writing an audacious little discussion, to show that organic beings are not perfect, only perfect enough to struggle with their competitors.”

The process of adaptation by natural selection is not forward-looking, and it cannot produce features on the grounds that they might become beneficial sometime in the future. In fact, adaptations are always to the conditions experienced by generations in the past.

A highly simplified depiction of natural selection ( Correct ) and a generalized illustration of various common misconceptions about the mechanism ( Incorrect ). Properly understood, natural selection occurs as follows: ( A ) A population of organisms exhibits variation in a particular trait that is relevant to survival in a given environment. In this diagram, darker coloration happens to be beneficial, but in another environment, the opposite could be true. As a result of their traits, not all individuals in Generation 1 survive equally well, meaning that only a non-random subsample ultimately will succeed in reproducing and passing on their traits ( B ). Note that no individual organisms in Generation 1 change, rather the proportion of individuals with different traits changes in the population. The individuals who survive from Generation 1 reproduce to produce Generation 2. ( C ) Because the trait in question is heritable, this second generation will (mostly) resemble the parent generation. However, mutations have also occurred, which are undirected (i.e., they occur at random in terms of the consequences of changing traits), leading to both lighter and darker offspring in Generation 2 as compared to their parents in Generation 1. In this environment, lighter mutants are less successful and darker mutants are more successful than the parental average. Once again, there is non-random survival among individuals in the population, with darker traits becoming disproportionately common due to the death of lighter individuals ( D ). This subset of Generation 2 proceeds to reproduce. Again, the traits of the survivors are passed on, but there is also undirected mutation leading to both deleterious and beneficial differences among the offspring ( E ). ( F ) This process of undirected mutation and natural selection (non-random differences in survival and reproductive success) occurs over many generations, each time leading to a concentration of the most beneficial traits in the next generation. By Generation N , the population is composed almost entirely of very dark individuals. The population can now be said to have become adapted to the environment in which darker traits are the most successful. This contrasts with the intuitive notion of adaptation held by most students and non-biologists. In the most common version, populations are seen as uniform, with variation being at most an anomalous deviation from the norm ( X ). It is assumed that all members within a single generation change in response to pressures imposed by the environment ( Y ). When these individuals reproduce, they are thought to pass on their acquired traits. Moreover, any changes that do occur due to mutation are imagined to be exclusively in the direction of improvement ( Z ). Studies have revealed that it can be very difficult for non-experts to abandon this intuitive interpretation in favor of a scientifically valid understanding of the mechanism. Diagrams based in part on Bishop and Anderson ( 1990 )

Natural Selection Is Elegant, Logical, and Notoriously Difficult to Grasp

The extent of the problem.

In its most basic form, natural selection is an elegant theory that effectively explains the obviously good fit of living things to their environments. As a mechanism, it is remarkably simple in principle yet incredibly powerful in application. However, the fact that it eluded description until 150 years ago suggests that grasping its workings and implications is far more challenging than is usually assumed.

Three decades of research have produced unambiguous data revealing a strikingly high prevalence of misconceptions about natural selection among members of the public and in students at all levels, from elementary school pupils to university science majors (Alters 2005 ; Bardapurkar 2008 ; Table  2 ) Footnote 7 . A finding that less than 10% of those surveyed possess a functional understanding of natural selection is not atypical. It is particularly disconcerting and undoubtedly exacerbating that confusions about natural selection are common even among those responsible for teaching it Footnote 8 . As Nehm and Schonfeld ( 2007 ) recently concluded, “one cannot assume that biology teachers with extensive backgrounds in biology have an accurate working knowledge of evolution, natural selection, or the nature of science.”

Why is Natural Selection so Difficult to Understand?

Two obvious hypotheses present themselves for why misunderstandings of natural selection are so widespread. The first is that understanding the mechanism of natural selection requires an acceptance of the historical fact of evolution, the latter being rejected by a large fraction of the population. While an improved understanding of the process probably would help to increase overall acceptance of evolution, surveys indicate that rates of acceptance already are much higher than levels of understanding. And, whereas levels of understanding and acceptance may be positively correlated among teachers (Vlaardingerbroek and Roederer 1997 ; Rutledge and Mitchell 2002 ; Deniz et al. 2008 ), the two parameters seem to be at most only very weakly related in students Footnote 9 (Bishop and Anderson 1990 ; Demastes et al. 1995 ; Brem et al. 2003 ; Sinatra et al. 2003 ; Ingram and Nelson 2006 ; Shtulman 2006 ). Teachers notwithstanding, “it appears that a majority on both sides of the evolution-creation debate do not understand the process of natural selection or its role in evolution” (Bishop and Anderson 1990 ).

The second intuitive hypothesis is that most people simply lack formal education in biology and have learned incorrect versions of evolutionary mechanisms from non-authoritative sources (e.g., television, movies, parents). Inaccurate portrayals of evolutionary processes in the media, by teachers, and by scientists themselves surely exacerbate the situation (e.g., Jungwirth 1975a , b , 1977 ; Moore et al. 2002 ). However, this alone cannot provide a full explanation, because even direct instruction on natural selection tends to produce only modest improvements in students' understanding (e.g., Jensen and Finley 1995 ; Ferrari and Chi 1998 ; Nehm and Reilly 2007 ; Spindler and Doherty 2009 ). There also is evidence that levels of understanding do not differ greatly between science majors and non-science majors (Sundberg and Dini 1993 ). In the disquieting words of Ferrari and Chi ( 1998 ), “misconceptions about even the basic principles of Darwin's theory of evolution are extremely robust, even after years of education in biology.”

Misconceptions are well known to be common with many (perhaps most) aspects of science, including much simpler and more commonly encountered phenomena such as the physics of motion (e.g., McCloskey et al. 1980 ; Halloun and Hestenes 1985 ; Bloom and Weisberg 2007 ). The source of this larger problem seems to be a significant disconnect between the nature of the world as reflected in everyday experience and the one revealed by systematic scientific investigation (e.g., Shtulman 2006 ; Sinatra et al. 2008 ). Intuitive interpretations of the world, though sufficient for navigating daily life, are usually fundamentally at odds with scientific principles. If common sense were more than superficially accurate, scientific explanations would be less counterintuitive, but they also would be largely unnecessary.

Conceptual Frameworks Versus Spontaneous Constructions

It has been suggested by some authors that young students simply are incapable of understanding natural selection because they have not yet developed the formal reasoning abilities necessary to grasp it (Lawson and Thompson 1988 ). This could be taken to imply that natural selection should not be taught until later grades; however, those who have studied student understanding directly tend to disagree with any such suggestion (e.g., Clough and Wood-Robinson 1985 ; Settlage 1994 ). Overall, the issue does not seem to be a lack of logic (Greene 1990 ; Settlage 1994 ), but a combination of incorrect underlying premises about mechanisms and deep-seated cognitive biases that influence interpretations.

Many of the misconceptions that block an understanding of natural selection develop early in childhood as part of “naïve” but practical understandings of how the world is structured. These tend to persist unless replaced with more accurate and equally functional information. In this regard, some experts have argued that the goal of education should be to supplant existing conceptual frameworks with more accurate ones (see Sinatra et al. 2008 ). Under this view, “Helping people to understand evolution...is not a matter of adding on to their existing knowledge, but helping them to revise their previous models of the world to create an entirely new way of seeing” (Sinatra et al. 2008 ). Other authors suggest that students do not actually maintain coherent conceptual frameworks relating to complex phenomena, but instead construct explanations spontaneously using intuitions derived from everyday experience (see Southerland et al. 2001 ). Though less widely accepted, this latter view gains support from the observation that naïve evolutionary explanations given by non-experts may be tentative and inconsistent (Southerland et al. 2001 ) and may differ depending on the type of organisms being considered (Spiegel et al. 2006 ). In some cases, students may attempt a more complex explanation but resort to intuitive ideas when they encounter difficulty (Deadman and Kelly 1978 ). In either case, it is abundantly clear that simply describing the process of natural selection to students is ineffective and that it is imperative that misconceptions be confronted if they are to be corrected (e.g., Greene 1990 ; Scharmann 1990 ; Settlage 1994 ; Ferrari and Chi 1998 ; Alters and Nelson 2002 ; Passmore and Stewart 2002 ; Alters 2005 ; Nelson 2007 ).

A Catalog of Common Misconceptions

Whereas the causes of cognitive barriers to understanding remain to be determined, their consequences are well documented. It is clear from many studies that complex but accurate explanations of biological adaptation typically yield to naïve intuitions based on common experience (Fig.  2 ; Tables  2 and 3 ). As a result, each of the fundamental components of natural selection may be overlooked or misunderstood when it comes time to consider them in combination, even if individually they appear relatively straightforward. The following sections provide an overview of the various, non-mutually exclusive, and often correlated misconceptions that have been found to be most common. All readers are encouraged to consider these conceptual pitfalls carefully in order that they may be avoided. Teachers, in particular, are urged to familiarize themselves with these errors so that they may identify and address them among their students.

Teleology and the “Function Compunction”

Much of the human experience involves overcoming obstacles, achieving goals, and fulfilling needs. Not surprisingly, human psychology includes a powerful bias toward thoughts about the “purpose” or “function” of objects and behaviors—what Kelemen and Rosset ( 2009 ) dub the “human function compunction.” This bias is particularly strong in children, who are apt to see most of the world in terms of purpose; for example, even suggesting that “rocks are pointy to keep animals from sitting on them” (Kelemen 1999a , b ; Kelemen and Rosset 2009 ). This tendency toward explanations based on purpose (“teleology”) runs very deep and persists throughout high school (Southerland et al. 2001 ) and even into postsecondary education (Kelemen and Rosset 2009 ). In fact, it has been argued that the default mode of teleological thinking is, at best, suppressed rather than supplanted by introductory scientific education. It therefore reappears easily even in those with some basic scientific training; for example, in descriptions of ecological balance (“fungi grow in forests to help decomposition”) or species survival (“finches diversified in order to survive”; Kelemen and Rosset 2009 ).

Teleological explanations for biological features date back to Aristotle and remain very common in naïve interpretations of adaptation (e.g., Tamir and Zohar 1991 ; Pedersen and Halldén 1992 ; Southerland et al. 2001 ; Sinatra et al. 2008 ; Table  2 ). On the one hand, teleological reasoning may preclude any consideration of mechanisms altogether if simply identifying a current function for an organ or behavior is taken as sufficient to explain its existence (e.g., Bishop and Anderson 1990 ). On the other hand, when mechanisms are considered by teleologically oriented thinkers, they are often framed in terms of change occurring in response to a particular need (Table  2 ). Obviously, this contrasts starkly with a two-step process involving undirected mutations followed by natural selection (see Fig.  2 and Table  3 ).

Anthropomorphism and Intentionality

A related conceptual bias to teleology is anthropomorphism, in which human-like conscious intent is ascribed either to the objects of natural selection or to the process itself (see below). In this sense, anthropomorphic misconceptions can be characterized as either internal (attributing adaptive change to the intentional actions of organisms) or external (conceiving of natural selection or “Nature” as a conscious agent; e.g., Kampourakis and Zogza 2008 ; Sinatra et al. 2008 ).

Internal anthropomorphism or “intentionality” is intimately tied to the misconception that individual organisms evolve in response to challenges imposed by the environment (rather than recognizing evolution as a population-level process). Gould ( 1980 ) described the obvious appeal of such intuitive notions as follows:

Since the living world is a product of evolution, why not suppose that it arose in the simplest and most direct way? Why not argue that organisms improve themselves by their own efforts and pass these advantages to their offspring in the form of altered genes—a process that has long been called, in technical parlance, the “inheritance of acquired characters.” This idea appeals to common sense not only for its simplicity but perhaps even more for its happy implication that evolution travels an inherently progressive path, propelled by the hard work of organisms themselves.

The penchant for seeing conscious intent is often sufficiently strong that it is applied not only to non-human vertebrates (in which consciousness, though certainly not knowledge of genetics and Darwinian fitness, may actually occur), but also to plants and even to single-celled organisms. Thus, adaptations in any taxon may be described as “innovations,” “inventions,” or “solutions” (sometimes “ingenious” ones, no less). Even the evolution of antibiotic resistance is characterized as a process whereby bacteria “learn” to “outsmart” antibiotics with frustrating regularity. Anthropomorphism with an emphasis on forethought is also behind the common misconception that organisms behave as they do in order to enhance the long-term well-being of their species. Once again, a consideration of the actual mechanics of natural selection should reveal why this is fallacious.

All too often, an anthropomorphic view of evolution is reinforced with sloppy descriptions by trusted authorities (Jungwirth 1975a , b , 1977 ; Moore et al. 2002 ). Consider this particularly egregious example from a website maintained by the National Institutes of Health Footnote 10 :

As microbes evolve, they adapt to their environment. If something stops them from growing and spreading—such as an antimicrobial—they evolve new mechanisms to resist the antimicrobials by changing their genetic structure. Changing the genetic structure ensures that the offspring of the resistant microbes are also resistant.

Fundamentally inaccurate descriptions such as this are alarmingly common. As a corrective, it is a useful exercise to translate such faulty characterizations into accurate language Footnote 11 . For example, this could read:

Bacteria that cause disease exist in large populations, and not all individuals are alike. If some individuals happen to possess genetic features that make them resistant to antibiotics, these individuals will survive the treatment while the rest gradually are killed off. As a result of their greater survival, the resistant individuals will leave more offspring than susceptible individuals, such that the proportion of resistant individuals will increase each time a new generation is produced. When only the descendants of the resistant individuals are left, the population of bacteria can be said to have evolved resistance to the antibiotics.

Use and Disuse

Many students who manage to avoid teleological and anthropomorphic pitfalls nonetheless conceive of evolution as involving change due to use or disuse of organs. This view, which was developed explicitly by Jean-Baptiste Lamarck but was also invoked to an extent by Darwin ( 1859 ), emphasizes changes to individual organisms that occur as they use particular features more or less. For example, Darwin ( 1859 ) invoked natural selection to explain the loss of sight in some subterranean rodents, but instead favored disuse alone as the explanation for loss of eyes in blind, cave-dwelling animals: “As it is difficult to imagine that eyes, though useless, could be in any way injurious to animals living in darkness, I attribute their loss wholly to disuse.” This sort of intuition remains common in naïve explanations for why unnecessary organs become vestigial or eventually disappear. Modern evolutionary theory recognizes several reasons that may account for the loss of complex features (e.g., Jeffery 2005 ; Espinasa and Espinasa 2008 ), some of which involve direct natural selection, but none of which is based simply on disuse.

Soft Inheritance

Evolution involving changes in individual organisms, whether based on conscious choice or use and disuse, would require that characteristics acquired during the lifetime of an individual be passed on to offspring Footnote 12 , a process often termed “soft inheritance.” The notion that acquired traits can be transmitted to offspring remained a common assumption among thinkers for more than 2,000 years, including into Darwin's time (Zirkle 1946 ). As is now understood, inheritance is actually “hard,” meaning that physical changes that occur during an organism's lifetime are not passed to offspring. This is because the cells that are involved in reproduction (the germline) are distinct from those that make up the rest of the body (the somatic line); only changes that affect the germline can be passed on. New genetic variants arise through mutation and recombination during replication and will often only exert their effects in offspring and not in the parents in whose reproductive cells they occur (though they could also arise very early in development and appear later in the adult offspring). Correct and incorrect interpretations of inheritance are contrasted in Fig.  3 .

A summary of correct ( left ) and incorrect ( right ) conceptions of heredity as it pertains to adaptive evolutionary change. The panels on the left display the operation of “hard inheritance”, whereas those on the right illustrate naïve mechanisms of “soft inheritance”. In all diagrams, a set of nine squares represents an individual multicellular organism and each square represents a type of cell of which the organisms are constructed. In the left panels, the organisms include two kinds of cells: those that produce gametes (the germline, black ) and those that make up the rest of the body (the somatic line, white ). In the top left panel , all cells in a parent organism initially contain a gene that specifies white coloration marked W ( A ). A random mutation occurs in the germline, changing the gene from one that specifies white to one that specifies gray marked G ( B ). This mutant gene is passed to the egg ( C ), which then develops into an offspring exhibiting gray coloration ( D ). The mutation in this case occurred in the parent (specifically, in the germline) but its effects did not become apparent until the next generation. In the bottom left panel , a parent once again begins with white coloration and the white gene in all of its cells ( H ). During its lifetime, the parent comes to acquire a gray coloration due to exposure to particular environmental conditions ( I ). However, because this does not involve any change to the genes in the germline, the original white gene is passed into the egg ( J ), and the offspring exhibits none of the gray coloration that was acquired by its parent ( K ). In the top right panel , the distinction between germline and somatic line is not understood. In this case, a parent that initially exhibits white coloration ( P ) changes during its lifetime to become gray ( Q ). Under incorrect views of soft inheritance, this altered coloration is passed on to the egg ( R ), and the offspring is born with the gray color acquired by its parent ( S ). In the bottom right panel , a more sophisticated but still incorrect view of inheritance is shown. Here, traits are understood to be specified by genes, but no distinction is recognized between the germline and somatic line. In this situation, a parent begins with white coloration and white-specifying genes in all its cells ( W ). A mutation occurs in one type of body cells to change those cells to gray ( X ). A mixture of white and gray genes is passed on to the egg ( Y ), and the offspring develops white coloration in most cells but gray coloration in the cells where gray-inducing mutations arose in the parent ( Z ). Intuitive ideas regarding soft inheritance underlie many misconceptions of how adaptive evolution takes place (see Fig.  2 )

Studies have indicated that belief in soft inheritance arises early in youth as part of a naïve model of heredity (e.g., Deadman and Kelly 1978 ; Kargbo et al. 1980 ; Lawson and Thompson 1988 ; Wood-Robinson 1994 ). That it seems intuitive probably explains why the idea of soft inheritance persisted so long among prominent thinkers and why it is so resistant to correction among modern students. Unfortunately, a failure to abandon this belief is fundamentally incompatible with an appreciation of evolution by natural selection as a two-step process in which the origin of new variation and its relevance to survival in a particular environment are independent considerations.

Nature as a Selecting Agent

Thirty years ago, widely respected broadcaster Sir David Attenborough ( 1979 ) aptly described the challenge of avoiding anthropomorphic shorthand in descriptions of adaptation:

Darwin demonstrated that the driving force of [adaptive] evolution comes from the accumulation, over countless generations, of chance genetical changes sifted by the rigors of natural selection. In describing the consequences of this process it is only too easy to use a form of words that suggests that the animals themselves were striving to bring about change in a purposeful way–that fish wanted to climb onto dry land, and to modify their fins into legs, that reptiles wished to fly, strove to change their scales into feathers and so ultimately became birds.

Unlike many authors, Attenborough ( 1979 ) admirably endeavored to not use such misleading terminology. However, this quote inadvertently highlights an additional challenge in describing natural selection without loaded language. In it, natural selection is described as a “driving force” that rigorously “sifts” genetic variation, which could be misunderstood to imply that it takes an active role in prompting evolutionary change. Much more seriously, one often encounters descriptions of natural selection as a processes that “chooses” among “preferred” variants or “experiments with” or “explores” different options. Some expressions, such as “favored” and “selected for” are used commonly as shorthand in evolutionary biology and are not meant to impart consciousness to natural selection; however, these too may be misinterpreted in the vernacular sense by non-experts and must be clarified.

Darwin ( 1859 ) himself could not resist slipping into the language of agency at times:

It may be said that natural selection is daily and hourly scrutinizing, throughout the world, every variation, even the slightest; rejecting that which is bad, preserving and adding up all that is good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life. We see nothing of these slow changes in progress, until the hand of time has marked the long lapse of ages, and then so imperfect is our view into long past geological ages, that we only see that the forms of life are now different from what they formerly were.

Perhaps recognizing the ease with which such language can be misconstrued, Darwin ( 1868 ) later wrote that “The term ‘Natural Selection’ is in some respects a bad one, as it seems to imply conscious choice; but this will be disregarded after a little familiarity.” Unfortunately, more than “a little familiarity” seems necessary to abandon the notion of Nature as an active decision maker.

Being, as it is, the simple outcome of differences in reproductive success due to heritable traits, natural selection cannot have plans, goals, or intentions, nor can it cause changes in response to need. For this reason, Jungwirth ( 1975a , b , 1977 ) bemoaned the tendency for authors and instructors to invoke teleological and anthropomorphic descriptions of the process and argued that this served to reinforce misconceptions among students (see also Bishop and Anderson 1990 ; Alters and Nelson 2002 ; Moore et al. 2002 ; Sinatra et al. 2008 ). That said, a study of high school students by Tamir and Zohar ( 1991 ) suggested that older students can recognize the distinction between an anthropomorphic or teleological formulation (i.e., merely a convenient description) versus an anthropomorphic/teleological explanation (i.e., involving conscious intent or goal-oriented mechanisms as causal factors; see also Bartov 1978 , 1981 ). Moore et al. ( 2002 ), by contrast, concluded from their study of undergraduates that “students fail to distinguish between the relatively concrete register of genetics and the more figurative language of the specialist shorthand needed to condense the long view of evolutionary processes” (see also Jungwirth 1975a , 1977 ). Some authors have argued that teleological wording can have some value as shorthand for describing complex phenomena in a simple way precisely because it corresponds to normal thinking patterns, and that contrasting this explicitly with accurate language can be a useful exercise during instruction (Zohar and Ginossar 1998 ). In any case, biologists and instructors should be cognizant of the risk that linguistic shortcuts may send students off track.

Source Versus Sorting of Variation

Intuitive models of evolution based on soft inheritance are one-step models of adaptation: Traits are modified in one generation and appear in their altered form in the next. This is in conflict with the actual two-step process of adaptation involving the independent processes of mutation and natural selection. Unfortunately, many students who eschew soft inheritance nevertheless fail to distinguish natural selection from the origin of new variation (e.g., Greene 1990 ; Creedy 1993 ; Moore et al. 2002 ). Whereas an accurate understanding recognizes that most new mutations are neutral or harmful in a given environment, such naïve interpretations assume that mutations occur as a response to environmental challenges and therefore are always beneficial (Fig.  2 ). For example, many students may believe that exposure to antibiotics directly causes bacteria to become resistant, rather than simply changing the relative frequencies of resistant versus non-resistant individuals by killing off the latter Footnote 13 . Again, natural selection itself does not create new variation, it merely influences the proportion of existing variants. Most forms of selection reduce the amount of genetic variation within populations, which may be counteracted by the continual emergence of new variation via undirected mutation and recombination.

Typological, Essentialist, and Transformationist Thinking

Misunderstandings about how variation arises are problematic, but a common failure to recognize that it plays a role at all represents an even a deeper concern. Since Darwin ( 1859 ), evolutionary theory has been based strongly on “population” thinking that emphasizes differences among individuals. By contrast, many naïve interpretations of evolution remain rooted in the “typological” or “essentialist” thinking that has existed since the ancient Greeks (Mayr 1982 , 2001 ; Sinatra et al. 2008 ). In this case, species are conceived of as exhibiting a single “type” or a common “essence,” with variation among individuals representing anomalous and largely unimportant deviations from the type or essence. As Shtulman ( 2006 ) notes, “human beings tend to essentialize biological kinds and essentialism is incompatible with natural selection.” As with many other conceptual biases, the tendency to essentialize seems to arise early in childhood and remains the default for most individuals (Strevens 2000 ; Gelman 2004 ; Evans et al. 2005 ; Shtulman 2006 ).

The incorrect belief that species are uniform leads to “transformationist” views of adaptation in which an entire population transforms as a whole as it adapts (Alters 2005 ; Shtulman 2006 ; Bardapurkar 2008 ). This contrasts with the correct, “variational” understanding of natural selection in which it is the proportion of traits within populations that changes (Fig.  2 ). Not surprisingly, transformationist models of adaptation usually include a tacit assumption of soft inheritance and one-step change in response to challenges. Indeed, Shtulman ( 2006 ) found that transformationists appeal to “need” as a cause of evolutionary change three times more often than do variationists.

Events and Absolutes Versus Processes and Probabilities

A proper understanding of natural selection recognizes it as a process that occurs within populations over the course of many generations. It does so through cumulative, statistical effects on the proportion of traits differing in their consequences for reproductive success. This contrasts with two major errors that are commonly incorporated into naïve conceptions of the process:

Natural selection is mistakenly seen as an event rather than as a process (Ferrari and Chi 1998 ; Sinatra et al. 2008 ). Events generally have a beginning and end, occur in a specific sequential order, consist of distinct actions, and may be goal-oriented. By contrast, natural selection actually occurs continually and simultaneously within entire populations and is not goal-oriented (Ferrari and Chi 1998 ). Misconstruing selection as an event may contribute to transformationist thinking as adaptive changes are thought to occur in the entire population simultaneously. Viewing natural selection as a single event can also lead to incorrect “saltationist” assumptions in which complex adaptive features are imagined to appear suddenly in a single generation (see Gregory 2008b for an overview of the evolution of complex organs).

Natural selection is incorrectly conceived as being “all or nothing,” with all unfit individuals dying and all fit individuals surviving. In actuality, it is a probabilistic process in which some traits make it more likely—but do not guarantee—that organisms possessing them will successfully reproduce. Moreover, the statistical nature of the process is such that even a small difference in reproductive success (say, 1%) is enough to produce a gradual increase in the frequency of a trait over many generations.

Concluding Remarks

Surveys of students at all levels paint a bleak picture regarding the level of understanding of natural selection. Though it is based on well-established and individually straightforward components, a proper grasp of the mechanism and its implications remains very rare among non-specialists. The unavoidable conclusion is that the vast majority of individuals, including most with postsecondary education in science, lack a basic understanding of how adaptive evolution occurs.

While no concrete solutions to this problem have yet been found, it is evident that simply outlining the various components of natural selection rarely imparts an understanding of the process to students. Various alternative teaching strategies and activities have been suggested, and some do help to improve the level of understanding among students (e.g., Bishop and Anderson 1986 ; Jensen and Finley 1995 , 1996 ; Firenze 1997 ; Passmore and Stewart 2002 ; Sundberg 2003 ; Alters 2005 ; Scharmann 1990 ; Wilson 2005 ; Nelson 2007 , 2008 ; Pennock 2007 ; Kampourakis and Zogza 2008 ). Efforts to integrate evolution throughout biology curricula rather than segregating it into a single unit may also prove more effective (Nehm et al. 2009 ), as may steps taken to make evolution relevant to everyday concerns (e.g., Hillis 2007 ).

At the very least, it is abundantly clear that teaching and learning natural selection must include efforts to identify, confront, and supplant misconceptions. Most of these derive from deeply held conceptual biases that may have been present since childhood. Natural selection, like most complex scientific theories, runs counter to common experience and therefore competes—usually unsuccessfully—with intuitive ideas about inheritance, variation, function, intentionality, and probability. The tendency, both outside and within academic settings, to use inaccurate language to describe evolutionary phenomena probably serves to reinforce these problems.

Natural selection is a central component of modern evolutionary theory, which in turn is the unifying theme of all biology. Without a grasp of this process and its consequences, it is simply impossible to understand, even in basic terms, how and why life has become so marvelously diverse. The enormous challenge faced by biologists and educators in correcting the widespread misunderstanding of natural selection is matched only by the importance of the task.

For a more advanced treatment, see Bell ( 1997 , 2008 ) or consult any of the major undergraduate-level evolutionary biology or population genetics textbooks.

The Origin was, in Darwin's words, an “abstract” of a much larger work he had initially intended to write. Much of the additional material is available in Darwin ( 1868 ) and Stauffer ( 1975 ).

See Gregory ( 2008a ) for a discussion regarding the use of the term “theory” in science.

Ridley ( 2004 ) points out that Darwin's calculations require overlapping generations to reach this exact number, but the point remains that even in slow-reproducing species the rate of potential production is enormous relative to actual numbers of organisms.

Humans are currently undergoing a rapid population expansion, but this is the exception rather than the rule. As Darwin ( 1859 ) noted, “Although some species may now be increasing, more or less rapidly, in numbers, all cannot do so, for the world would not hold them.”

It cannot be overemphasized that “evolution” and “natural selection” are not interchangeable. This is because not all evolution occurs by natural selection and because not all outcomes of natural selection involve changes in the genetic makeup of populations. A detailed discussion of the different types of selection is beyond the scope of this article, but it can be pointed out that the effect of “stabilizing selection” is to prevent directional change in populations.

Instructors interested in assessing their own students' level of understanding may wish to consult tests developed by Bishop and Anderson ( 1986 ), Anderson et al. ( 2002 ), Beardsley ( 2004 ), Shtulman ( 2006 ), or Kampourakis and Zogza ( 2009 ).

Even more alarming is a recent indication that one in six teachers in the USA is a young Earth creationist, and that about one in eight teaches creationism as though it were a valid alternative to evolutionary science (Berkman et al. 2008 ).

Strictly speaking, it is not necessary to understand how evolution occurs to be convinced that it has occurred because the historical fact of evolution is supported by many convergent lines of evidence that are independent of discussions about particular mechanisms. Again, this represents the important distinction between evolution as fact and theory. See Gregory ( 2008a ).

http://www3.niaid.nih.gov/topics/antimicrobialResistance/Understanding/history.htm , accessed February 2009.

One should always be wary of the linguistic symptoms of anthropomorphic misconceptions, which usually include phrasing like “so that” (versus “because”) or “in order to” (versus “happened to”) when explaining adaptations (Kampourakis and Zogza 2009 ).

It must be noted that the persistent tendency to label the inheritance of acquired characteristics as “Lamarckian” is false: Soft inheritance was commonly accepted long before Lamarck's time (Zirkle 1946 ). Likewise, mechanisms involving organisms' conscious desires to change are often incorrectly attributed to Lamarck. For recent critiques of the tendency to describe various misconceptions as Lamarckian, see Geraedts and Boersma ( 2006 ) and Kampourakis and Zogza ( 2007 ). It is unfortunate that these mistakenly attributed concepts serve as the primary legacy of Lamarck, who in actuality made several important contributions to biology (a term first used by Lamarck), including greatly advancing the classification of invertebrates (another term he coined) and, of course, developing the first (albeit ultimately incorrect) mechanistic theory of evolution. For discussions of Lamarck's views and contributions to evolutionary biology, see Packard ( 1901 ), Burkhardt ( 1972 , 1995 ), Corsi ( 1988 ), Humphreys ( 1995 , 1996 ), and Kampourakis and Zogza ( 2007 ). Lamarck's works are available online at http://www.lamarck.cnrs.fr/index.php?lang=en .

One may wonder how this misconception is reconciled with the common admonition by medical doctors to complete each course of treatment with antibiotics even after symptoms disappear—would this not provide more opportunities for bacteria to “develop” resistance by prolonging exposure?

Alters B. Teaching biological evolution in higher education. Boston: Jones and Bartlett; 2005.

Google Scholar  

Alters BJ, Nelson CE. Teaching evolution in higher education. Evolution. 2002;56:1891–901.

Anderson DL, Fisher KM, Norman GJ. Development and evaluation of the conceptual inventory of natural selection. J Res Sci Teach. 2002;39:952–78. doi: 10.1002/tea.10053 .

Asghar A, Wiles JR, Alters B. Canadian pre-service elementary teachers' conceptions of biological evolution and evolution education. McGill J Educ. 2007;42:189–209.

Attenborough D. Life on earth. Boston: Little, Brown and Company; 1979.

Banet E, Ayuso GE. Teaching of biological inheritance and evolution of living beings in secondary school. Int J Sci Edu 2003;25:373–407.

Bardapurkar A. Do students see the “selection” in organic evolution? A critical review of the causal structure of student explanations. Evo Edu Outreach. 2008;1:299–305. doi: 10.1007/s12052-008-0048-5 .

Barton NH, Briggs DEG, Eisen JA, Goldstein DB, Patel NH. Evolution. Cold Spring Harbor: Cold Spring Harbor Laboratory Press; 2007.

Bartov H. Can students be taught to distinguish between teleological and causal explanations? J Res Sci Teach. 1978;15:567–72. doi: 10.1002/tea.3660150619 .

Bartov H. Teaching students to understand the advantages and disadvantages of teleological and anthropomorphic statements in biology. J Res Sci Teach. 1981;18:79–86. doi: 10.1002/tea.3660180113 .

Beardsley PM. Middle school student learning in evolution: are current standards achievable? Am Biol Teach. 2004;66:604–12. doi: 10.1662/0002-7685(2004)066[0604:MSSLIE]2.0.CO;2 .

Bell G. The basics of selection. New York: Chapman & Hall; 1997.

Bell G. Selection: the mechanism of evolution. 2nd ed. Oxford: Oxford University Press; 2008.

Berkman MB, Pacheco JS, Plutzer E. Evolution and creationism in America's classrooms: a national portrait. PLoS Biol. 2008;6:e124. doi: 10.1371/journal.pbio.0060124 .

Bishop BA, Anderson CW. Evolution by natural selection: a teaching module (Occasional Paper No. 91). East Lansing: Institute for Research on Teaching; 1986.

Bishop BA, Anderson CW. Student conceptions of natural selection and its role in evolution. J Res Sci Teach. 1990;27:415–27. doi: 10.1002/tea.3660270503 .

Bizzo NMV. From Down House landlord to Brazilian high school students: what has happened to evolutionary knowledge on the way? J Res Sci Teach. 1994;31:537–56.

Bloom P, Weisberg DS. Childhood origins of adult resistance to science. Science. 2007;316:996–7. doi: 10.1126/science.1133398 .

CAS   Google Scholar  

Brem SK, Ranney M, Schindel J. Perceived consequences of evolution: college students perceive negative personal and social impact in evolutionary theory. Sci Educ. 2003;87:181–206. doi: 10.1002/sce.10105 .

Brumby M. Problems in learning the concept of natural selection. J Biol Educ. 1979;13:119–22.

Brumby MN. Misconceptions about the concept of natural selection by medical biology students. Sci Educ. 1984;68:493–503. doi: 10.1002/sce.3730680412 .

Burkhardt RW. The inspiration of Lamarck's belief in evolution. J Hist Biol. 1972;5:413–38. doi: 10.1007/BF00346666 .

Burkhardt RW. The spirit of system. Cambridge: Harvard University Press; 1995.

Chinsamy A, Plaganyi E. Accepting evolution. Evolution. 2007;62:248–54.

Clough EE, Wood-Robinson C. How secondary students interpret instances of biological adaptation. J Biol Educ. 1985;19:125–30.

Corsi P. The age of Lamarck. Berkeley: University of California Press; 1988.

Coyne JA. Selling Darwin. Nature. 2006;442:983–4. doi: 10.1038/442983a .

Creedy LJ. Student understanding of natural selection. Res Sci Educ. 1993;23:34–41. doi: 10.1007/BF02357042 .

Curry A. Creationist beliefs persist in Europe. Science. 2009;323:1159. doi: 10.1126/science.323.5918.1159 .

Darimont CT, Carlson SM, Kinnison MT, Paquet PC, Reimchen TE, Wilmers CC. Human predators outpace other agents of trait change in the wild. Proc Natl Acad Sci U S A. 2009;106:952–4. doi: 10.1073/pnas.0809235106 .

Darwin C. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray; 1859.

Darwin, C. The variation of animals and plants under domestication. London: John Murray; 1868.

Darwin C, Wallace AR. On the tendency of species to form varieties; and on the perpetuation of varieties and species by natural means of selection. Proc Linn Soc. 1858;3:46–62.

Deadman JA, Kelly PJ. What do secondary school boys understand about evolution and heredity before they are taught the topic? J Biol Educ. 1978;12:7–15.

Demastes SS, Settlage J, Good R. Students' conceptions of natural selection and its role in evolution: cases of replication and comparison. J Res Sci Teach. 1995;32:535–50. doi: 10.1002/tea.3660320509 .

Deniz H, Donelly LA, Yilmaz I. Exploring the factors related to acceptance of evolutionary theory among Turkish preservice biology teachers: toward a more informative conceptual ecology for biological evolution. J Res Sci Teach. 2008;45:420–43. doi: 10.1002/tea.20223 .

Dennett DC. Darwin's dangerous idea. New York: Touchstone Books; 1995.

Espinasa M, Espinasa L. Losing sight of regressive evolution. Evo Edu Outreach. 2008;1:509–16. doi: 10.1007/s12052-008-0094-z .

Evans EM, Mull MS, Poling DA, Szymanowski K. Overcoming an essentialist bias: from metamorphosis to evolution. In Biennial meeting of the Society for Research in Child Development , Atlanta, GA; 2005.

Evans EM, Spiegel A, Gram W, Frazier BF, Thompson S, Tare M, Diamond J. A conceptual guide to museum visitors’ understanding of evolution. In Annual Meeting of the American Education Research Association , San Francisco; 2006.

Ferrari M, Chi MTH. The nature of naive explanations of natural selection. Int J Sci Educ. 1998;20:1231–56. doi: 10.1080/0950069980201005 .

Firenze R. Lamarck vs. Darwin: dueling theories. Rep Natl Cent Sci Educ. 1997;17:9–11.

Freeman S, Herron JC. Evolutionary analysis. 4th ed. Upper Saddle River: Prentice Hall; 2007.

Futuyma DJ. Evolution. Sunderland: Sinauer; 2005.

Gelman SA. Psychological essentialism in children. Trends Cogn Sci. 2004;8:404–9. doi: 10.1016/j.tics.2004.07.001 .

Geraedts CL, Boersma KT. Reinventing natural selection. Int J Sci Educ. 2006;28:843–70. doi: 10.1080/09500690500404722 .

Gould SJ. Shades of Lamarck. In: The Panda's Thumb. New York: Norton; 1980. p. 76–84.

Greene ED. The logic of university students' misunderstanding of natural selection. J Res Sci Teach. 1990;27:875–85. doi: 10.1002/tea.3660270907 .

Gregory TR. Evolution as fact, theory, and path. Evo Edu Outreach. 2008a;1:46–52. doi: 10.1007/s12052-007-0001-z .

Gregory TR. The evolution of complex organs. Evo Edu Outreach. 2008b;1:358–89. doi: 10.1007/s12052-008-0076-1 .

Gregory TR. Artificial selection and domestication: modern lessons from Darwin's enduring analogy. Evo Edu Outreach. 2009;2:5–27. doi: 10.1007/s12052-008-0114-z .

Hall BK, Hallgrimsson B. Strickberger's evolution. 4th ed. Sudbury: Jones and Bartlett; 2008.

Halldén O. The evolution of the species: pupil perspectives and school perspectives. Int J Sci Educ. 1988;10:541–52. doi: 10.1080/0950069880100507 .

Halloun IA, Hestenes D. The initial knowledge state of college physics students. Am J Phys. 1985;53:1043–55. doi: 10.1119/1.14030 .

Hillis DM. Making evolution relevant and exciting to biology students. Evolution. 2007;61:1261–4. doi: 10.1111/j.1558-5646.2007.00126.x .

Humphreys J. The laws of Lamarck. Biologist. 1995;42:121–5.

Humphreys J. Lamarck and the general theory of evolution. J Biol Educ. 1996;30:295–303.

Ingram EL, Nelson CE. Relationship between achievement and students' acceptance of evolution or creation in an upper-level evolution course. J Res Sci Teach. 2006;43:7–24. doi: 10.1002/tea.20093 .

Jeffery WR. Adaptive evolution of eye degeneration in the Mexican blind cavefish. J Heredity. 2005;96:185–96. doi: 10.1093/jhered/esi028 .

Jensen MS, Finley FN. Teaching evolution using historical arguments in a conceptual change strategy. Sci Educ. 1995;79:147–66. doi: 10.1002/sce.3730790203 .

Jensen MS, Finley FN. Changes in students' understanding of evolution resulting from different curricular and instructional strategies. J Res Sci Teach. 1996;33:879–900. doi: 10.1002/(SICI)1098-2736(199610)33:8<879::AID-TEA4>3.0.CO;2-T .

Jiménez-Aleixandre MP. Thinking about theories or thinking with theories?: a classroom study with natural selection. Int J Sci Educ. 1992;14:51–61. doi: 10.1080/0950069920140106 .

Jiménez-Aleixandre MP, Fernández-Pérez J. Selection or adjustment? Explanations of university biology students for natural selection problems. In: Novak, JD. Proceedings of the Second International Seminar on Misconceptions and Educational Strategies in Science and Mathematics, vol II. Ithaca: Department of Education, Cornell University; 1987;224–32.

Jørgensen C, Enberg K, Dunlop ES, Arlinghaus R, Boukal DS, Brander K, et al. Managing evolving fish stocks. Science. 2007;318:1247–8. doi: 10.1126/science.1148089 .

Jungwirth E. The problem of teleology in biology as a problem of biology-teacher education. J Biol Educ. 1975a;9:243–6.

Jungwirth E. Preconceived adaptation and inverted evolution. Aust Sci Teachers J. 1975b;21:95–100.

Jungwirth E. Should natural phenomena be described teleologically or anthropomorphically?—a science educator’s view. J Biol Educ. 1977;11:191–6.

Kampourakis K, Zogza V. Students’ preconceptions about evolution: how accurate is the characterization as “Lamarckian” when considering the history of evolutionary thought? Sci Edu 2007;16:393–422.

Kampourakis K, Zogza V. Students’ intuitive explanations of the causes of homologies and adaptations. Sci Educ. 2008;17:27–47. doi: 10.1007/s11191-007-9075-9 .

Kampourakis K, Zogza V. Preliminary evolutionary explanations: a basic framework for conceptual change and explanatory coherence in evolution. Sci Educ. 2009; in press.

Kardong KV. An introduction to biological evolution. 2nd ed. Boston: McGraw Hill; 2008.

Kargbo DB, Hobbs ED, Erickson GL. Children's beliefs about inherited characteristics. J Biol Educ. 1980;14:137–46.

Kelemen D. Why are rocks pointy? Children's preference for teleological explanations of the natural world. Dev Psychol. 1999a;35:1440–52. doi: 10.1037/0012-1649.35.6.1440 .

Kelemen D. Function, goals and intention: children's teleological reasoning about objects. Trends Cogn Sci. 1999b;3:461–8. doi: 10.1016/S1364-6613(99)01402-3 .

Kelemen D, Rosset E. The human function compunction: teleological explanation in adults. Cognition. 2009;111:138–43. doi: 10.1016/j.cognition.2009.01.001 .

Keown D. Teaching evolution: improved approaches for unprepared students. Am Biol Teach. 1988;50:407–10.

Lawson AE, Thompson LD. Formal reasoning ability and misconceptions concerning genetics and natural selection. J Res Sci Teach. 1988;25:733–46. doi: 10.1002/tea.3660250904 .

MacFadden BJ, Dunckel BA, Ellis S, Dierking LD, Abraham-Silver L, Kisiel J, et al. Natural history museum visitors' understanding of evolution. BioScience. 2007;57:875–82.

Mayr E. The growth of biological thought. Cambridge: Harvard University Press; 1982.

Mayr E. What evolution Is. New York: Basic Books; 2001.

McCloskey M, Caramazza A, Green B. Curvilinear motion in the absence of external forces: naïve beliefs about the motion of objects. Science. 1980;210:1139–41. doi: 10.1126/science.210.4474.1139 .

Moore R, Mitchell G, Bally R, Inglis M, Day J, Jacobs D. Undergraduates' understanding of evolution: ascriptions of agency as a problem for student learning. J Biol Educ. 2002;36:65–71.

Nehm RH, Reilly L. Biology majors' knowledge and misconceptions of natural selection. BioScience. 2007;57:263–72. doi: 10.1641/B570311 .

Nehm RH, Schonfeld IS. Does increasing biology teacher knowledge of evolution and the nature of science lead to greater preference for the teaching of evolution in schools? J Sci Teach Educ. 2007;18:699–723. doi: 10.1007/s10972-007-9062-7 .

Nehm RH, Poole TM, Lyford ME, Hoskins SG, Carruth L, Ewers BE, et al. Does the segregation of evolution in biology textbooks and introductory courses reinforce students' faulty mental models of biology and evolution? Evo Edu Outreach. 2009;2: In press.

Nelson CE. Teaching evolution effectively: a central dilemma and alternative strategies. McGill J Educ. 2007;42:265–83.

Nelson CE. Teaching evolution (and all of biology) more effectively: strategies for engagement, critical reasoning, and confronting misconceptions. Integr Comp Biol. 2008;48:213–25. doi: 10.1093/icb/icn027 .

Packard AS. Lamarck, the founder of evolution: his life and work with translations of his writings on organic evolution. New York: Longmans, Green, and Co; 1901.

Palumbi SR. Humans as the world's greatest evolutionary force. Science. 2001;293:1786–90. doi: 10.1126/science.293.5536.1786 .

Passmore C, Stewart J. A modeling approach to teaching evolutionary biology in high schools. J Res Sci Teach. 2002;39:185–204. doi: 10.1002/tea.10020 .

Pedersen S, Halldén O. Intuitive ideas and scientific explanations as parts of students' developing understanding of biology: the case of evolution. Eur J Psychol Educ. 1992;9:127–37.

Pennock RT. Learning evolution and the nature of science using evolutionary computing and artificial life. McGill J Educ. 2007;42:211–24.

Prinou L, Halkia L, Skordoulis C. What conceptions do Greek school students form about biological evolution. Evo Edu Outreach. 2008;1:312–7. doi: 10.1007/s12052-008-0051-x .

Ridley M. Evolution. 3rd ed. Malden: Blackwell; 2004.

Robbins JR, Roy P. The natural selection: identifying & correcting non-science student preconceptions through an inquiry-based, critical approach to evolution. Am Biol Teach. 2007;69:460–6. doi: 10.1662/0002-7685(2007)69[460:TNSICN]2.0.CO;2 .

Rose MR, Mueller LD. Evolution and ecology of the organism. Upper Saddle River: Prentice Hall; 2006.

Rutledge ML, Mitchell MA. High school biology teachers' knowledge structure, acceptance & teaching of evolution. Am Biol Teach. 2002;64:21–7. doi: 10.1662/0002-7685(2002)064[0021:HSBTKS]2.0.CO;2 .

Scharmann LC. Enhancing an understanding of the premises of evolutionary theory: the influence of a diversified instructional strategy. Sch Sci Math. 1990;90:91–100.

Settlage J. Conceptions of natural selection: a snapshot of the sense-making process. J Res Sci Teach. 1994;31:449–57.

Shtulman A. Qualitative differences between naïve and scientific theories of evolution. Cognit Psychol. 2006;52:170–94. doi: 10.1016/j.cogpsych.2005.10.001 .

Sinatra GM, Southerland SA, McConaughy F, Demastes JW. Intentions and beliefs in students' understanding and acceptance of biological evolution. J Res Sci Teach. 2003;40:510–28. doi: 10.1002/tea.10087 .

Sinatra GM, Brem SK, Evans EM. Changing minds? Implications of conceptual change for teaching and learning about biological evolution. Evo Edu Outreach. 2008;1:189–95. doi: 10.1007/s12052-008-0037-8 .

Southerland SA, Abrams E, Cummins CL, Anzelmo J. Understanding students' explanations of biological phenomena: conceptual frameworks or p-prims? Sci Educ. 2001;85:328–48. doi: 10.1002/sce.1013 .

Spiegel AN, Evans EM, Gram W, Diamond J. Museum visitors' understanding of evolution. Museums Soc Issues. 2006;1:69–86.

Spindler LH, Doherty JH. Assessment of the teaching of evolution by natural selection through a hands-on simulation. Teach Issues Experiments Ecol. 2009;6:1–20.

Stauffer RC (editor). Charles Darwin's natural selection: being the second part of his big species book written from 1856 to 1858. Cambridge, UK: Cambridge University Press; 1975.

Stearns SC, Hoekstra RF. Evolution: an introduction. 2nd ed. Oxford, UK: Oxford University Press; 2005.

Strevens M. The essentialist aspect of naive theories. Cognition. 2000;74:149–75. doi: 10.1016/S0010-0277(99)00071-2 .

Sundberg MD. Strategies to help students change naive alternative conceptions about evolution and natural selection. Rep Natl Cent Sci Educ. 2003;23:1–8.

Sundberg MD, Dini ML. Science majors vs nonmajors: is there a difference? J Coll Sci Teach. 1993;22:299–304.

Tamir P, Zohar A. Anthropomorphism and teleology in reasoning about biological phenomena. Sci Educ. 1991;75:57–67. doi: 10.1002/sce.3730750106 .

Tidon R, Lewontin RC. Teaching evolutionary biology. Genet Mol Biol. 2004;27:124–31. doi: 10.1590/S1415-475720054000100021 .

Vlaardingerbroek B, Roederer CJ. Evolution education in Papua New Guinea: trainee teachers' views. Educ Stud. 1997;23:363–75. doi: 10.1080/0305569970230303 .

Wilson DS. Evolution for everyone: how to increase acceptance of, interest in, and knowledge about evolution. PLoS Biol. 2005;3:e364. doi: 10.1371/journal.pbio.0030364 .

Wood-Robinson C. Young people's ideas about inheritance and evolution. Stud Sci Educ. 1994;24:29–47. doi: 10.1080/03057269408560038 .

Zirkle C. The early history of the idea of the inheritance of acquired characters and of pangenesis. Trans Am Philos Soc. 1946;35:91–151. doi: 10.2307/1005592 .

Zohar A, Ginossar S. Lifting the taboo regarding teleology and anthropomorphism in biology education—heretical suggestions. Sci Educ. 1998;82:679–97. doi: 10.1002/(SICI)1098-237X(199811)82:6<679::AID-SCE3>3.0.CO;2-E .

Download references

Author information

Authors and affiliations.

Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada

T. Ryan Gregory

You can also search for this author in PubMed   Google Scholar

Corresponding author

Correspondence to T. Ryan Gregory .

Rights and permissions

Open Access This is an open access article distributed under the terms of the Creative Commons Attribution Noncommercial License ( https://creativecommons.org/licenses/by-nc/2.0 ), which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.

Reprints and permissions

About this article

Cite this article.

Gregory, T.R. Understanding Natural Selection: Essential Concepts and Common Misconceptions. Evo Edu Outreach 2 , 156–175 (2009). https://doi.org/10.1007/s12052-009-0128-1

Download citation

Received : 14 March 2009

Accepted : 16 March 2009

Published : 09 April 2009

Issue Date : June 2009

DOI : https://doi.org/10.1007/s12052-009-0128-1

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

Evolution: Education and Outreach

ISSN: 1936-6434

• Submission enquiries: [email protected]

Loading metrics

Open Access

What is adaptation by natural selection? Perspectives of an experimental microbiologist

* E-mail: [email protected]

Affiliations Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America, BEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, Michigan, United States of America

• Richard E. Lenski

Published: April 20, 2017

• https://doi.org/10.1371/journal.pgen.1006668
• Reader Comments

Ever since Darwin, the role of natural selection in shaping the morphological, physiological, and behavioral adaptations of animals and plants across generations has been central to understanding life and its diversity. New discoveries have shown with increasing precision how genetic, molecular, and biochemical processes produce and express those organismal features during an individual’s lifetime. When it comes to microorganisms, however, understanding the role of natural selection in producing adaptive solutions has historically been, and sometimes continues to be, contentious. This tension is curious because microbes enable one to observe the power of adaptation by natural selection with exceptional rigor and clarity, as exemplified by the burgeoning field of experimental microbial evolution. I trace the development of this field, describe an experiment with Escherichia coli that has been running for almost 30 years, and highlight other experiments in which natural selection has led to interesting dynamics and adaptive changes in microbial populations.

Citation: Lenski RE (2017) What is adaptation by natural selection? Perspectives of an experimental microbiologist. PLoS Genet 13(4): e1006668. https://doi.org/10.1371/journal.pgen.1006668

Editor: W. Ford Doolittle, Dalhousie University, CANADA

Copyright: © 2017 Richard E. Lenski. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: REL has been supported, in part, by a National Science Foundation grant (DEB-1451740), the BEACON Center for the Study of Evolution in Action (Cooperative Agreement DBI-0939454), and the John Hannah Endowment at Michigan State University. The funders had no role in the preparation of the article.

Competing interests: The author has declared that no competing interests exist.

Evolution, natural selection, and genetics

The fields of biology and evolution have come a long way since Charles Darwin published The Origin of Species in 1859. Nonetheless, Darwin is celebrated for the big ideas that he got right, including descent with modification and adaptation by natural selection. The former refers broadly to the fact that evolution has occurred such that organisms living today are different from their ancestors. Natural selection is the evolutionary process that explains the match, or fit, between features of organisms and the environments where they live.

Jean-Baptiste Lamarck and other natural philosophers had previously put forward the idea of evolution in the general sense of descent with modification. And Alfred Russel Wallace, a younger contemporary of Darwin, independently came up with the concept of adaptation by natural selection. Neither space nor expertise allows me to do justice to the history of these ideas, except to note that Darwin is better known today than Wallace because Darwin brought to bear an extraordinary range of relevant evidence and insights that have, by and large, stood the test of time. When Darwin was rushed at the age of 50 to publish The Origin by virtue of Wallace’s discoveries, he produced a 502-page volume rich with insights and details that he called a mere “abstract” of the great book he had intended to publish. Over his remaining years, Darwin published many more books— The Variation of Animals and Plants Under Domestication (1868), The Descent of Man , and Selection in Relation to Sex (1871), and The Expression of the Emotions in Man and Animals (1872) among them—that provided further insights and more evidence concerning his core theories of descent with modification and adaptation by natural selection.

Lamarck is now known largely for his theory of the inheritance of acquired characteristics. While Lamarckian inheritance has been soundly rejected as a general theory of biological inheritance, it seems to have foreshadowed certain special cases in biology in which an environmental agent induces an adaptive genetic change. For example, when a lysogenic phage infects a bacterium, the phage’s DNA can integrate into the bacterial chromosome and thereby confer immunity to reinfection by another phage. Similarly, CRISPR/Cas (clustered regularly interspaced short palindromic repeats/CRISPR-associated protein) systems allow bacteria and archaea to incorporate bits of DNA from phages and plasmids that provide immunity against later infections [ 1 ]. Cultural evolution in humans also occurs via acquisition from the environment (by learning) and inheritance that is, in that respect, Lamarckian. Certain maternal effects and epigenetic mechanisms are also sometimes said to be Lamarckian. However, these are special cases and different from the general theory that Lamarck proposed, which has been supplanted by modern genetics and molecular biology. Moreover, these quasi-Lamarckian special cases—at least those that confer clear benefits—presumably evolved by the Darwinian process of adaptation by natural selection.

But Darwin, too, got some things wrong. His proposed mechanism for inheritance involved “gemmules” made throughout the body and then concentrated in the reproductive organs, allowing transmission across generations in a rather Lamarckian manner. Darwin also thought the process of evolution was too slow to directly observe. In The Origin , he wrote: “We see nothing of these slow changes in progress, until the hand of time has marked the long lapse of ages, and then so imperfect is our view … that we only see that the forms of life are now different from what they formerly were.” This view seems rather surprising, given that The Origin began by discussing the process of domestication and using artificial selection as practiced by plant and animal breeders to inform the theory of natural selection. Yet even there, he wrote: “Slow and insensible changes of this kind could never be recognised unless actual measurements or careful drawings of the breeds in question had been made long ago, which might serve for comparison.”

The impact and reach of Darwin’s theories are well reflected in T. H. Huxley’s quip, “How extremely stupid not to have thought of that,” and in the title of a paper by Theodosius Dobzhansky [ 2 ]: “Nothing in biology makes sense except in the light of evolution.” However, while zoologists and botanists largely embraced adaptation by natural selection following the rediscovery of Mendelian inheritance and the rise of population genetics leading to the Modern Synthesis, many microbiologists were skeptical of its importance to the organisms they studied. For example, I. M. Lewis [ 3 ] wrote, “The subject of bacterial variation and heredity has reached an almost hopeless state of confusion … There are many advocates of the Lamarckian mode of bacterial inheritance, while others hold to the view that it is essentially Darwinian.” As a consequence, Julian Huxley [ 4 ] excluded bacteria from the Modern Synthesis in 1942, writing “They have no genes in the sense of accurately quantized portions of hereditary substance …”

That changed the very next year, however, when Salvador Luria and Max Delbrück [ 5 ] published their fluctuation test, which showed that mutations in E . coli that confer resistance to viruses could occur before exposure. That meant that natural selection was responsible for the rise in frequency of the resistant mutants following exposure but not for their mutational origin. The replica-plating experiment of Joshua and Esther Lederberg [ 6 ] provided another, even more direct, demonstration of the conceptual distinction between the origin of genetic variants by mutation and the fate of those variants, which depended on selection.

Evolution observed

Though Darwin thought evolution was too slow a process to observe directly, not all of his contemporaries agreed. In particular, William Dallinger put Darwin’s theories to the test in the 1880s. An ordained minister and future president of the Royal Microscopical Society, Dallinger built an incubator in which he cultivated three protozoan species, gradually raising the temperature over several years before an accident ended the experiment [ 7 , 8 ] ( Fig 1 ). Over time, new strains arose that grew at temperatures lethal to the original strains. One wonders, in retrospect, whether these strains were mutants, representatives of a diverse community present at the outset, or perhaps contaminants, although his account shows the great care with which he ran the experiment and monitored the organisms. In any case, this work showed how one could watch evolution in action using microorganisms. As Dallinger himself put it: “I can only claim for this fragment its suggestiveness, and its possible value as an incentive to treat the lower and minuter forms of life in corresponding manners, and as showing that such work cannot be without value.”

• PPT PowerPoint slide
• PNG larger image
• TIFF original image

Image from Dallinger (1887), now in the public domain ( http://commons.wikimedia.org/w/index.php?curid=10531922 ).

https://doi.org/10.1371/journal.pgen.1006668.g001

It would be many decades, however, before this value was fully realized. The experiments of Luria, Delbrück, and the Lederbergs had demonstrated that mutation and selection were distinct processes, but their main impact was in genetics, where they set off the revolution that became the field of molecular genetics by showing that microbes were superb models for understanding the physicochemical basis of heredity. Nonetheless, the importance of natural selection for the “minuter forms of life” took hold, albeit tenuously, as the result of key papers in the early 1950s.

Aaron Novick and Leo Szilard had worked on the Manhattan Project before their interests turned to biology. They sought to estimate mutation rates by measuring the rate at which phenotypically defined classes of mutants accumulated in E . coli populations growing in a chemostat, provided the mutants grew at the same rate as their parents. (If the mutants grew more slowly, as some did, they would reach a mutation–selection balance.) Novick and Szilard [ 9 , 10 ] saw for a while the expected linear accumulation of mutants, followed by a precipitous drop in their frequency and then a resumption of the linear increase. They hypothesized that the sudden decline in the frequency of the observed mutants reflected an unseen beneficial mutation that arose in the parental background. As the fitter mutant type swept through the population, it displaced the parent strain and the observable mutants derived from the parent. Once the fitter type had become common, then it, too, began to generate measurable numbers of the observable class of mutants. Novick and Szilard tested this hypothesis by competing two strains under the same conditions: one strain bearing the observable neutral mutation isolated before the reversal, and therefore in the parental background, and the other an unmarked strain sampled after the reversal, which was hypothesized to have a beneficial mutation. As predicted, the later strain outcompeted the earlier one, and the same outcome held when the states of the neutral mutation were reversed.

Similar experiments were performed by K. C. Atwood, Lillian Schneider, and Francis Ryan [ 11 , 12 ], who saw multiple selective sweeps and introduced the term “periodic selection” to describe the phenomenon. Among these early practitioners of experimental evolution, Ryan seems to have been especially smitten by the approach and its implications. In an article titled “Evolution Observed” for Scientific American [ 13 ], he wrote: “And so the process continued: we obtained successively fitter and fitter types through 7,000 generations. All this time the medium, i.e., the environment, was kept constant … It is sometimes contended that mutations cannot provide the raw material for evolution because they are usually deleterious. But these experiments prove that selection is a powerful force for fixing and perpetuating those rare mutations that do give an advantage.”

These insightful experiments were performed before the physical basis of heredity was known. With the discovery of the double helix by James Watson and Francis Crick in 1953, genetics research became dominated by molecular approaches, and experimental studies of microbial evolution fell largely by the wayside. As a former postdoctoral researcher with George Beadle and Edward Tatum, a mentor of Joshua Lederberg, and an active participant in the management of the Cold Spring Harbor Laboratory, Ryan was well positioned to help keep the fields of evolutionary biology and molecular genetics connected, if not united. Alas, he died in 1963 at the age of just 47.

Microbial experimental evolution redux

Even as biology became increasingly split between molecular biology and “old-fashioned” studies (including evolutionary biology, ecology, and studies of whole organisms rather than their constituent molecules), some wanderers and visionaries found fertile ground between the two camps. Carl Woese used the molecules of life to reveal the deep history and previously hidden diversity of microbes [ 14 ]. Roger Milkman [ 15 ] and Robert Selander and Bruce Levin [ 16 ] followed the lead of population geneticists in using molecular markers to understand the evolutionary processes that act on contemporary populations of bacteria in nature.

And still others conducted evolution experiments with microbes—sometimes to see what interesting adaptations they could produce, sometimes to better understand the dynamics of adaptation by natural selection. Patricia Clarke, Barry Hall, and Robert Mortlock [ 17 ] were leaders in the first group, observing how bacteria could evolve new functions by, for example, constitutively expressing a protein with promiscuous activity on a novel substrate and then adapting the protein to that substrate by subsequent mutations. Using the Qβ bacteriophage, Sol Spiegelman evolved a dramatically shortened RNA genome that could self-replicate in a cell-free medium [ 18 ].

On the dynamics front, Lin Chao, Bruce Levin, and Frank Stewart studied the diversification of coevolving phage T7 and E . coli through successive bouts of resistance and host-range mutations [ 19 ]. In a study with the yeast Saccharomyces cerevisiae , Charlotte Paquin and Julian Adams showed that nontransitive competitive interactions—where B beats A, and C beats B, but A prevails against C—could lead to long-term declines in fitness, even as each replacement was driven by natural selection [ 20 ]. Using different alleles of a core metabolic gene from natural isolates of E . coli , Daniel Dykhuizen and Daniel Hartl moved them into a common genetic background to test if they affected fitness or were selectively neutral [ 21 ].

Evolution unlimited?

I direct a long-term evolution experiment (LTEE) with E . coli . Six populations were founded in 1988 from each of two ancestral strains that differ by a neutral marker [ 22 ]. There are no plasmids or functional phages, and E . coli is not naturally transformable, so evolution is strictly asexual. Spontaneous mutations provide all the genetic variation on which natural selection acts. The populations live in a minimal medium with glucose as the limiting resource. Every day, 1% of each population is transferred to a flask containing fresh medium, where the cells grow until they exhaust the glucose and then sit in stationary phase until the next day. The 100-fold regrowth permits ~6.7 cell generations per day. Samples of each population are periodically stored frozen, and where they are available for later study. The frozen samples also allow the populations to be restarted after accidents or disruptions. At this writing, the populations have passed 66,000 generations, and the goal is to continue the experiment far into the future [ 23 ].

I had been a postdoctoral researcher with Bruce Levin, building on his work on coevolving bacteria and phage [ 19 , 24 ]. When I started my lab, I continued working on interactions of bacteria, viruses, and plasmids, asking whether the fitness costs, or tradeoffs, associated with resistance to viruses and antibiotics were fixed or, alternatively, could be ameliorated by compensatory adaptations [ 25 , 26 ]. However, the interactions were complex and the analyses difficult, so I undertook the LTEE to ask some basic questions about the process of adaptation: (i) What are the dynamics of adaptation by natural selection? Is adaptation invariably slow and gradual? Or are there periods of rapid change and stasis? For how long can fitness increase? (ii) How repeatable is adaptive evolution? Will replicate populations evolve along similar paths? Or will they find different solutions to identical environments? (iii) How are the dynamics of phenotypic and genomic evolution coupled? What functional changes are responsible for the bacteria’s adaptation by natural selection?

Dynamics of adaptation by natural selection

The dynamics are interesting, and sometimes surprising, in several respects. During the first 2,000 generations or so, the effect sizes of beneficial mutations were large and produced fitness trajectories with step-like dynamics [ 23 , 27 ]. Over longer periods, the rate of improvement slowed substantially [ 27 , 28 ]. That trend might suggest that fitness is approaching some upper bound, or asymptote. However, the fitness data are better fit by a simple two-parameter power-law model, which has no asymptote, than by an equally simple hyperbolic model [ 28 ]. Moreover, the power-law model predicts fitness levels accurately far into the future using truncated datasets [ 28 ]. And a simple dynamical model with clonal interference (i.e., competition between lineages with different beneficial mutations [ 29 ]) and diminishing-returns epistasis (i.e., beneficial mutations confer smaller advantages in more-fit than in less-fit backgrounds) generates a power-law relation [ 28 ].

Repeatability of adaptation

Over 50,000 generations, a typical population increased fitness by ~70% relative to the ancestor [ 28 ], whereas a typical pair of populations differ from one another by only a few percent [ 30 ]. Against this backdrop of predictability, however, some populations stand out in interesting ways. Half of the populations evolved hypermutable phenotypes [ 31 , 32 ], which led to slightly faster rates of fitness improvement [ 28 , 30 ]. However, several of those later evolved compensatory changes that reduced their mutability, reflecting the tension between the production of beneficial mutants that are the next big winners and the cost of producing progeny with deleterious mutations [ 32 , 33 ]. The populations also vary in whether or not they generated stable polymorphisms that sustain diversity within them. One population has two lineages that have coexisted for over 40,000 generations [ 32 , 34 ]. Their coexistence depends on crossfeeding, in which one lineage is the superior competitor for the exogenously supplied glucose and the other is better at using acetate excreted into the medium [ 34 , 35 ]. Other LTEE populations have had transiently stable polymorphisms [ 36 ], and still others appear to have remained more homogeneous [ 32 ], although metagenomic sequencing may reveal previously undetected polymorphisms.

Most strikingly, one population evolved the ability to grow on citrate at ~31,000 generations [ 37 ] ( Fig 2 ), while none of the others have done so even after 66,000 generations. Citrate has been present in the medium throughout the duration of the LTEE, where it serves as a chelating agent. In principle, citrate provides another source of carbon and energy, but one of the defining characteristics of E . coli as a species is that it cannot take up and use citrate in the presence of oxygen. Each LTEE population has tested billions of mutations over time, so the difficulty of evolving the ability to use citrate does not reflect a scarcity of mutations; moreover, the population that evolved this ability was not hypermutable when it did so [ 38 ]. Instead, the difficulty of evolving this ability reflects two issues. First, expression of the relevant transporter protein required a “promoter capture” that involved rearranging nonhomologous DNA segments to produce a new module [ 38 ]. Second, even with the new module in place, efficient growth on citrate requires certain other mutations in the genetic background [ 37 – 40 ].

Photo by Brian Baer and Neerja Hajela, Michigan State University ( http://commons.wikimedia.org/w/index.php?curid=4277502 ).

https://doi.org/10.1371/journal.pgen.1006668.g002

Coupling of phenotypic and genomic evolution

When the LTEE began, not a single bacterial genome had been sequenced, and for many years whole-genome sequencing was too costly for this project. Nevertheless, by working back from phenotypic changes to candidate genes and using other approaches, some mutations were discovered; and once a mutation was found in one population, that gene was sequenced in the others [ 41 – 46 ]. This approach revealed many examples of parallel evolution at the level of genes, but because of the ad hoc ways that genes of interest were found, it was difficult to assess the global extent of parallelism and the proportion of the accumulated mutations that were beneficial.

In time, though, it became feasible to sequence and analyze complete genomes, including, most recently, 264 clones in total from the 12 independent populations [ 32 ]. The data give an extremely strong signal of genomewide parallelism, with over 50% of nonsynonymous mutations that arose in nonhypermutable lineages concentrated in just 2% of the protein-coding genes. Significant parallelism was also seen in the hypermutable lineages, although the signal was much weaker because beneficial mutations were diluted in a larger pool of neutral and weakly deleterious mutations. While there was strong parallelism at the level of genes, there were very few cases where the exact same mutations were found in any two replicate populations. Parallelism at the level of genes, and not at the level of nucleotides, supports the inference that natural selection, rather than mutational hotspots, drove the enrichment of the point mutations. The ratio of nonsynonymous to synonymous mutations, adjusted for the number of sites at risk for each, was >10 over the first 500 generations of the LTEE and has remained >2 even in later generations, providing another strong signal of natural selection [ 32 ].

Much work remains to be done to understand the effects of these mutations. A number have been demonstrated to be beneficial by constructing and competing genotypes that differ by specific mutations [ 47 , 48 ], but how they are beneficial is often unclear. The genes with beneficial mutations include ones that encode proteins with core metabolic and regulatory functions [ 32 ]. These genes are likely to have pervasive pleiotropic and epistatic effects, contributing to the difficulty in understanding exactly how mutations in those genes benefit the cells.

An explosion of experimental evolution

The field of experimental evolution has grown tremendously in recent years. Using the Google Ngram viewer ( http://books.google.com/ngrams ) for the period from 1948–2008, the word “evolution” has trended gradually upward from ~0.003% to ~0.004%. Although used far less often, the phrase “evolution experiment” showed an ~10-fold increase in use over that period (based on a 10-year running average). It is impossible to do justice to this field here, but several recent reviews that focus on evolution experiments using microbes are available [ 49 – 51 ]. Instead, I highlight a dozen papers that illustrate the wide range of issues being studied.

Several studies have documented the emergence of complex interactions between bacterial genotypes derived from the same ancestral strain. Rainey and Travisano [ 52 ] showed that populations of Pseudomonas fluorescens rapidly diversified when cultured in static flasks but did not if the flasks were shaken. The diversification occurred because the static flasks generated environmental gradients, which allowed ecotypes with different environmental preferences to flourish. Zambrano et al. [ 53 ] starved E . coli populations and found mutants that could grow while the other cells were dying. Fiegna et al. [ 54 ] studied a mutant strain of Myxococcus xanthus that could produce spores only by exploiting other strains that made fruiting bodies. From this obligate cheater, they evolved a strain that not only made fruiting bodies and spores on its own but that also was resistant to cheating by its progenitor.

Other studies have examined the evolution of bacteriophages and the role of host–parasite coevolution. Wichman et al. [ 55 ] watched two populations of phage ϕX174 evolve at high temperature while growing on a novel host, Salmonella typhimurium , and then sequenced the phage genomes. They saw striking parallelism across the replicates, with about half of the mutations that reached high frequency identical at the nucleotide level. Paterson et al. [ 56 ] compared the rate of evolution in phage ϕ2 when its P . fluorescens host was allowed to coevolve and when the host was prevented from evolving by repeatedly restarting it from a stock culture. They found that the phage’s genome evolution was faster and more variable across replicates when its host was coevolving, consistent with Red Queen dynamics. The coevolutionary dynamic between phage λ and E . coli also enabled Meyer et al. [ 57 ] to select phage genotypes that could infect cells using a new receptor, a shift not seen in many decades of previous studies of this interaction.

A different sort of coevolution—one with major health implications—occurs when humans increase antibiotic concentrations in an effort to control bacteria. A study by Lindsey et al. [ 58 ] showed that E . coli populations could sometimes be driven to extinction by raising the concentration quickly, which prevented the bacteria from evolving the high-level resistance they reached when it was raised slowly. By contrast, Baym et al. [ 59 ] built arenas where populations of motile E . coli evolved in a stepwise fashion to grow at progressively higher antibiotic concentrations. Their time-lapse videos provide a striking demonstration of evolution in action ( http://vimeo.com/180908160/7a7d12ead6 ).

Some studies have used creative selection schemes to generate interesting adaptations. Ratcliff et al. [ 60 ] performed centrifugation to select fast-settling S . cerevisiae and evolved “snowflake” yeast with a multicellular life history ( Fig 3 ), which in turn favors a division of labor between soma and reproductive cells. Most evolution experiments select for mutants that grow faster than their competitors, whereas many real-world applications need strains with higher yields, not faster growth. Bachmann et al. [ 61 ] evolved high-yield Lactococcus lactis using a water-in-oil emulsion system. Mutants that grew more efficiently had access to the remaining resources within a droplet, thereby preventing takeover by other mutants that grew faster but less efficiently.

Confocal micrographs showing many clusters (left) and one at higher magnification (right). Colors show depth in z-axis. Unpublished images by Shane Jacobeen, Will Ratcliff, and Peter Yunker, Georgia Institute of Technology.

https://doi.org/10.1371/journal.pgen.1006668.g003

New methods for watching the dynamics of genome evolution have also advanced the field. Lang et al. [ 62 ] used metagenomic sequencing to study the dynamics of within-population polymorphisms in 40 experimental populations of yeast. Levy et al. [ 63 ] used barcodes to track lineages in an evolving yeast population, revealing thousands of beneficial mutations that initially rose in frequency but ultimately were outcompeted by the most-fit lineage.

The studies highlighted in this short review have used microbes, but many other evolution experiments employ flies, mice, and other large organisms [ 64 ]. A few evolution experiments have even been performed not in the laboratory but in natural environments [ 65 , 66 ]. And, of course, many studies of adaptation by natural selection take place without designed experiments, including the extraordinary multidecadal study of Darwin’s finches in the Galápagos by Peter and Rosemary Grant [ 67 ], as well as huge swaths of comparative biology [ 68 ]. This review only scratches one surface of the body of research on adaptation by natural selection.

Conclusions

Adaptation by natural selection has been central to biology ever since Darwin presented the idea more than 150 years ago. When coupled to theories of mutation and inheritance, it explains how organisms become fit to their environments. Microbiologists were, on the whole, slower to accept the generality of this theory than those who studied plants and animals. Following critical experiments that disentangled the effects of mutation and selection in microorganisms, and given their short generations and large populations, experimental evolution has become a highly productive approach in microbiology. Some of the experiments test specific hypotheses, while others, like the LTEE, are open-ended and explore broad questions. New technologies enhance the power of experimental evolution, which may in turn provide new opportunities for applied studies in biotechnology and medicine. As evolutionary biology continues to generate fascinating ideas and questions, experimental evolution offers one approach for examining new ideas and questions.

Acknowledgments

I thank Ford Doolittle and the American Society for Microbiology for the Jeopardy-inspired symposium that led to this article and Shane Jacobeen, Will Ratcliff, and Peter Yunker for sharing the images of the snowflake yeast.

• View Article
• PubMed/NCBI
• Google Scholar
• 4. Huxley J. Evolution: The Modern Synthesis. New York: Harper; 1942.
• 17. Mortlock RP, editor. Microorganisms as Model Systems for Studying Evolution. New York: Plenum; 1984.
• 64. Garland T Jr, Rose MR, editors. Experimental Evolution: Concepts, Methods, and Applications of Selection Experiments. Berkeley: University of California Press; 2009.
• 67. Grant PR, Grant BR. 40 Years of Evolution: Darwin’s Finches on Daphne Major Island. Princeton: Princeton University Press; 2014.
• 68. Harvey PH, Pagel MD. The Comparative Method in Evolutionary Biology. Oxford: Oxford University Press; 1991.

• Skip to primary navigation
• Skip to main content
• Skip to primary sidebar
• Skip to footer
• Image & Use Policy
• Translations

UC MUSEUM OF PALEONTOLOGY

Understanding Evolution

Your one-stop source for information on evolution

• ES en Español

Natural Selection

Natural selection is one of the basic mechanisms of evolution, along with mutation, migration, and genetic drift.

Darwin’s grand idea of evolution by natural selection is relatively simple but often misunderstood. To see how it works, imagine a population of beetles:

If you have variation, differential reproduction, and heredity, you will have evolution by natural selection as an outcome. It is as simple as that.

• More Details
• Evo Examples
• Teaching Resources

See how the simple mechanisms of natural selection can  produce complex structures , learn about  misconceptions regarding natural selection , or review the history of the idea of natural selection .

Learn more about natural selection in context:

• Angling for evolutionary answers: The work of David O. Conover , a research profile.
• Battling bacterial evolution: The work of Carl Bergstrom , a research profile.
• Natural slection from the gene up: The work of Elizabeth Dahlhoff and Nathan Rank , a research profile.

Teach your students about natural selection:

• Clipbirds , a classroom activity for grades 6-12.
• Breeding bunnies , a classroom activity for grades 9-12.

Find  additional lessons, activities, videos, and articles  that focus on natural selection.

Reviewed and updated June, 2020.

Genetic drift

Natural selection at work

Subscribe to our newsletter

• Teaching resource database
• Correcting misconceptions
• Conceptual framework and NGSS alignment
• Image and use policy
• Evo in the News
• The Tree Room
• Browse learning resources

If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

To log in and use all the features of Khan Academy, please enable JavaScript in your browser.

AP®︎/College Biology

Course: ap®︎/college biology   >   unit 7.

• Introduction to evolution and natural selection
• Natural selection and the owl butterfly
• Biodiversity and natural selection
• Variation in a species

Darwin, evolution, & natural selection

Natural selection.

Key points:

• Charles Darwin was a British naturalist who proposed the theory of biological evolution by natural selection.
• Darwin defined evolution as "descent with modification," the idea that species change over time, give rise to new species, and share a common ancestor.
• The mechanism that Darwin proposed for evolution is natural selection . Because resources are limited in nature, organisms with heritable traits that favor survival and reproduction will tend to leave more offspring than their peers, causing the traits to increase in frequency over generations.
• Natural selection causes populations to become adapted , or increasingly well-suited, to their environments over time. Natural selection depends on the environment and requires existing heritable variation in a group.

What is evolution?

Early ideas about evolution, influences on darwin, darwin and the voyage of the beagle.

• Traits are often heritable. In living organisms, many characteristics are inherited, or passed from parent to offspring. (Darwin knew this was the case, even though he did not know that traits were inherited via genes.)
• More offspring are produced than can survive. Organisms are capable of producing more offspring than their environments can support. Thus, there is competition for limited resources in each generation.
• Offspring vary in their heritable traits. The offspring in any generation will be slightly different from one another in their traits (color, size, shape, etc.), and many of these features will be heritable.
• In a population, some individuals will have inherited traits that help them survive and reproduce (given the conditions of the environment, such as the predators and food sources present). The individuals with the helpful traits will leave more offspring in the next generation than their peers, since the traits make them more effective at surviving and reproducing.
• Because the helpful traits are heritable, and because organisms with these traits leave more offspring, the traits will tend to become more common (present in a larger fraction of the population) in the next generation.
• Over generations, the population will become adapted to its environment (as individuals with traits helpful in that environment have consistently greater reproductive success than their peers).

Example: How natural selection can work

Key points about natural selection, natural selection depends on the environment, natural selection acts on existing heritable variation, heritable variation comes from random mutations, natural selection and the evolution of species, attribution:, works cited:.

• Wilkin, D. and Akre, B. (2016, March 23). Influences on Darwin - Advanced. In CK-12 biology advanced concepts . Retrieved from http://www.ck12.org/book/CK-12-Biology-Advanced-Concepts/section/10.18/ .
• Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., and Jackson, R. B. (2011). The voyage of the Beagle . In Campbell Biology (10th ed., p. 466). San Francisco, CA: Pearson.
• Darwin's finches. (2016, April 25). Retrieved March 16, 2016 from Wikipedia: https://en.wikipedia.org/wiki/Darwin%27s_finches .
• Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., and Jackson, R. B. (2011). Figure 1.18. Natural selection. In Campbell biology (10th ed., p. 14). San Francisco, CA: Pearson.

Additional references:

Want to join the conversation.

• Upvote Button navigates to signup page
• Downvote Button navigates to signup page
• Flag Button navigates to signup page

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

• View all journals
• Explore content
• About the journal
• Publish with us
• Sign up for alerts
• Books & Arts
• Published: 09 May 2012

Natural selection: The evolutionary struggle

• Andrew Berry 1  

Nature volume  485 ,  pages 171–172 ( 2012 ) Cite this article

4412 Accesses

2 Citations

3 Altmetric

Metrics details

• Evolutionary theory
• Scientific community

This article has been updated

Andrew Berry enjoys a biographical feast that turns the spotlight onto Darwin's forerunners.

Darwin's Ghosts: In Search of the First Evolutionists

• Rebecca Stott

It is remarkable that the theory of evolution has come to be associated exclusively with Charles Darwin. Even Alfred Russel Wallace, co-author of the paper that first unveiled evolution by natural selection, has mostly disappeared from view. In Darwin's Ghosts , novelist and science historian Rebecca Stott explores the intellectual origins of the theory of natural selection through scientific biographies of Darwin's antecedents and contemporaries, from Aristotle to Wallace.

The usual suspects are here, including French naturalists Jean-Baptiste Lamarck, Georges Cuvier and Georges-Louis Leclerc, Count of Buffon. But so are people whose contributions to the history of evolutionary theory are generally known only in history of science departments, such as Swiss biologist Abraham Trembley and French natural historian Benoît de Maillet. Stott's research is broad and unerring; her book is wonderful.

On the Origin of Species (John Murray, 1859) was rushed out. In June 1858, Darwin got a letter from Wallace, then in Indonesia, suggesting the idea — evolution by natural selection — that Darwin had been quietly gestating for 20 years. Only intervention by colleagues saved Darwin's claim to precedence. The outcomes were a paper co-published by Darwin and Wallace in the Journal of the Proceedings of the Linnean Society in July 1858, and Origin in November the next year.

After the publication, Darwin's materialistic vision of biological change was, as he had feared, condemned as heretical. But blasphemy was not the only charge laid at his door: some of Darwin's correspondents complained that he had plagiarized their work.

Darwin saw Origin as a quick and dirty synopsis of his ideas, not the planned 'big species book', as he referred to it. One casualty was a review of the literature. As Stott recounts, Darwin dealt with this oversight (and the critical letters) in 1861, by adding a review, An Historical Sketch of the Recent Progress of Opinion on the Origin of Species , to the third edition. Stott's book presents encounters with the inhabitants of this addendum, plus a few who did not make Darwin's cut.

The Sketch was an honest attempt to give credit where it was due. But it is clear that Darwin was keen, by omission, to emphasize his own claim to the theory. Wallace is mentioned just four times in the 490 pages of the first edition of Origin . And in his autobiography, Darwin downplayed the influence of his grandfather, Erasmus Darwin, whose evolutionary speculations were both historically significant and part of his family's lore.

In looking beyond Darwin, Stott deals with eye-wateringly complicated material. A three-way chapter on Lamarck, Cuvier and fellow French naturalist Étienne Geoffroy, for instance, describes — with a novelist's eye for dramatic detail — how, in the early nineteenth century, they jockeyed for pre-eminence at the newly formed French National Museum of Natural History in Paris.

More than the story of three careers, this is also about the waxing and waning of friendships, a clash of deeply opposed world views and some of the most exciting and innovative science ever done. And the story is complicated by difficulties in interpreting the documentary record, which is mostly a monument to courtesy. Cuvier long suppressed his unfavourable view of Lamarck, waiting instead to bury both Lamarck's ideas and their author with a single brutal obituary, published in the Memoirs of the Royal Academy of Sciences of the Institute of France in 1835.

Stott highlights the charged moment when Cuvier first examined mummified ibises collected by Geoffroy on the Napoleonic expedition to Egypt. Here was the ultimate showdown between Lamarck's evolutionary ideas, which predicted that ibises should have experienced species change in the 3,000 years since the specimens were alive, and Cuvier's insistence that this was biologically impossible. Were the ancient ibis mummies significantly different from modern birds? No — Cuvier seemed to have been proved right.

Many of the heroes of Darwin's Ghosts ran risks to pursue their evolutionary ideas — in 1749, for example, French philosopher Denis Diderot was imprisoned for subversive writings that touched on species variation. Many thinkers tried to sidestep the charge of heresy: de Maillet, for example, distanced himself by presenting his theories in the form of a supposed conversation with an Indian mystic, 'Telliamed' (de Maillet spelled backwards). Erasmus Darwin, anxious about the impact of controversy on his reputation as a doctor, chose to veil many of his evolutionary speculations behind a cloak of classics-tinged poetry. Scottish geologist Robert Chambers never publicly admitted that he was the author of the anonymous Victorian best-seller Vestiges of the Natural History of Creation (John Churchill, 1848).

The lesson of Stott's book is that Darwin and Wallace were not just standing on the shoulders of giants scientifically. They were also at liberty to speculate and publish freely on the topic only because of the risks that these earlier writers had taken.

Stott introduces us to a sparkling cast of characters, but the biographical approach has its limitations. The book fails to illuminate the most remarkable aspect of the story of the discovery of evolution: that this long-sought-after idea was discovered independently, around the same time, by two men who both regarded themselves as pedestrian thinkers.

The Darwin–Wallace story validates the modern insistence that discovery is not about 'great men', but about a confluence of societal and technological factors that collectively make a previously inaccessible idea accessible. Nevertheless, Stott's constellation of biographies is an exhilarating romp through 2,000 years of fascinating scientific history.

Change history

18 may 2012.

This article originally gave the title of a publication as Journal of the Linnean Society , when it should have been Journal of the Proceedings of the Linnean Society . This has now been corrected.

Author information

Authors and affiliations.

Andrew Berry is a lecturer in evolutionary biology and teaches history of science at Harvard University in Cambridge, Massachusetts.,

Andrew Berry

You can also search for this author in PubMed   Google Scholar

Corresponding author

Correspondence to Andrew Berry .

Rights and permissions

Reprints and permissions

About this article

Cite this article.

Berry, A. Natural selection: The evolutionary struggle. Nature 485 , 171–172 (2012). https://doi.org/10.1038/485171a

Download citation

Published : 09 May 2012

Issue Date : 10 May 2012

DOI : https://doi.org/10.1038/485171a

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

This article is cited by

New in paperback.

Nature (2013)

Careless linking of Wallace and Darwin

• K. Razi Naqvi

Nature (2012)

Quick links

• Explore articles by subject
• Guide to authors
• Editorial policies

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

ENCYCLOPEDIC ENTRY

Natural selection.

Natural selection is the process through which species adapt to their environments. It is the engine that drives evolution.

On the Origin of Species

English naturalist Charles Darwin wrote the definitive book outlining his idea of natural selection, On the Origin of Species. The book chronicled his studies in South America and Pacific islands. Published in 1859, the book became a best seller.

Photograph by Ian Forsyth via Getty Images

English naturalist Charles Darwin developed the idea of natural selection after a five-year voyage to study plants, animals, and fossils in South America and on islands in the Pacific. In 1859, he brought the idea of natural selection to the attention of the world in his best-selling book, On the Origin of Species .

Natural selection is the process through which populations of living organisms adapt and change. Individuals in a population are naturally variable, meaning that they are all different in some ways. This variation means that some individuals have traits better suited to the environment than others. Individuals with adaptive traits — traits that give them some advantage—are more likely to survive and reproduce. These individuals then pass the adaptive traits on to their offspring. Over time, these advantageous traits become more common in the population. Through this process of natural selection , favorable traits are transmitted through generations .

Natural selection can lead to speciation , where one species gives rise to a new and distinctly different species . It is one of the processes that drives evolution and helps to explain the diversity of life on Earth.

Darwin chose the name natural selection to contrast with “artificial selection,” or selective breeding that is controlled by humans. He pointed to the pastime of pigeon breeding, a popular hobby in his day, as an example of artificial selection. By choosing which pigeons mated with others, hobbyists created distinct pigeon breeds, with fancy feathers or acrobatic flight, that were different from wild pigeons.

Darwin and other scientists of his day argued that a process much like artificial selection happened in nature, without any human intervention. He argued that natural selection explained how a wide variety of life forms developed over time from a single common ancestor.

Darwin did not know that genes existed, but he could see that many traits are heritable—passed from parents to offspring.

Mutations are changes in the structure of the molecules that make up genes , called DNA . The mutation of genes is an important source of genetic variation within a population. Mutations can be random (for example, when replicating cells make an error while copying DNA ), or happen as a result of exposure to something in the environment, like harmful chemicals or radiation.

Mutations can be harmful, neutral, or sometimes helpful, resulting in a new, advantageous trait. When mutations occur in germ cells (eggs and sperm), they can be passed on to offspring.

If the environment changes rapidly, some species may not be able to adapt fast enough through natural selection . Through studying the fossil record, we know that many of the organisms that once lived on Earth are now extinct. Dinosaurs are one example. An invasive species , a disease organism, a catastrophic environmental change, or a highly successful predator can all contribute to the extinction of species .

Today, human actions such as overhunting and the destruction of habitats are the main cause of extinctions. Extinctions seem to be occurring at a much faster rate today than they did in the past, as shown in the fossil record.

Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Production Managers

Program specialists, last updated.

October 19, 2023

User Permissions

For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource.

If a media asset is downloadable, a download button appears in the corner of the media viewer. If no button appears, you cannot download or save the media.

Text on this page is printable and can be used according to our Terms of Service .

Interactives

Any interactives on this page can only be played while you are visiting our website. You cannot download interactives.

Related Resources

Articles on Natural selection

Displaying 1 - 20 of 65 articles.

It’s reassuring to think humans are evolution’s ultimate destination – but research shows we may be an accident

Matthew Wills , University of Bath and Marcello Ruta , University of Lincoln

Male rhesus macaques often have sex with each other – a trait they have inherited in part from their parents

Jackson Clive , Imperial College London ; Ewan Flintham , Université de Lausanne , and Vincent Savolainen , Imperial College London

By ‘helping’ wild animals, you could end their freedom or even their lives – here’s why you should keep your distance

Julian Avery , Penn State

Ancient humans may have paused in Arabia for 30,000 years on their way out of Africa

Ray Tobler , Australian National University ; Shane T Grey , Garvan Institute , and Yassine Souilmi , University of Adelaide

Animals learn survival tricks from others – even if they live alone

Mike Webster , University of St Andrews

Why prey animals often see threats where there are none – and how it costs them

Leah Gray , University of Aberdeen and Mike Webster , University of St Andrews

How the omicron subvariant BA.5 became a master of disguise – and what it means for the current COVID-19  surge

Suresh V. Kuchipudi , Penn State

Why do hammerhead sharks have hammer-shaped heads?

Gavin Naylor , University of Florida

Wild animals are evolving faster than anybody thought

Timothée Bonnet , Australian National University

Genetic mutations can be benign or cancerous – a new method to differentiate between them could lead to better treatments

Ryan Layer , University of Colorado Boulder

Future evolution: from looks to brains and personality, how will humans change in the next 10,000 years?

Nicholas R. Longrich , University of Bath

Fig wasp sex ratios show that not all of nature is by design

Jaco Greeff , University of Pretoria and Jan Willem Helenus Ferguson , University of Pretoria

Massive numbers of new COVID–19 infections, not vaccines, are the main driver of new coronavirus variants

Vaughn Cooper , University of Pittsburgh and Lee Harrison , University of Pittsburgh

How humans became the best throwers on the planet

Michael P. Lombardo , Grand Valley State University and Robert Deaner , Grand Valley State University

Guide to the classics: Darwin’s The Descent of Man 150 years on — sex, race and our ‘lowly’ ape ancestry

Ian Hesketh , The University of Queensland and Henry-James Meiring , The University of Queensland

Vampire finches: how little birds in the Galápagos evolved to drink blood

Kiyoko Gotanda , University of Cambridge ; Daniel Baldassarre , State University of New York Oswego , and Jaime Chaves , San Francisco State University

The evolution of fairness will drive the distribution of COVID-19 vaccines, for better or worse

Justin Jennings , University of Toronto

W.E.B. Du Bois embraced science to fight racism as editor of NAACP’s magazine The Crisis

Jordan Besek , University at Buffalo

Homosexuality may have evolved for social, not sexual reasons

Andrew Barron , Macquarie University

What is sex really for?

Richard Gunderman , Indiana University

Related Topics

• Charles Darwin
• DNA mutations
• Evolutionary biology
• Human evolution

Top contributors

Professor of Evolutionary Biology and Science Engagement, University of East Anglia

Fellow, Keele University

Lecturer, School of Biology, University of St Andrews

Professor in Evolutionary Biology, Macquarie University

Vice Chancellor's Research Fellow, Edith Cowan University

Associate Professor, North Carolina State University

Distinguished Professor of Genetics and Vice Chancellor's Fellow, La Trobe University

Emeritus Professor of Animal Genetics, University of Sydney

Professor, Macquarie University

Professor, ESCP Business School

Professor of Strategy, Economics and Foresights, Hult International Business School

Professor, School of Life and Environmental Sciences, University of Sydney

PhD Researcher in Marine Ecology, University of Exeter

Honorary Associate Professor in Vision and Computational Neuroscience, University of Sheffield

Chancellor's Professor of Medicine, Liberal Arts, and Philanthropy, Indiana University

• X (Twitter)
• Unfollow topic Follow topic

Change Password

Your password must have 8 characters or more and contain 3 of the following:.

• a lower case character, 
• an upper case character, 
• a special character 

Password Changed Successfully

Your password has been changed

• Sign in / Register

Request Username

Can't sign in? Forgot your username?

Enter your email address below and we will send you your username

If the address matches an existing account you will receive an email with instructions to retrieve your username

Six Classroom Exercises to Teach Natural Selection to Undergraduate Biology Students

• Steven T. Kalinowski
• Mary J. Leonard
• Tessa M. Andrews
• Andrea R. Litt

Address correspondence to: Steven T. Kalinowski ( E-mail Address: [email protected] ).

*Department of Ecology, Montana State University, Bozeman, MT 59717

Search for more papers by this author

Department of Education, Montana State University, Bozeman, MT 59717

Students in introductory biology courses frequently have misconceptions regarding natural selection. In this paper, we describe six activities that biology instructors can use to teach undergraduate students in introductory biology courses how natural selection causes evolution. These activities begin with a lesson introducing students to natural selection and also include discussions on sexual selection, molecular evolution, evolution of complex traits, and the evolution of behavior. The set of six topics gives students the opportunity to see how natural selection operates in a variety of contexts. Pre- and postinstruction testing showed students’ understanding of natural selection increased substantially after completing this series of learning activities. Testing throughout this unit showed steadily increasing student understanding, and surveys indicated students enjoyed the activities.

INTRODUCTION

Evolution is the unifying theory of biology ( Dobzhansky, 1973 ). It also may be the most well-supported scientific theory that is rejected by a large proportion of Americans (e.g., Miller et al. , 2006 ). This high-profile controversy will be familiar to any instructor teaching evolution in the United States. What many biology instructors may not realize is the theory of evolution is also conceptually difficult for students to understand. In particular, natural selection, the main cause of evolution, is a challenging concept for many students. This is ironic, because, as many authors have emphasized (e.g., Coyne, 2009 , p. xvi), natural selection is not a complicated process.

The main reason students often have trouble understanding natural selection is that they have misconceptions regarding what causes populations to change. By “misconception,” we mean a commonly held idea that is inconsistent with scientific understanding and is resistant to instruction (sensu Hammer, 1996 ). The origin and cognitive structures that give rise to student misconceptions are the subject of ongoing research (e.g., Hammer, 1996 ; diSessa, 2006 ; Mason, 2007 ; Abrams and Southerland, 2010 ), but the actual misconceptions students have are well documented (see Gregory [2009 ] for an excellent introduction to the large literature on student misconceptions relating to natural selection). Most misconceptions relating to natural selection are variations of the belief that individuals evolve. Students often believe individuals change because they need to, because they want to, because the environment changes them, or because they use or do not use specific body parts—and that these changes are passed on to offspring (e.g., Brumby, 1984 ; Bishop and Anderson, 1990 ; Nehm and Schonfeld, 2008 ). These misconceptions are frequently similar to Lamarck's (1809) pre-Darwinian theory of evolution.

Student misconceptions regarding natural selection are remarkably resistant to instruction (for reviews, see Tanner and Allen, 2005 ; Sinatra et al. , 2008 ; Gregory, 2009 ). Bishop and Anderson (1990) showed that half of the students in an introductory biology course left the course with misconceptions regarding natural selection—even though the lectures and laboratory exercises in the course were designed specifically to address misconceptions. Nehm and Reilly (2007) found that 70% of biology majors completing an introductory biology course had at least one misconception regarding natural selection—even though the instructors emphasized evolution as a theme throughout the course and used active-learning exercises extensively to promote learning. Andrews et al. (2011b) studied the effectiveness of introductory biology courses throughout the United States and found that pre- and postinstructional measures of student understanding of natural selection in many courses were statistically identical.

Carefully designed instruction is necessary to help students replace misconceptions with scientifically supported conceptions. There is a consensus among science educators that active learning is more successful than traditional lectures in developing student understanding. Active learning essentially occurs when an instructor stops lecturing and students work on a question or task designed to help them understand a concept ( Andrews et al. , 2011b ). A classic example is a think–pair–share discussion, in which students first individually think about a question posed by the instructor, then pair up with other students to discuss the question, and finally share answers in a whole-class discussion. Students can learn twice as much when lectures contain discussions than when instructors simply lecture (e.g., Hake, 1998 ; Knight and Wood, 2005 ; Haak et al. , 2011 ). However, such active-learning instruction may not be sufficient for replacing persistent misconceptions unless instructors design learning activities that specifically focus on helping students move beyond misconceptions to scientifically supported ideas ( Duit and Treagust, 2003 ; Murphy and Mason, 2006 ; Andrews et al. , 2011b ). Ongoing research continues to identify the most effective ways to help students recognize and change misconceptions (e.g., Vosniadou, 2008 ). Nonetheless, there is a consensus that the following instructional practices are useful. First, instructors must help students become aware of what they believe and how to recognize which of their ideas conflict with observations or with previous knowledge ( Hewson et al. , 1998 ; Bransford et al. , 2000 ). Second, students are more likely to learn any concept, including ones for which they have misconceptions, when they study multiple examples of the concept at work ( Catrambone and Holyoak, 1989 ; Mestre, 2003 ; Marton, 2006 ). Third, helping students construct scientific conceptions involves introducing them to scientists’ “ways of seeing” ( Scott et al. , 1991 ); in this case, seeing situations of natural selection in terms of its genetic basis ( Kalinowski et al. , 2010 ).

There is a shortage of classroom exercises for teaching natural selection that require the active participation of students, that have been designed specifically to deal with misconceptions, and that have been shown to be effective in promoting a deep understanding of natural selection. In this investigation, we developed and assessed six classroom exercises for teaching natural selection to undergraduate students. The primary learning goal for the exercises was for students to thoroughly understand natural selection.

Participants and Context

We designed and assessed (with institutional review board permission) six lessons relating to natural selection in an introductory course on ecology and evolution during 2011 and 2012. This course was the third in a three-semester sequence of introductory biology courses for biology majors at Montana State University. The previous courses in this sequence covered physiology, cell biology, biochemistry, and genetics. Classes met three times a week for a 50-min lecture and once a week for a 3-h lab. Twenty lectures in the course were devoted to studying evolution, including six focused on natural selection.

The student body changed during our study. In 2011, 41 students enrolled in the course: 85% were freshman, 12% sophomores, and 3% seniors. In 2012, 47 students were enrolled in the course: 54% were sophomores, 29% were juniors, and 17% were seniors. The large proportion of freshman in 2011 was due to an advising error, but provided us with an unexpected opportunity to test our lessons on two different sets of students. In both years, virtually all students reported by raised hands they were preparing for careers in the health sciences.

We did not collect demographic data on race either year. However, the student body in the College of Letters of Sciences at Montana State University is 90% Caucasian, and there is no reason to suspect enrollment in this course was substantially different.

Two instructors taught the six learning activities described here. In 2011, S.T.K. taught the entire course. S.T.K. is a tenured professor, who had eight years of teaching experience in 2011. He had taught this course six times previously. In 2012, T.M.A. taught the six lectures that included the learning activities described in this paper. (S.T.K. taught the remainder of the course). At the time she taught these classes, T.M.A. was a fourth-year PhD student whose primary teaching experience consisted of serving as a teaching assistant for this course the previous year. Half of T.M.A.'s PhD research related to undergraduate biology education ( Andrews et al. , 2011a , 2011b ), so she likely had more pedagogical knowledge than most graduate students.

Description of the Six Learning Exercises

We created six learning exercises ( Table 1 ) to teach students how natural selection works and to help correct common misconceptions regarding its operation. Our exercises focused on students’ ideas, drawing from principles of active learning and conceptual change teaching. Although exercises varied, they generally included the following elements: we began by asking a thought-provoking question that asked students to account for a situation in which natural selection was occurring, to evaluate whether it was occurring, or to predict what would happen in the situation. We elicited students’ initial ideas in response to the question, either in writing or as a class discussion. We provided opportunities for students to discuss their ideas with their peers. We explicitly discussed misconceptions in ways intended to help students evaluate them; for example, describing circumstances for which a misconception could not provide an adequate explanation, facilitating students in identifying pros and cons of an explanation, and having students compare alternate explanations. Finally, we emphasized the genetic basis of natural selection by providing genetic data. The learning exercises, described below, were given in six lectures (one per lecture) in the order described below. Two of these exercises have been described previously: Kalinowski et al. (2010) described the dog-breeding discussion, and Andrews et al. (2011a) described and assessed the human evolution discussion.

Introduction to Selection: Dog Breeding.

In the first chapter of On the Origin of Species , Darwin described how plants and animals have been bred to have desired characteristics and used such “artificial” selection as an analogy to introduce how “natural” selection works in nature. The analogy is still powerful, and we used it to introduce our students to natural selection. We began this discussion by telling the class that all dog breeds are descended from wolves and asking the class “If you had a bunch of wolves and wanted a Chihuahua, how would you create one?” Students discussed the question in pairs and we then elicited answers from randomly selected students. A “correct” answer for this question is that Chihuahuas can be bred from wolves by selectively breeding small wolves with short faces and wiry tan hair for many generations. Some students provided this answer, but many proposed raising wolves in a warm environment “so they will not need such heavy fur” and providing them with plenty of food “so the wolves become less aggressive and develop smaller teeth.” Such responses reveal the misconceptions that the environment causes individuals to evolve and traits evolve from their use or disuse.

Once we recorded a diversity of answers on the board, and the class could see the need to reconcile the differences expressed, we asked students to comment on the feasibility of each proposal. This created some confusion. Some students clearly understood why raising wolves in domestic environments will not cause them to become Chihuahua-like. Others did not. We resolved the confusion by making a connection to genetics and reminding the class that wolf pups grow up to be adult wolves because they have wolf genes, not because they are raised in a forest hunting elk.

We emphasized that the selective-breeding program will work, because when a breeder preferentially chooses small, tan wolves to breed, he or she is selecting wolves with specific DNA sequences. We showed the class DNA sequences for one of the genes that differentiate Chihuahuas from wolves. Body size in wolves and dogs is influenced by variation at the insulin-like growth factor 1 ( IGF1 ) gene. Chihuahuas (and other miniature breeds) have an adenine at position 44,228,468 in the dog genome, and wolves have a guanine ( Sutter et al. , 2007 ).

After we completed the dog-breeding discussion the instructor gave a short lecture describing the requirements for natural selection. We emphasized evolution by natural selection would occur if: 1) there was phenotypic variation in a population; 2) this variation was heritable , and 3) this variation influenced the reproductive success of individuals. We repeatedly emphasized these three concepts in all our subsequent lectures, and later used them in our assessment of student learning.

Source of Variation: Coat Color in Oldfield Mice.

One of the challenges for students studying natural selection is that the genetic basis of evolution is invisible. Therefore, discussing how natural selection affects the frequency of DNA sequences in a population should be useful. Coat color in Oldfield mice, Peromyscus polionotus , makes a useful case study for how natural selection might work in the wild.

We began our discussion of coat color in Oldfield mice by describing the natural history of the species. Oldfield mice live in the southeastern United States and generally have dark fur that provides camouflage from owl predation for mice living in forests. In contrast, a subspecies of Oldfield mice, P . p . leucocephalus , lives on the white sand dunes of Santa Rosa Island on the Gulf Coast of Florida and has nearly white fur. Experiments have shown that this coloration protects mice from owls ( Kaufman, 1974 ). The difference in fur color is largely caused by a single nucleotide change in the melanocortin-1 receptor gene. Mice with a thymine at a specific location in the gene have much lighter fur than mice with a cytosine at that location ( Hoekstra et al. , 2006 ). The mice on Santa Rosa Island are the only mice in the southeastern United States with this genetic variant.

After we presented the preceding material to the class, we asked our students to consider a plausible history for Oldfield mice on Santa Rosa Island. Specifically, we asked them to assume that Oldfield mice colonized Santa Rosa Island when sea levels were lower during the last ice age, and that all of the mice colonizing the island had brown fur. We emphasized that being a brown mouse living on white sand dunes put the mouse in danger. We then asked our students “How did the population of brown mice become white?” Students thought about this question and wrote an answer on an index card. Then students discussed their answers in small groups, after which we solicited answers from the entire class. After collecting answers from several groups, we discussed the importance of mutation in creating new phenotypes, and emphasized that mutations randomly changed DNA sequences—and do not necessarily make the changes that organisms want or need.

Natural Selection: Human Evolution.

As we have discussed above, many students have persistent misconceptions regarding how natural selection operates. Our human evolution discussion is particularly effective at eliciting such misconceptions. Andrews et al. (2011b) described in detail how we conduct this discussion, and we will refer the reader to their paper for a full description of the exercise. A brief description of the discussion should be adequate here.

We begin the discussion by asking our students “Are humans still evolving? If so, what trait is changing? Explain why or why not.” Students discussed this question in groups and then presented answers to the class. Many of the answers lacked any reference to the principles of natural selection. For example, students answered “people are getting balder” or “computers are making us smarter.” We then discussed the likelihood of such changes occurring, given the requirements for natural selection (variation, heritability, differential reproductive success).

Sexual Selection: Peacock Trains.

It should not be too difficult for students to understand how natural selection can change the coat color of populations of mice living on sand dunes, but the origin of other traits is harder to understand. For example, Darwin struggled to figure out how natural selection could have created highly ornamental traits, such as the peacock's train, that would seem to reduce an individual's ability to survive. In 1860, he wrote Asa Gray: “the sight of a feather in a peacock's tail … makes me sick!” Darwin eventually proposed elaborate peacock trains could evolve if peahens preferred mating with peacocks that had elaborate trains. Students are likely to experience the same confusion as Darwin, so discussing peacock trains provides an ideal opportunity to reinforce how natural selection works, and to introduce the topic of sexual selection.

We began a discussion of sexual selection by pointing out that natural selection is often summarized as “survival of the fittest” but noted that many animals have traits that seem to decrease their chances of survival. We proposed that the elaborate trains of peacocks are perfect example of such traits; the long feathers would seem to increase the risk of predation. We then asked our students to come up with as many hypotheses as possible to explain why peacocks have such elaborate trains. Students proposed that tail feathers scared away potential predators or helped attract mates. We are not aware of any research on the ability of peacock trains to deter predators, so we told our students that we were going to restrict our discussion to the mating preference hypothesis.

Next, we showed our class a graph from Petrie's famous mate choice study at the Whipsnade Zoo (Figure 3 in Petrie et al. , 1991 ). This graph shows that peacocks with many eyespots (a sign of an elaborate train) garnered more mates than males with fewer eyespots. We also showed students that peahens mated more often with peacocks with bright tail feathers (Figure 3 in Loyau et al. , 2007 ) and mated less often with males that had eye spots removed by researchers (Figure 3 in Petrie and Halliday, 1994 ). These data answer the question of why peacocks have elaborate trains: elaborate trains increase their chances of mating. We explained how such a mating preference could give rise to the elaborate trains using the requirements for natural selection that we used throughout the course (i.e., natural selection requires variation, heritability, and differential reproductive success).

The previous discussion gave rise to a new, interesting question, namely “Why do peahens prefer to mate with peacocks with elaborate trains?” We let our students discuss this for a couple of minutes, solicited answers, discussed possible explanations, and concluded that peacocks with elaborate trains have much better genes than peacocks with less elaborate trains. We introduced this to our students as the “good genes hypothesis” and asked them how they would test it. This was a difficult question for our students. Many students suggested examining peacocks with elaborate trains and testing them to determine whether they were healthier or otherwise superior to peacocks with less elaborate trains. The problem with this experimental design is that both traits (elaborate trains and health) are likely influenced by environmental factors. Peacocks raised in favorable conditions might have elaborate trains and be healthy—and not have good genes. A rigorous test of the good genes hypothesis must test whether peacocks with elaborate trains contribute better genes to offspring than peacocks with less elaborate trains. Petrie (1994) did this by randomly mating peahens and peacocks and showing that the chicks of peacocks with elaborate trains were more likely to survive than the chicks of peacocks with less elaborate trains (see Figure 2 in Petrie, 1994 ). After we completed this discussion, we formally defined sexual selection, talked about why females get to choose, and discussed the consequences of sexual selection.

Evolution of a Complex Trait: Antibiotic Resistance in Escherichia coli.

Students frequently have a hard time understanding how complex traits, such as the vertebrate eye, have evolved through a combination of random mutation and natural selection. Darwin (1859) anticipated this. He wrote in Chapter 6 of the Origin of Species : “To suppose that the eye … could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree.” Darwin then went on to explain how such complex structures could evolve via natural selection through the accumulation of small changes, so long as each small change improved the ability of the organism to survive and reproduce. This is an important concept for students to understand.

We began our discussion of the evolution of complex traits by introducing our students to antibiotic resistance in E. coli . E. coli are rod-shaped bacteria that live in the human digestive tract. Most strains are harmless, but some cause infections that doctors may treat with penicillin or other antibiotics. Some E. coli have a form of the enzyme β-lactamase that can break down the β-lactam ring present in penicillin and other antibiotics, including cefotaxime ( Baquero and Blazquez, 1997 ). The degree to which E. coli are resistant to antibiotics depends on how quickly β-lactamase can break down the β-lactam ring of the antibiotic, and this rate depends on the sequence of amino acids in the β-lactamase enzyme. The β-lactamase allele most commonly present in E. coli populations is the TEM-1 allele, which provides a modest amount of resistance to the antibiotic cefotaxime. In contrast, the TEM-52 allele provides more than 4000 times as much resistance to cefotaxime. TEM-52 differs from TEM-1 by three amino acid substitutions.

Once we introduced our students to this case study, we asked them “What does the mechanism of natural selection predict about the evolution of TEM-1 β-lactamase to TEM-52 β-lactamase?” We let our students discuss this question in pairs, and then randomly called on students for answers. The answer to the question is that TEM-1 must evolve into TEM-52 via three mutations and each mutation must increase the ability of E. coli to survive and reproduce. Our students have not had a difficult time deducing this. Weinreich et al. (2006) synthesized E. coli with each possible combination of amino acids at the three sites that needed to be changed and showed that there were indeed sequences of mutations that could change TEM-1 to TEM-52, while increasing antibiotic resistance in each step. We completed this discussion by telling students that this property of β-lactamase evolution—that each mutation must increase fitness—is a general feature of evolution, and the lecture continued with a discussion of the evolution of the vertebrate eye.

Evolution of Behavior: Apparent Suicide in Lemmings.

A common misconception among students is that natural selection favors traits that are “good for the species.” The lemming suicide myth provides an ideal opportunity to discuss why this is not always true and to show students that the evolutionary origins of altruistic behaviors require special explanation. We began our discussion of lemming suicide by telling students we were going to show them a nature documentary about lemmings, and after the film, they would be asked to answer the question: “Could suicide be an adaptation in lemmings?” Then we showed the class a 3.5-min film clip from the 1958 Walt Disney documentary White Wilderness . The film clip is available on YouTube ( www.youtube.com/watch?v=xMZlr5Gf9yY or search www.Youtube.com for “White Wilderness”). The film appears to show lemmings jumping off cliffs into the Arctic Ocean and swimming to their death. The narrator does not explicitly claim the lemmings are committing suicide, but strongly implies this is what is happening, and most viewers will believe this is what they are watching.

After watching the film, we asked our students “Could suicide be an adaptation in lemmings to prevent overcrowding?” and let them discuss this in small groups. Then we randomly called on students and discussed the answers we obtained. Through discussion, we attempted to explain that natural selection is unlikely to favor suicide, because individuals that commit suicide will not pass on their genes. Gary Larson's Far Side cartoon showing a bunch of lemmings rushing into the water, including one wearing a life preserver, was useful for showing how selfish lemmings who did not commit suicide would pass on their genes and cause the frequency of selfish behavior to increase.

Our students seem to quickly understand why self-destructive behavior is unlikely to evolve via natural selection, but struggled to explain the apparent mass suicide they witnessed in the documentary. For example, some students proposed the lemmings were committing suicide after they had reproduced or because they had a disease they did not want to transmit to their offspring. Others suggested that the lemmings were leaving overcrowded locations in search of a better place to live and reproduce and happened to come across a body of water in their way. These are reasonable suggestions, but turn out to be incorrect. The actual explanation reveals more about human nature than natural selection. According to a documentary aired by the Canadian Broadcasting Company on May 5, 1982 ( www.cbc.ca/fifth/cruelcamera/video2.html ), the dramatic footage in the film White Wilderness of lemmings jumping into the Arctic Ocean was faked. Apparently, the lemmings were pushed off of a cliff into a river. And yet, the film won the 1958 Academy Award for best documentary.

We used two instruments to measure how well students understood natural selection before, during, and after our series of six exercises. The first instrument was a 10-question version of the Conceptual Inventory of Natural Selection (CINS-abbr; Anderson et al. , 2002 ; Fisher, Williams, Lineback, and Anderson, personal communication ; see Table 3 below). This is a multiple-choice test with distracters designed to appeal to students having common misconceptions regarding natural selection and related concepts. In addition, we used seven short essay questions ( Table 2 ) to give students an opportunity to answer evolutionary questions in their own words. The questions we used ( Table 2 ) were variations of questions developed by Bishop and Anderson (1990) for their Open Response Instrument and are similar in form to questions recently described by Nehm et al. (2012) . Each question asked students to explain how an adaptation in a familiar animal might have evolved. Six of the seven questions involved the gain of a trait, and one involved the loss of a trait.

* p -value (calculated from Fisher's exact test) < 0.05.

** p -value < 0.01.

*** p -value < 0.001.

Students were required to complete the CINS-abbr and the short essay questions, but the accuracy of their responses did not affect their grades. Students were told, however, that their responses would be evaluated as part of their course participation grade—which comprised 2% of their grade for the course.

We used the CINS-abbr to measure how much students learned during our entire unit on natural selection. We administered the test twice: in the class period before we began our unit on natural selection and in the class period after we completed the last of our six learning exercises. We calculated the average score on the CINS-abbr before and after instruction and used this to calculate the normalized gain ( Hake, 1998 ) for the class. We did this in 2011 and 2012. We tested the statistical significance of increases in test scores using a nonparametric sign test. Scores from students who did not take both the pre- and postinstruction tests were not included in the analysis.

We used seven short essay questions ( Table 2 ) to assess learning in two ways. First, we used the essay questions as an alternative to the CINS-abbr to measure how much students learned in the entire unit on natural selection. Second, we used these essay questions to monitor learning throughout our six-lecture unit on natural selection.

We administered the essay questions before, during, and after our unit on natural selection as follows. Each student answered one short essay question before we began our unit on natural selection and then one question after each of the six classroom exercises. We were concerned the questions might vary in difficulty, so we randomly divided our class into seven groups and gave each group a different question each day we tested the class. Group one answered question one on the first day (before instruction), question two on the second day, and so on, answering question seven after the last of the learning exercises. Group two answered question two on the first day, question three on the second day, and question one after instruction was over, and so on. With this design, each student answered a different question each day, but the class as a whole always answered the same set of questions. This allowed us to compare the average score of the class on different days. Administering these short essay questions took a substantial amount of class time, so we did this only in 2011.

We graded all of the short essay questions using the rubric of Andrews et al. (2011b) . This rubric evaluated student responses according to how well they addressed the three key concepts we emphasized in lecture: variation for a trait within a population, heritability of the trait, and differential reproductive success. We did not discuss the questions or student answers to the questions during class, and we did not read any of the student answers until after the course was over. We scored student responses in a random order with the name of the student and the date obscured. All of the responses were independently scored by two of the authors (S.T.K. and T.M.A.), and any differences in scores were resolved through discussion.

We used the short essay data and an analysis of variance (ANOVA) to estimate how much students learned during the first lesson. To do this, we compared the average test score collected before instruction (PRE) with the average score after the first lesson (dog breeding), using ANOVA. We explicitly paired scores for each individual student and accounted for potential differences in difficulty among the various questions administered. We also evaluated an interaction term (i.e., = difference between PRE and the first lesson × essay question) to determine whether the degree of initial learning gains differed based on the essay question assigned; we removed the interaction if it was not statistically significant.

Next, we were interested in determining whether and the degree to which student scores on the essay questions increased throughout our unit. In this second analysis, we analyzed only the data collected after the first lesson (dog breeding) and used a linear regression to quantify the degree of learning gain. We did not include the test scores collected before instruction (PRE), because we wanted to see whether students benefited from continued instruction (i.e., represented by a nonzero and increasing slope of the line) or whether the gains after initial instruction (which should be highest) were minimal (i.e., represented by a flat line). We analyzed these data with a generalized linear mixed model that allowed us to account for repeated observations from the same students by including a compound symmetric covariance structure ( Littell et al. , 2006 ). We also accounted for potential differences in difficulty among the various questions administered. Additionally, we evaluated an interaction term (i.e., = lesson × essay question) to determine whether changes in the average score over the series of exercises in the unit differed based on the essay question assigned; we removed the interaction if it was not statistically significant.

We also used surveys to assess student attitudes toward the six learning activities (see Table 4 below). Participation in these surveys was voluntary and anonymous.

a Student responses were coded on a scale from 1 to 6: 1 = strongly disagree, 2 = disagree, 3 = slightly disagree, 4 = slightly agree, 5 = agree, 6 = strongly agree. Surveys were conducted on the same day each learning exercise was performed. Survey data for the Peacock exercise were not collected, due to a lack to time on the day the exercise was taught.

Data from the CINS-abbr showed that, before instruction, many students appeared to have misconceptions regarding natural selection ( Table 3 ). Between 25 and 50% of our class seemed to believe evolution was caused by the environment changing individuals or species evolving out of need ( Table 3 ). As we discussed in the Introduction , these are common misconceptions among introductory biology students.

Our class showed impressive learning gains on the 10-question version of the CINS both years we administered this test ( Figure 1 ). In 2011, pre- and postinstruction CINS-abbr scores were available for 32 of the 41 students in the course. Before instruction, the class average on the CINS-abbr was 6 (out of 10; σ = 2.55). After instruction, the average was 8.88 (σ = 1.45). This corresponds to a normalized gain of 0.72. Analysis of student responses on specific questions suggested the frequency of specific misconceptions declined after instruction ( Table 3 ). In particular, fewer students seemed to have the misconception that evolution happens because the environment changes individuals.

Figure 1. Pre- and postinstruction test scores on the CINS-abbr in 2011 and 2012.

We observed similar learning gains on the CINS-abbr in 2012. In 2012, pre- and postinstruction CINS-abbr scores were available for 42 of the 47 students in the courses. The average score among these students increased from 7.14 (σ = 2.55) to 9.24 (σ = 1.03) which corresponds to a normalized gain of 0.73. As we discuss below, these are exceptionally large learning gains for this test. Notice also that the normalized gain was essentially the same both years (0.72 vs. 0.73), despite the fact the natural selection unit was taught by two different instructors and that the composition of the student body was substantially different in 2011 and 2012.

We administered the short essay questions seven times to our class of 41 students in 2011 and received 236 student responses. This corresponds to a response rate of 236/(41 × 7) = 82%. As indicated above, all questions were graded by two researchers; the correlation between scores was initially 0.82 (all differences resolved via discussion) Seven student responses were culled before we began statistical analysis. Six students missed three lectures in a row, and we dropped the responses of these students after these absences. This removed six responses from our data. We also dropped one student's response to the final question. It was the only response on the last two testing dates that received a score of zero. The response was unusually short, and the student had earned full credit on two previous questions. Furthermore, this response was identified as an outlier in a general linear model. After dropping these seven responses, we had a final data set of 229 responses, or a response rate of 80%.

Student responses on the short essay questions showed substantial learning gains. Before instruction, the most common score in the class was 0 points (out of 6) and the average score in the class was 2.84. After instruction, the most common score in the class was 6 points, and the average score was 4.90. This corresponds to a normalized gain of 0.65, which, as we discuss below, compares favorably with results from other courses for similar questions.

On the basis of our analysis of student responses to the short essay questions, we quantified a large increase in understanding after the first learning exercise (i.e., difference between PRE and the Dog lesson, Figure 2a ). Average scores increased by 1.23 points (95% CI = 0.48–1.98) after the first learning exercise ( F (1, 30) = 11.18, p = 0.002; difference between PRE and Dog lesson in Figure 2 ).

Figure 2. Average scores on the short essay questions before instruction (PRE) and after each lesson (Dogs, Mice, etc.) in 2011. (a) The average score in the class; (b) the average score for each component of the total score included in the rubric. We analyzed the data in (a) in two ways. First, we quantified the initial learning gains after one lesson (difference between PRE and Dogs). Next, we determined whether learning gains continued to occur after initial instruction; the line in (a) shows the predicted increase in the average score for the class throughout the set of exercises. Test scores before instruction (PRE) were not included in this second analysis.

We also observed that student scores continued to improve throughout the series of our exercises by an average of 0.15 points (95% CI = 0.05–0.25) with each additional exercise ( F (1, 145) = 9.02, p = 0.003; the Dog lesson through the Lemmings lesson on Figure 2a ), which amounts to an average total increase of 0.75 points (95% CI = 0.25–1.25) over the series of five exercises. We found little evidence that the direction or magnitude of these increases differed based on which essay question students were assigned (i.e., interactive effect = lesson × essay question, initial increase: F (6, 24) = 0.61, p = 0.72; subsequent increase: F (6, 139) = 1.1, p = 0.37).

Our rubric for the short essay questions contained three components: variation, heritability, and differential reproductive success. Student answers consistently received the fewest points for the heritability component ( Figure 2b ). This component also seemed to be the most difficult for students to learn. Students’ scores for variation and differential reproductive success quickly rose after the first lesson, and then changed relatively little (especially for the concept of variation). In contrast, scores for the heritability component of student answers steadily increased throughout instruction. This increase was responsible for 77% of the increase in scores after lesson 1.

The survey of student attitudes regarding the six natural selection exercises showed that students generally viewed these lessons positively ( Table 4 ). On average, the class agreed the exercises were interesting, challenging, understandable, and valuable learning experiences. None of the exercises received remarkably low or high evaluations, but the lemming discussion (which was the last one taught) did seem to stand out as being viewed as particularly interesting and challenging.

We developed and assessed six classroom activities for teaching natural selection to introductory biology students. All our assessments suggested the activities were both engaging and effective.

The learning gains we observed on the 10-question version of the CINS compare very favorably with results from other classrooms. Andrews et al. (2011b) administered the same 10-question CINS-abbr to 33 introductory biology courses randomly sampled from major universities across the United States. Students in these classes took the CINS-abbr before and after instruction on natural selection. The average normalized gain among these courses was 0.26, and the highest normalized gain observed was 0.68 (T.M.A., unpublished data). In our classroom, we observed a normalized gain of 0.72 when S.T.K. taught the course and 0.73 when PhD student taught the lessons. Notice that our learning gains were higher than in any of the other classrooms studied by Andrews et al. , even when our unit on natural selection was taught by a graduate student with very little teaching experience. We interpret this as evidence that the lessons we describe here are effective for promoting learning.

Results from assessment using short essay questions also compare favorably with results from other institutions. The normalized gain associated with our six learning activities, as measured by our short essay questions, was 0.65. The average normalized gain for a short essay question in the national study of Andrews et al. (2011b) was 0.06, approximately one-tenth of what we observed in our classroom. This is additional evidence that our learning exercises were effective. There is, however, a methodological difference to note between our assessment and that in the survey of Andrews et al. (2011b) . We used seven short essay questions. Andrews et al. (2011b) used only one question: a question on cheetahs very similar to our cheetah question ( Table 2 ). The data, therefore, are not perfectly comparable. However, there is no reason to suspect our set of questions was easier than the cheetah question used by Andrews et al. (2011b) . We observed a standardized gain of 0.88 for the cheetah question in our classroom; the standardized gains for all of the other questions were lower . Therefore, the set of questions we used to assess our learning exercises was probably harder than the question used by Andrews et al. (2011b) .

Recent research ( Nehm and Ha, 2010 ; Nehm et al. , 2012 ) has shown the ability of students to answer questions regarding natural selection depends on the context of the question. In particular, Nehm and Ha (2010) showed that questions that involve trait loss, unfamiliar species, or evolution between species are more difficult for students to answer. Had this research been available when we started our project, we would have broadened the scope of the short-answer questions in our assessment. However, we did include one question relating to trait loss (in whales), and this provides us with some insight for how effective our learning exercises might be for allowing students to reason about natural selection in contexts beyond evolution of a new trait within a species. As expected from Nehm and Ha's (2010) results, scores on our trait-loss question were, on average, lower than the six trait-gain questions. However, the learning gains observed with the trait-loss whale questions did not appear to be lower than those of the other questions. We calculated the normalized gain for each of the seven questions, and the normalized gain for the whale evolution question was 0.60. This was equal to the median of the normalized gain among our seven questions. We never discussed or mentioned trait loss at any time during the course, so it seems likely that our students learned natural selection well enough that they were able to reason effectively about the relatively novel evolutionary scenario of how traits are lost.

Our pre- and postinstruction testing has shown that our students made impressive progress understanding one of the most difficult concepts in biology. We attribute these learning gains to our classroom exercises and suggest four characteristics of our lessons may have been important for promoting learning. First, we designed these lessons to specifically target student misconceptions. We did not just use active learning—we used specific methods in an active-learning format to help students move past misconceptions. Second, we explicitly discussed the genetic basis of evolution. Many student misconceptions regarding natural selection relate to genetics, so making a connection to students’ prior genetics knowledge should be helpful. Third, we presented students with multiple examples of selection at work in a variety of different contexts. Finally, we did our best to create exercises that engaged our students as deeply as possible ( Table 4 ).

We have attributed the dramatic increase in test scores we observed with our students to the classroom activities we conducted, and have proposed four reasons why our lessons may have been effective. We do acknowledge, however, the design of our study makes it impossible to unambiguously attribute student learning to any specific element of our instruction. We conducted six classroom activities during our unit on natural selection, but these activities were not the only opportunities students had to learn. Students were assigned textbook readings before each lesson, and this may have contributed to some of their learning. Similarly, most of our lectures included a fair amount of ordinary lecturing, and this could have contributed to student learning. There are many other possibilities. However, it is not credible to us that any of these aspects of our course were unique enough to explain the uniquely high learning gains we observed.

Readers may wonder whether any of our six lessons were more or less effective than others. For example, the average class score on the short essay questions dropped after the mice and peacock discussions, which raises the question of whether these lessons were effective or not. Unfortunately, our study was not designed to measure how much students learned in a specific activity. There are several reasons why not. First, we did not perform pre- and postinstruction testing for any of the individual learning activities. We administered the CINS-abbr before and after our unit on natural selection and administered essay questions to the class before, after, and during our unit on natural selection, but we did not perform any assessment immediately before and/or immediately after any of the activities described here. Second, our course had only 41 students, and they answered a single essay question each day we did testing during the unit. This does not give us a lot of statistical power to measure how much students learned from one lesson to the next. Third, student understanding can temporarily “dip” after a lesson, especially if a lesson presents students with a principle in a new context. When instructors do this, students need to restructure their knowledge to deal with the new context (e.g., Bransford and Schwartz, 1999 ; Barnett and Ceci, 2002 ; Lobato, 2008 ). Fourth, it is important to remember that the essay questions provide only one measure of how well students understand natural selection. Learning gains might have looked different had we used other questions. Finally, we emphasize that our data describes learning gains for the sequence of exercises as we taught them. The apparent effectiveness of any lesson almost certainly strongly depends on what is taught before it. For example, the dog-breeding lesson was associated with higher learning gains than the discussion of beach mice. If we used the mice lesson first and followed it up with a discussion of dog breeding, we might observe the opposite.

Instructors considering incorporating our learning exercises into their courses may wish to modify them to suit the specific needs of their courses. If this is done, instructors must ensure these activities give students the opportunity to personally construct an understanding of natural selection. In particular, we strongly encourage instructors to make sure that students: 1) formulate an initial answer to each question on their own, 2) discuss their answers with a few other students, 3) participate in a discussion with the entire class, and 4) recognize how these activities relate to the main concepts taught in a course. All of this takes time but is important for learning. There is accumulating evidence that instructors attempting to use active-learning methods do not include these elements in their instruction, and therefore fail to see the learning gains they hope to achieve ( Turpen and Finkelstein, 2009 ; Andrews et al. , 2011b ; Ebert-May et al. , 2011 ).

Instructors using the exercises described in this paper in their classroom should make an effort to assess whether their students are learning natural selection. Some sort of pre- and postinstruction testing is necessary to do this. The CINS-abbr ( Anderson et al. , 2002 ), ACORNS (Assessing Contextual Reasoning about Natural Selection) ( Nehm et al. , 2012 ), or open-response questions (described by Bishop and Anderson, 1990) are reasonable instruments to use. There are no established criteria for what constitutes acceptable learning gains on these tests, but a normalized gain of ≥0.50 probably represents a substantial achievement.

In the course we taught, we devoted six 50-min lectures to teaching natural selection. This might seem excessive. Two lines of evidence suggest this time was well spent. First, after five lectures on natural selection, many of our students were unable to recognize that suicide was an unlikely adaptation. This implies their understanding of natural selection was still developing or they were unable to draw upon their knowledge when that knowledge was relevant. Second, the average test score on the short essay questions we used to assess understanding of natural selection did not appear to level off. Student answers appeared to be still improving at the end of our series of exercises ( Figure 2 ). In particular, students’ understanding of the genetic basis of evolution seemed to be improving ( Figure 2 ).

We will conclude this paper with a few comments on a controversial aspect of moving from traditional lectures to active learning. Most of the learning exercises described here require a fair amount of time to conduct. This is especially true for the discussions of dog breeding, human evolution, and peacock trains. An instructor using these activities for the first time may find he or she has less time to cover other material. This could be viewed as a reason not to use active learning—especially if instructors feel pressure to cover as much material as possible. We have two responses. First, the goal of teaching is not to cover as much as possible, but to teach as much as possible, and a large body of evidence shows that students learn more in courses that make extensive use of active learning (e.g., Hake, 1998 ; Knight and Wood, 2005 ; Freeman et al. , 2007 ). Second, natural selection is one of the most important concepts in biology, but it is difficult for students to learn. All evidence suggests many students need specialized and time-consuming instruction to learn natural selection well enough to avoid falling back upon glaringly inaccurate misconceptions. Instructors might cover more if they used traditional lectures to cover natural selection, but it is hard to imagine what other topics students might learn that would make up for not understanding the principle cause of evolution.

ACKNOWLEDGMENTS

We thank the National Science Foundation for funding (CCLI 0942109) and our students for helping us develop these learning exercises. We thank two anonymous reviewers for thoughtful comments that improved the manuscript.

• Abrams E, Southerland S ( 2010 ). The hows and whys of biological change: how learners neglect physical mechanisms in their search for meaning . Int J Sci Educ 23 , 1271-1281. Google Scholar
• Anderson DL, Fisher KM, Norman GJ ( 2002 ). Development and evaluation of the conceptual inventory of natural science . J Res Sci Teach 39 , 952-978. Google Scholar
• Andrews TM, Kalinowski ST, Leonard MJ ( 2011a ). “Are humans evolving?” A classroom discussion to change student misconceptions regarding natural selection . Evol Educ Outreach 4 , 456-466. Google Scholar
• Andrews TM, Leonard MJ, Colgrove CA, Kalinowski ST ( 2011b ). Active learning not associated with student learning in a random sample of college biology courses . CBE Life Sci Educ 10 , 394-405. Link ,  Google Scholar
• Baquero F, Blazquez J ( 1997 ). Evolution of antibiotic resistance . Trends Ecol Evol 12 , 482-487. Medline ,  Google Scholar
• Barnett SM, Ceci SJ ( 2002 ). When and where do we apply what we learn?: A taxonomy for far transfer . Psychol Bull 128 , 612-637. Medline ,  Google Scholar
• Bishop B, Anderson C ( 1990 ). Student conceptions of natural selection and its role in evolution . J Res Sci Teach 27 , 415-427. Google Scholar
• Bransford JD, Brown AL, Cocking RR (eds.) ( 2000 ). How People Learn: Brain, Mind, Experience, and School In: Washington, DC: National Academies Press. Google Scholar
• Bransford JD, Schwartz D ( 1999 , Ed. A Iran-NejadPD Pearson , Rethinking transfer: a simple proposal with multiple implications In: Review of Research in Education, vol. 24 , Washington, DC: American Educational Research Association, 61-100. Google Scholar
• Brumby MN ( 1984 ). Misconceptions about the concept of natural selection by medical biology students . Sci Educ 68 , 493-503. Google Scholar
• Catrambone R, Holyoak KJ ( 1989 ). Overcoming contextual limitations on problem-solving transfer . J Exp Psychol 15 , 1147-1156. Google Scholar
• Coyne J ( 2009 ). Why Evolution Is True , New York: Viking. Google Scholar
• Darwin C ( 1859 ). On the Origin of Species, London: John Murray . Google Scholar
• diSessa AA ( 2006 , Ed. RK Sawyer , A history of conceptual change research: threads and fault lines In: The Cambridge Handbook of the Learning Sciences , New York: Cambridge University Press, 265-281. Google Scholar
• Dobzhansky T ( 1973 ). Nothing in biology makes sense except in the light of evolution . Am Biol Teach 35 , 125-12. Google Scholar
• Duit R, Treagust DF ( 2003 ). Conceptual change: A powerful framework for improving science teaching and learning . Int J Sci Educ 25 , 671-688. Google Scholar
• Fisher K, Williams KS, Lineback JE, Anderson D (in prep.). Conceptual Inventory of Natural Selection—Abbreviated (CINS-abbr) . Google Scholar
• Ebert-May D, Derting TL, Hodder J, Momsen JL, Long TM, Jardeleza SE ( 2011 ). What we say is not what we do: effective evaluation of faculty professional development programs . Bioscience 61 , 550-558. Google Scholar
• Freeman S, et al. ( 2007 ). Prescribed active learning increases performance in introductory biology . CBE Life Sci Educ 6 , 132-139. Link ,  Google Scholar
• Gregory TR ( 2009 ). Understanding natural selection: essential concepts and common misconceptions . Evol Educ Outreach 2 , 156-175. Google Scholar
• Haak DC, HilleRisLambers J, Pitre E, Freeman S ( 2011 ). Increased structure and active learning reduce the achievement gap in introductory biology . Science 332 , 1213-1216. Medline ,  Google Scholar
• Hake RR ( 1998 ). Interactive-engagement versus traditional methods: a six-thousand-student survey of mechanics test data for introductory physics courses . Am J Phys 66 , 64-74. Google Scholar
• Hammer D ( 1996 ). Misconceptions or P-Prims: how may alternative perspectives of cognition structure influence instructional perceptions and intentions? . J Learn Sci 5 , 97-127. Google Scholar
• Hewson PW, Beeth ME, Thorley NR ( 1998 , Ed. BJ FraserKG Tobin , Teaching for conceptual change In: International Handbook of Science Education , London: Kluwer Academic, 199-218. Google Scholar
• Hoekstra HE, Hirschmann RJ, Bundey RA, Insel PA, Crossland JP ( 2006 ). A single amino acid mutation contributes to adaptive beach mouse color pattern . Science 313 , 101-104. Medline ,  Google Scholar
• Kalinowski ST, Leonard MJ, Andrews TM ( 2010 ). Nothing in evolution makes sense except in the light of DNA . CBE Life Sci Educ 9 , 87-97. Link ,  Google Scholar
• Kaufman DW ( 1974 ). Adaptive coloration in Peromyscus polionotus : experimental selection by owls . J Mammol 55 , 271-283. Google Scholar
• Knight JK, Wood WB ( 2005 ). Teaching more by lecturing less . Cell Biol Educ 4 , 298-310. Link ,  Google Scholar
• Lamarck J ( 1809 ). Philosophie Zoologique. Paris In: Translated by H Elliot as Zoological Philosophy , London: Macmillan, 1914; reprinted by University of Chicago Press, 1984. Google Scholar
• Littell RC, Milliken GA, Stroup WW, Wolfinger RD, Schabenberger O ( 2006 ). SAS for Mixed Models , 2nd ed. Cary, NC: SAS Institute. Google Scholar
• Lobato J ( 2008 , Ed. AE KellyRA LeshJY Baek , Research methods for alternative approaches to transfer: implications for design experiments In: Handbook of Design Research Methods in Education , New York: Routledge, 167-194. Google Scholar
• Loyau A, Gomez D, Moureau B, Thery M, Hart NS, Saint Jalme M, Bennett ATD, Sorci G ( 2007 ). Iridescent structurally based coloration of eyespots correlates with mating success in the peacock . Behav Ecol 18 , 1123-1131. Google Scholar
• Marton F ( 2006 ). Sameness and difference in transfer . J Learn Sci 15 , 499-535. Google Scholar
• Mason L (ed.) ( 2007 ). Bridging the cognitive and sociocultural approaches in research on conceptual change . Educ Psychol 42 (special issue). Google Scholar
• Mestre J ( 2003 ). Transfer of Learning: Issues and Research Agenda: Report of a Workshop Held at the National Science Foundation . www.nsf.gov/pubs/2003/nsf03212/nsf03212.pdf (accessed 17 July 2013). Google Scholar
• Miller JD, Scott EC, Okamoto S ( 2006 ). Public acceptance of evolution . Science 313 , 765-766. Medline ,  Google Scholar
• Murphy PK, Mason L ( 2006 , Ed. PA AlexanderPH Winne , Changing knowledge and beliefs In: Handbook of Educational Psychology , 2nd ed. Mahwah, NJ: Lawrence Erlbaum, 305-324. Google Scholar
• Nehm RH, Beggrow EP, Opfer JE, Ha M ( 2012 ). Reasoning about natural Selection: diagnosing contextual competency using the ACORNS instrument . Am Biol Teacher 74 , 92-98. Google Scholar
• Nehm RH, Ha M ( 2010 ). Item feature effects in evolution assessment . J Res Sci Teach 48 , 237-256. Google Scholar
• Nehm RH, Reilly L ( 2007 ). Biology majors’ knowledge and misconceptions of natural selection . Bioscience 57 , 263-272. Google Scholar
• Nehm RH, Schonfeld I ( 2008 ). Measuring knowledge of natural selection: a comparison of the CINS, and open-response instrument, and oral interview . J Res Sci Teach 45 , 1131-1160. Google Scholar
• Petrie M ( 1994 ). Improved growth and survival of peacocks with more elaborate trains . Nature 3 , 598-599. Google Scholar
• Petrie M, Halliday T ( 1994 ). Experimental and natural changes in the peacock's ( Pavo cristatus ) train can affect mating success . Behav Ecol Sociobiol 35 , 213-221. Google Scholar
• Petrie M, Halliday T, Sanders C ( 1991 ). Peahens prefer peacocks with elaborate trains . Anim Behav 41 , 323-331. Google Scholar
• Scott PH, Asoko HM, Driver RH ( 1991 , Ed. R DuitF GoldbergH Niedderer , Teaching for conceptual change: a review of strategies In: Research in Physics Learning: Theoretical Issues and Empirical Studies , Kiel, Germany: IPN, 310-329. Google Scholar
• Sinatra GM, Brem SK, Evans EM ( 2008 ). Changing minds? Implications of conceptual change for teaching and learning about biological evolution . Evol Educ Outreach 1 , 189-195. Google Scholar
• Sutter NB, et al. ( 2007 ). A single IGF1 allele is a major determinant of small size in dogs . Science 316 , 112-115. Medline ,  Google Scholar
• Tanner K, Allen D ( 2005 ). Approaches to biology teaching and learning: understanding the wrong answers—teaching toward conceptual change . Cell Biol Educ 4 , 112-117. Link ,  Google Scholar
• Turpen C, Finkelstein ND ( 2009 ). Not all interactive engagement is the same: variations in physics professors’ implementation of peer instruction . Phys Rev Spec Top Phys Educ Res 5 , 020101. Google Scholar
• Vosniadou S ( 2008 ). International Handbook of Research on Conceptual Change , New York: Routledge. Google Scholar
• Weinreich DM, Delaney NF, DePristo MA, Hartl DL ( 2006 ). Darwinian evolution can follow only very few mutation paths to fitter proteins . Science 312 , 111-114. Medline ,  Google Scholar
• Thirty years of conceptual change research in biology – A review and meta-analysis of intervention studies 1 Nov 2023 | Educational Research Review, Vol. 41
• Avoid an Allele Audit 1 Jan 2023 | The American Biology Teacher, Vol. 85, No. 1
• Genie: an interactive real-time simulation for teaching genetic drift 21 February 2022 | Evolution: Education and Outreach, Vol. 15, No. 1
• Patricia Jaimes ,
• Julie C. Libarkin , and
• Dominik Conrad
• Ross Nehm, Monitoring Editor
• A Hands-On Set for Understanding DNA Replication, Transcription & Polymerase Chain Reaction (PCR) 1 Jan 2020 | The American Biology Teacher, Vol. 82, No. 1
• Evolutionary Content Knowledge, Religiosity and Educational Background of Slovene Preschool and Primary School Pre-Service Teachers 1 Jan 2020 | Eurasia Journal of Mathematics, Science and Technology Education, Vol. 16, No. 7
• Examining Reasoning Practices and Epistemic Actions to Explore Students’ Understanding of Genetics and Evolution 9 November 2019 | Science & Education, Vol. 28, No. 9-10
• Concept inventories as a resource for teaching evolution 16 January 2019 | Evolution: Education and Outreach, Vol. 12, No. 1
• Tarsier Goggles: a virtual reality tool for experiencing the optics of a dark-adapted primate visual system 6 March 2019 | Evolution: Education and Outreach, Vol. 12, No. 1
• Pancake Evolution: A Novel & Engaging Illustration of Natural Selection 1 Feb 2019 | The American Biology Teacher, Vol. 81, No. 2
• Developing a Cross-Curricular Session about Evolution for Initial Teacher Education: Findings from a Small-Scale Study with Pre-service Primary School Teacher 17 July 2019
• Iterative design of a simulation-based module for teaching evolution by natural selection 26 April 2018 | Evolution: Education and Outreach, Vol. 11, No. 1
• Surveying University Students’ Recognition of “Preservation of Species and Race” 30 Nov 2018 | Journal of Research in Science Education, Vol. 59, No. 2
• The genetic basis of size in pet dogs: The study of quantitative genetic variation in an undergraduate laboratory practical 5 November 2018 | Biochemistry and Molecular Biology Education, Vol. 46, No. 6
• Dissecting chicken wings in an introductory geology course to help students discover evidence—hiding in plain sight—of dinosaur–bird evolution 29 October 2018 | Journal of Geoscience Education, Vol. 66, No. 4
• M. A. Ziadie and
• T. C. Andrews
• Kathryn E. Perez, Monitoring Editor
• Bacterial Survivor: An Interactive Game that Combats Misconceptions about Antibiotic Resistance 1 Jan 2018 | Journal of Microbiology & Biology Education, Vol. 19, No. 3
• Testing the effectiveness of two natural selection simulations in the context of a large-enrollment undergraduate laboratory class 14 July 2017 | Evolution: Education and Outreach, Vol. 10, No. 1
• Steven T. Kalinowski ,
• Mary J. Leonard , and
• Mark L. Taper
• Melissa L. Aikens ,
• Lisa A. Corwin ,
• Tessa C. Andrews ,
• Brian A. Couch ,
• Sarah L. Eddy ,
• Lisa McDonnell , and
• Gloriana Trujillo
• Diane K. O'Dowd, Monitoring Editor
• Effects of the Biology Inquiry Field - Trip Program on Elementary Pre - service Teachers’ Evolution Related Concept, and Perception and Endangered Species Conservation related Knowledge, Awareness and Attitude – A Quantitative Research - 1 Sep 2016 | BIOLOGY EDUCATION, Vol. 44, No. 3
• Getting Wrinkly Spreaders to demonstrate evolution in schools 1 Jun 2014 | Trends in Microbiology, Vol. 22, No. 6

Submitted: 12 June 2012 Revised: 25 January 2013 Accepted: 26 January 2013

© 2013 S. T. Kalinowski et al. CBE—Life Sciences Education © 2013 The American Society for Cell Biology. This article is distributed by The American Society for Cell Biology under license from the author(s). It is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings

Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now .

• Advanced Search
• Journal List

Natural selection according to Darwin: cause or effect?

Ben bradley.

School of Psychology, Charles Sturt University, 164 George Street, Bathurst, NSW 2795 Australia

In the 1940s, the ‘modern synthesis’ (MS) of Darwinism and genetics cast genetic mutation and recombination as the source of variability from which environmental events naturally select the fittest, such ‘natural selection’ constituting the cause of evolution. Recent biology increasingly challenges this view by casting genes as followers and awarding the leading role in the genesis of adaptations to the agency and plasticity of developing phenotypes—making natural selection a consequence of other causal processes. Both views of natural selection claim to capture the core of Darwin’s arguments in On the Origin of Species . Today, historians largely concur with the MS’s reading of Origin as a book aimed to prove natural selection the cause ( vera causa ) of adaptive change. This paper finds the evidence for that conclusion wanting. I undertake to examine the context and meaning of all Darwin’s known uses of the phrase vera causa , documenting in particular Darwin’s resistance to the pressure to prove natural selection a vera causa in letters written early in 1860 . His resistance underlines the logical dependence of natural selection, an unobservable phenomenon, on the causal processes producing the observable events captured by the laws of inheritance, variation, and the struggle for existence, established in Chapters 1–3 of Origin .

Since the synthesis of Darwinism and Mendelian genetics in the 1930s and 1940s, Darwinians have not regarded the struggle for existence as a cause of natural selection. (Radick, 2009 , p. 162). They admit variation as a  vera causa  in one case, they arbitrarily reject it in another, without assigning any distinction in the two cases. The day will come when this will be given as a curious illustration of the blindness of preconceived opinion. (Darwin, 1859a , p. 423).

Introduction

Before the seminal marriage of evolutionary theory with modern genetics, Gregor Mendel was commonly thought non-Darwinian—because the effects of genetic mutations were held to be discontinuous, and so incompatible with Darwin’s evolutionary dictum that ‘nature does not make jumps’ (e.g. Bateson, 1909 ; cf. Darwin, 1859a , pp. 171ff: ‘natura non facit saltum’). As soon as the ‘modern synthesis’ (MS; Huxley, 1942 ) gained influence over evolutionary science, its deployment of population genetics meant Mendel was recast as a Darwinian (Fisher, 1936 ; Sapp, 1990 ).

Like transformations have moulded understandings of Charles Darwin’s own work. Before the 1930s, his writings had played divers roles across different branches of science: biology; genetics; geology; biometrics; and taxonomy amongst them (e.g. Depew & Weber, 1994 ; Gayon, 1992 ). Come the MS, however, and Darwin got recast as the purveyor of a single idea—‘the best idea anyone has ever had’—meaning that, by century’s end, Darwinism had become synonymous with a belief in natural selection which was, purportedly, ‘the fundamental mechanism responsible’ for evolution (e.g. Dennett, 1995 , pp. 21, 46). As a result, Darwin’s many other observations and theses about how evolution worked were side-lined as wrong or irrelevant to contemporary science. At the same time, the MS endowed Darwin’s treatment of natural selection with a newly-narrowed, and still-dominant identity (Provine, 1988 ; Smocovitis, 1992 ). It became the cause or mechanism of evolution: chance environmental events blindly winnowing random genetically-caused variations in organisms’ DNA, so that descendant gene pools (and, only consequently , organisms) grow better adapted to their conditions of life than were their ancestor populations.

Syncing nicely with the MS, by the year 2000 historians of science had firmly established an MS-consistent reading of On the Origin of Species (Darwin, 1859a ; henceforth ‘ Origin ’) as a book primarily aimed to prove that ‘natural selection’ is the causal mechanism of evolution (e.g. Hodge, 2013 ; Hull, 2003 ; Pence, 2018 ; Ruse, 2005 ; Waters, 2003 ). Yet, over recent decades, biology’s MS has increasingly been challenged, qualified, or ‘extended’ by the findings of evolutionary science (e.g. Laland et al., 2015 ; Oyama et al., 2001 ; Walsh, 2015 ; West-Eberhard, 2003 ). In the process, scientists’ views have begun to diverge about the central thesis of Origin and, in particular, about how Darwin understood ‘natural selection.’ Such divergence presents a challenge to historians’ readings of Origin as purveying a view of evolution consonant with the MS. Does Darwin’s masterwork genuinely—but wrongly, according to a growing number of twenty-first century evolutionary biologists—equate natural selection to a ‘mindless, purposeless, mechanical process,’ as both modern synthesisers and their critics continue to claim (e.g. Dennett, 1995 , p. 34; Lewontin, 1983 , p. 275; Pigliucci et al., 2010 , p. 11)? In which case evolutionary biology is en route to becoming non -Darwinian. Or do historians’ MS-consistent readings of Origin miscast its arguments?

This essay tackles those questions. It aims to reassess historical evidence about Darwin’s take on the argument that natural selection provides the causal mechanism for evolutionary change. I will examine in detail: how Darwin himself used the phrase ‘ vera causa ’; the way Origin constructs its argument about the causes of evolution; and how Darwin defended that book against criticisms of his approach to scientific investigation. I also review the grounds for modern historiographic conclusions that Origin argues natural selection to be a causal mechanism. In this, I draw out conflicting uses of that ambiguous phrase ‘ verae causae ’ by Darwin scholars. I conclude by showing that understanding natural selection as an effect of other processes—not a cause in its own right—has critical significance for contemporary evolutionary theory. To that end, I will start my argument by briefly outlining the place of understandings of Darwin’s work in debates about the explanatory status of natural selection in today’s evolutionary science.

The contemporary scientific debate about natural selection

Twenty-first century science poses three kinds of challenge to MS understandings of evolution, under the banners: ‘evo-devo’; ‘developmental systems theory’ (DST); and a phenotype-first theory of adaptive change as led by ‘developmental plasticity.’ Despite their considerable differences (Bradley, 2020 , pp. 97–101), these new approaches have together been dubbed the ‘extended evolutionary synthesis.’ But they do not all challenge the idea of natural selection as cause (e.g. Laland et al., 2013 ; Pigliucci et al., 2010 ). A subset of these approaches, which do consistently challenge the causal interpretation of natural selection, have been dubbed, ‘developmental,’ ‘situated’ and ‘active’ Darwinism’ (Noble, 2020 ; Walsh, 2012 , 2015 ).

Evolutionary developmental biology (‘evo-devo’) addresses ‘the profound neglect of development in the standard modern synthesis framework of evolutionary theory’ (Muller, 2007 , p. 943). It seeks to understand both how developmental processes have evolved and how they may have helped cause the evolution of adaptations (Arthur, 2002 ). But evo-devo typically retains what its advocates call ‘Darwin’s’ conception of natural selection: as a causal ‘process’ or ‘mechanism’ which ‘acts’ at the population level (e.g. Arthur, 2002 , pp. 759–762; cf. Hall, 2012 , p. 187; Muller, 2007 , p. 94). DST typically theorizes phenotypic adaptation as developed via a system which incorporates an organism’s or population’s genes along with their ‘environments’—the term ‘environments’ including the ‘internal’ intra-cellular environment’s control of gene expression (epigenetics), plus developmental processes, alongside stable features of the ‘external’ environment (Oyama et al., 2001 , pp. 1–11). However, DST still confusingly casts natural selection both as an ‘emergent phenomenon’ (a higher-order effect?) stemming from ‘lower-level’ processes, and as a productive cause of adaptation (Griffiths & Gray, 2001 , p. 214; Weber & Depew, 2001 , pp. 244–249). Finally, West-Eberhard ( 2003 , pp. 33ff; Walsh, 2010 ) has advanced a comprehensive, evolutionary theory of the phenotype which conceptualises phenotypic development in terms of ‘plasticity’: the ability of an organism to react to an internal or external environmental input with reversible or irreversible changes ‘in form, state, movement, or rate of activity.’ West-Eberhard’s understanding of plasticity incorporates a stress on the agency of whole organisms, a theme that has become increasingly prominent over recent years (e.g. Bradley, 2020 ; Nicholson, 2014 ; Nicholson & Dupré, 2018 ; Noble, 2020 ; Walsh, 2015 ). She argues agentic plasticity ‘leads’ evolutionary change, with genes acting as ‘followers’ which subsequently stabilise adaptive phenotypic changes (West-Eberhard, 2003 , pp. 157–158). Her analysis makes natural selection an effect of other causes.

These new approaches expose a rift between two competing views of evolution by natural selection: the eighty-year-old gene-stressing MS and its derivatives (e.g. Dennett, 1995 ; Huxley, 1942 ), versus those contemporary views which stress the plasticity of organismic agency, and of phenotypic development, as what guides adaptation. Yet both these rivals claim direct descent from Origin . So we find Dawkins ( 2006 , p. xv, my italics) maintaining that his MS-based selfish-gene view of evolution ‘ is Darwin's theory , expressed in a way that Darwin did not choose but whose aptness, I should like to think, he would instantly have recognized and delighted in.’ Meanwhile, the new ‘developmental’ paradigm of evolutionary biology, writes Walsh ( 2010 , p. 336), ‘preserves more of the core of the Origin of Species than Modern Synthesis Replicator theory does’ (see too West-Eberhard, 2003 , pp. 186–193; 2008 ). In particular, Walsh ( 2012 , p. 192, my italics; drawing on West-Eberhard, 2003 ) argues that a crucial difference between these two Darwinisms is that, while the MS holds natural selection to be a causal force in its own right, developmental or active Darwinism cleaves closer to the Origin in making natural selection— not a cause of evolution, as per the MS view—but ‘a higher-order effect ’ of a number of other causal processes, most notably, of the struggle for existence and of individual development.

Which poses a question: which of today’s two Darwinisms better captures what Origin argues?

Origin ’s framing of natural selection and Darwin’s responses to its critics

The explanatory status of natural selection in Origin does not just concern today’s historians. It worried Darwin himself, particularly in the few months following his book’s launch. Several reviewers—including Darwin’s allies Charles Lyell ( 1859 ), Thomas Huxley ( 1860a , 1860b ) and Asa Gray ( 1860 )—had quickly queried the scientific orthodoxy of the book’s method of argument, and the comprehensiveness of its evidence for its conclusions. Darwin took pains to address these worries, not just in private letters, but in amendments to later editions of Origin , and published defences of its arguments.

In the first edition of Origin , Darwin ( 1859a , pp. 84, 146) habitually wrote as if natural selection were an intelligent agent, ‘intently watching each slight alteration’ in an organism’s structure and habits, so that it could ‘pick out with unerring skill each improvement’:

It may be said that natural selection is daily and hourly scrutinising, throughout the world, every variation, even the slightest; rejecting that which is bad, preserving and adding up all that is good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life.

Writing in this vein, Darwin ( 1859a , pp. 85, 156) cast natural selection as a ‘power,’ which ‘acts by life and death,’ and so ‘causes’ extinction, for example. Not only antagonists (like Adam Sedgwick, 1859), but even allies like Charles Lyell (1860a) and Joseph Hooker ( 1860 ) complained Darwin had cast natural selection as a power akin to a deity, a ‘deus ex machina’ as Hooker ( 1862 ) later put it. Darwin denied the claim. (And later editions of Origin qualified his use of anthropomorphic language.) 1 Yet both the rhetorical organisation of his argument, and the fact that his book used an ordinary language immanently ‘imbued with intentionality,’ weakened these denials (Beer, 2000 , p. 81).

Darwin had launched Origin ’s argument with an account of ‘variation under domestication’ which celebrated the considerable changes in the forms of domesticated plants and animals (especially pigeons) effected by breeders’ powers of ‘artificial selection.’ He then extended this analogy to provide the framework for his exposition of ‘natural selection.’ In so doing, he rhetorically projected an image of ‘nature’s power of selection’ in the form of a human skill, though one of ‘far higher workmanship’ and producing modifications ‘infinitely better adapted to the most complex conditions of life’ than the ‘feeble’ ‘artificial’ efforts of stud-farmers and horticulturalists (Darwin, 1859a , pp. 84, 109). At the same time, when pushed, he strongly resisted the idea that ‘natural selection’ was an anthropomorphic causal agency (Young, 1971 ).

This contradiction arose because, as Beer ( 2000 , pp. xviii, 3, 48) put it, Origin ’s central argument ran directly ‘against the grain of the language available’ to Darwin as a Victorian man of science, a language which spot-lit ‘design and creation.’ Darwin’s struggle was to portray natural law and the uniformity of nature as things opposed to design and divine creation. Thus, viewed in the round—and despite the vagaries of the metaphorical way he had expressed his thesis—his book aimed to convince readers that natural selection was ‘ one general law , leading to the advancement of all organic beings, namely, multiply, vary, let the strongest live and the weakest die’ (Darwin, 1859a , p. 244, my italics; cf. Darwin, 1874 , pp. 48, 613). In 1861, he hastened to underline this aim by adding a caveat to the third edition of Origin ( 1861a , p. 85, my italics):

Several writers have misapprehended or objected to the term Natural Selection. Some have even imagined that natural selection induces variability, whereas it implies only the preservation of such variations as occur and are beneficial to the being under its conditions of life … It has been said that I speak of natural selection as an active power or Deity; but who objects to an author speaking of the attraction of gravity as ruling the movements of the planets? Every one knows what is meant and is implied by such metaphorical expressions; and they are almost necessary for brevity. So again it is difficult to avoid personifying the word Nature; but I mean by Nature, only the aggregate action and product of many natural laws, and by laws the sequence of events as ascertained by us . With a little familiarity such superficial objections will be forgotten.

Natural selection, Darwin here re-asserts, describes a ‘sequence of events as ascertained by us.’ It does not actively produce variations: it results from (the preservation of) variations—such preservation being something which itself ‘ results from the struggle for existence’ (Darwin, 1859a , pp. 5, 433, my italics).

This reading of Origin is reinforced by Darwin’s response to a fierce debate over the explanatory status of ‘natural selection’ in the early months of his book’s life. Origin itself labels natural selection in several ways, most commonly as a principle, a law, or a theory. Within weeks of its appearance, however, both private correspondents and public reviews opened a debate about the causal efficacy of natural selection. Had Darwin’s book proved natural selection to be a true cause (or ‘ vera causa ’) of the origination of species? His friends Huxley ( 1860a , 1860b ) and Gray ( 1860 ), while both hugely appreciative of Origin , concluded that Darwin had failed to prove natural selection was the effective cause of evolution. Others were more contemptuous. Palaeontologist Richard Owen ( 1860 ) pronounced natural selection a hypothesis resting on ‘a purely conjectural basis.’ Philosopher of science John Herschel dismissed Origin as ‘the law of higgledy-piggledy’ (Darwin, 1859b ; Hull, 2003 , pp. 181–182). And Darwin’s old geological mentor Adam Sedgwick ( 1860 , p. 335) found in Origin a ‘baseless theory.’

Darwin ( 1863a ) reacted to these criticisms by pointing out in a letter to the Athenaeum (provoked by Owen, 1863 ) that, though he continued to believe that ‘the theory, or hypothesis, or guess, if the reviewer likes so to call it, of natural selection’ provided the best explanation for the origin of species, such explanation ‘signifies extremely little in comparison with the admission that species have descended from other species and have not been created immutable.’ In short, the chief aim of his book was to win scientific acceptance of the fact that all species of creature were bound together by a web of affinities that comprised a ‘community of descent.’ His exposition of natural selection was first and foremost, aimed to gain assent for the fact of evolution. Its exact explanatory status was of secondary importance.

Meanwhile, behind the scenes, Darwin worked hard to garner evidence which would satisfy Huxley’s doubts about the explanatory status of natural selection. Huxley ( 1860b , pp. 74–75) did not himself use the term ‘ vera causa ’ in his review of Origin . His argument was that Darwin’s thesis on natural selection would remain ‘a hypothesis,’ and not yet a ‘theory of species,’ until ‘positive evidence’ could be produced that a group of animals (or plants) had, ‘by variation and selective breeding, given rise to another group which was, even in the least degree, infertile with the first.’ Besides conducting many (unsuccessful) experiments of his own to prove the sterility of inter-breed hybrids in flowers, Darwin recruited a host of zoologists, botanists and horticulturalists to find evidence to fill the gap that Huxley had identified, including Hooker, Muller, Tegetmeier, Gray and many others—even sending an open letter to the readers of the Journal of Horticulture to beg for relevant facts (Darwin, 1862 ). The chapter on hybridism in the fourth edition of Origin (Darwin, 1866 ) was expanded to discuss the most promising new findings, with the hope of satisfying Huxley. The chapter on hybridism in The Variation of Animals and Plants under Domestication (Darwin, 1868 ) also aimed to answer Huxley’s criticism. And later, the opening paragraphs of the last chapter in the final edition of Origin (Darwin, 1876 ) were enlarged to address the sterility of hybrids. Huxley remained unconvinced.

But Darwin’s strongest and most immediate response to critics of the scientific status of Origin ’s claims was directly to contest the need to prove natural selection a vera causa . Within three months of the book’s publication, he told his closest friend Hooker (Darwin, 1860a ) that Huxley ‘rates higher than I do the necessity of Natural Selection being shown to be a vera causa always in action.’

Darwin contests the need to prove natural selection a vera causa

Three kinds of consideration underlined the subordinate importance of the vera causa criterion for Darwin. Firstly, the exact nature of the standard of proof for a vera causa had been disputed so much over previous decades that, by 1859, its meaning was extremely loose (Ruse, 1975 ). Origin (Darwin, 1859a , p. 423) lampoons the resultant imprecision in scientific identifications of natural phenomena as verae causae : while ‘several eminent naturalists … admit variation as a  vera causa  in one case, they arbitrarily reject it in another, without assigning any distinction in the two cases’—such arbitrary identifications revealing only the power of ‘the blindness of preconceived opinion.’

The inconsistency of scientific judgements about verae causae that Darwin disparaged is confirmed by three trail-blazing historiographical essays (published in the 1970s) which concluded that Origin aimed to prove natural selection a vera causa , in that all three disagree about what Darwin would need to have done to achieve this aim (Hodge, 1977 , 1989 ; Hull, 1973 , 2003 ; Ruse, 1975 , 1999 , p. 57). This disagreement continues today, as Sect.  4 of this paper documents. One historian, Greg Radick ( 2002 , p. 13, my italics), has even glossed Darwin’s adherence to the vera causa ideal as meaning that Origin sought to show that ‘ the causes that together produced natural selection —variation, inheritance and the struggle for existence—were all “true causes,” that is, causes evidenced independently of the facts they were held to explain.’ Radick’s reading—that Origin frames natural selection as the consequence of several other, directly-observable (and hence ‘true’) causal processes—points directly to the argument I advance here. But it stands in stark conflict with the views of the Origin ’s strategy elaborated by Hodge and Ruse in the 1970s, as well as many more recent historiographic claims.

Secondly, Darwin’s own most-repeated criterion for the scientific reality of natural selection was that it could explain the several distinct ‘large classes of facts’ that Origin ( 1876 , p. 568) argued natural selection did explain. This standard of proof was akin to what William Whewell ( 1840 ) called a ‘consilience of inductions’: ‘the best kind of science … comes when different areas of science are brought together and shown to spring from the same principles’ (Ruse, 1975 , p. 163). Yet the status of such consilience vis-à-vis verae causae remains uncertain. According to some historians, such ‘consilience’ was a hallmark of verae causae (Ruse, 1975 , 1999 , p. 58; Waters, 2003 ). Others, like Hodge ( 1989 , pp. 171–173, my italics) argue that Whewell ‘offered his consilience ideal as an alternative ’ to the vera causa ideal.

The ‘large classes of fact’ or ‘different areas of science’ which Origin ( 1859a , pp. 415, 420; 1876 , pp. 137, 424) treats as explained by ‘the same principle’ of natural selection include: the homologous forms of rudimentary, embryological, and anatomical structures in taxonomically related species (e.g. wing of the bat, fin of the porpoise, leg of the horse, human hand); the fact that pre-evolutionary taxonomic classification could be arranged within ‘a few great classes, in groups subordinate to groups, and with the extinct groups often falling in between the recent groups’; endemic species on oceanic islands being related to the nearest source of immigrant species (as in the Galapagos archipelago); the gradual diffusion of dominant forms in the geological record; the co-adaptations of different species to each other within the same habitat; and the lack of perfection of some adaptations—‘the sting of the bee, when used against an enemy, causing the bee’s own death,’ ‘drones being produced in such great numbers for one single act, and being then slaughtered by their sterile sisters,’ ‘the astonishing waste of pollen by our fir-trees’ (Darwin, 1876 , pp. 415, 419).

Darwin reverted to his consilient criterion of proof time and again, not just in Origin , but in his other books (e.g. Darwin, 1874 , p. 24; 1890 , p. 113), and in his letters. For example: ‘It seems to me that an hypothesis is developed into a theory solely by explaining an ample lot of facts’ (Darwin, 1860b ). In contrast, Darwin’s publications never refer to natural selection as a vera causa (nor do they ever refer to it as a mechanism; Ruse, 2005 ). In fact Origin was the only one of his books to reference verae causae at all. It uses the phrase thrice: once to refer to ‘community of descent’; once to suggest that, when a single species occurred at ‘several distant and isolated points,’ the ‘the vera causa of ordinary generation with subsequent migration’ was a better explanation for it doing so than the ‘miracle’ of several separate divine creations; and once, as we just saw, to ridicule the arbitrariness of the assignment to ‘variation’ of the status of a vera causa in the creationist arguments of ‘several eminent naturalists’ (Darwin, 1859a , pp. 159, 352, 482). These three usages all occur in polemics directed at creationists—the last stating directly that naturalists’ identification of verae causae owed more to prejudice than to science. Which might suggest the phrase functioned at best rhetorically in Origin , which variously enlisted, and questioned, its gravitas as a shibboleth of scientific proof.

Thirdly, three months after Origin came out, Darwin discovered a powerful parallel between natural selection and Newton’s law of gravity. In February 1860, Darwin was reading David Brewster’s ( 1855 ) Memoirs of Sir Isaac Newton . This was the month he was most acutely focused on arguments, like Huxley’s ( 1860a ), that Origin had failed to prove natural selection causally efficacious. Brewster ( 1855 , pp. 282ff) recounted how, in 1710, Leibnitz had attacked Newton’s theory of gravity as ‘introducing occult qualities and miracles into philosophy.’ Newton retorted that the theory of gravity was:

proved by mathematical demonstration, grounded upon experiments and the phenomena of nature; and that to understand the motions of the planets under the influence of gravity, without knowing the cause of gravity , is as good a progress in philosophy as to understand the [movements of the clockwork of a clock, as a clockmaker does] without knowing the cause of the gravity of the weight which moves the machine … (Newton, 1711, quoted in Brewster, 1855 , p. 283, my italics)

Darwin pounced on this passage because it underlined a distinction between law and cause, as Darwin swiftly pointed out to Lyell and Gray. Darwin’s ( 1860c ) comment to Lyell was that, though Leibnitz held the law of gravity to be unscientific, mysterious or ‘occult’ (because gravity had not been directly observed), Newton’s law nonetheless added to our knowledge because it explained ‘the movement of wheels of clock, though the cause of descent of the weight could not be explained ,’ adding to Gray the next day (Darwin, 1860d ): ‘This seems to me rather to bear on what you say of Nat. selection not being proved as a vera causa.’

What interested Darwin about Newton’s reply to Leibnitz was that the law of gravity brings under one descriptive formula various ‘sequences of event as ascertained by us’—tidal flows, falling apples, clockwork, and planetary orbits—even though Newton could not say what caused those events. 2 Likewise, the origin of new species by natural selection was too slow to be observed. Yet, like Newton’s law, Darwin’s argument gave coherence to various ‘sequences of event’—palaeontological succession of types, geographical distribution, taxonomic nesting, homologies of anatomical structures in related taxonomic classes, in rudimentary organs and in embryos etc.—however much what caused those events remained open to question.

In the same month that he was reading Brewster, Darwin ( 1860e ) developed a second parallel with physics, this time between his ‘hypothesis’ of natural selection and the wave or ‘undulatory’ theory of light, which, by the 1850s, was becoming increasingly favoured over Newton’s ( 1704 ) corpuscular theory. Of course, no one had ever observed the undulations in the so-called ‘luminiferous ether’ which constituted light, according to Robert Hooke ( 1664 ) and Christiaan Huygens (1690). Yet, said Darwin, the wave theory ‘groups together & explains a multitude of phenomena,’ such as the interference patterns seen in Thomas Young’s ( 1804 ) diffraction experiment, and so was ‘universally now admitted as the true theory.’ ‘The undulatory theory of Light is very far from a vera causa ,’ noted Darwin ( 1860f , my italics), yet it was scientifically ‘allowable (& a great step) to invent the undulatory theory of Light.’ So why should not scientific procedure allow Darwin ( 1860g ) also to ‘invent [the] hypothesis of natural selection … & try whether this hypothesis … does not explain (as I think it does) a large number of facts in geographical distribution—geological succession—classification—morphology, embryology &c. &c.’? 3 By implication, Darwin is here acknowledging that natural selection, while having scientific value, is also ‘very far from a vera causa.’

Darwin’s parallel between the law of gravity and natural selection was swiftly spliced into the last chapter of the third edition of Origin ( 1861a , pp. 514–515), which thenceforth noted that, though ‘the law of the attraction of gravity’ had been attacked by Leibnitz because no one knew ‘what is the essence of the attraction of gravity,’ yet ‘no one now objects to following out the results consequent on this unknown element of attraction.’ Origin ’s final edition saw a further inclusion—Darwin’s ( 1876 , p. 421) parallel between natural selection and the wave theory of light—a parallel which had already been developed at greater length in the exposition of natural selection opening Variation (Darwin, 1868 , vol.1, pp. 8–9). 4

Modern vera causa readings of Origin

I now consider how my reading of Origin bears on evidence for contemporary historians’ conclusion that the main aim of Origin is to prove natural selection has been the ‘true cause’ ( vera causa ), ‘mechanism’ or ‘causal force’ effecting the origin of species (e.g. Gildenhuys, 2004 ; Hodge, 2013 ; Pence, 2018 ; Ruse, 2005 ). It should be remembered that, whilst vera causa interpretations of Origin are widely assumed by today’s Darwin scholars, they disagree amongst themselves as to what vera causa might have meant to Darwin in 1859. Pence ( 2018 ) finds seven current historiographic interpretations of the philosophy of science underpinning Origin —and his list is not exhaustive.

Neither Darwin nor Origin ever claim that natural selection is a vera causa —though, as we saw above, Origin does use this phrase in connection with three other facets of Darwin’s argument. Nor does Darwin anywhere, in his publications, notebooks or private correspondence, say that the book was designed to prove natural selection is a vera causa . On the contrary, he said the book was designed to prove that all species share in a community of descent (besides which, he added, the validity of any claims he had made about natural selection signified ‘extremely little’; Darwin, 1863a , see Sect.  3 ).

So: what evidence do today’s historians advance to back their contention that Darwin wrote Origin to prove natural selection a vera causa ? They largely ignore the evidence I reviewed in Sect.  3.1 , quoting instead the first third of the postscript to a letter Darwin wrote to botanist George Bentham, in May 1863. This letter concerned an address, intended to support Origin , which Bentham was preparing to give to the Linnaean Society (of which he was president) in two days’ time. Bentham (1863, my italics) was worried that Darwin’s theory could not explain why some species of ‘northern hemisphere’ plants were found in Tasmania and Australia’s Victorian Alps to ‘have gone through so many thousand generations in both hemispheres unaltered ,’ whilst other species of such plants had changed so much as to become almost unrecognisable. The postscript to Darwin’s ( 1863b ) reply reads as a kind of executive summary to help the doubting Bentham prepare his imminent address by clarifying three alternative kinds of grounds upon which a belief in natural selection could be based:

In fact the belief in natural selection must at present be grounded entirely on general considerations. (1) on its being a vera causa, from the struggle for existence; & the certain geological fact that species do somehow change (2) from the analogy of change under domestication by man’s selection. (3) & chiefly from this view connecting under an intelligible point of view a host of facts.— When we descend to details, we can prove that no one species has changed: nor can we prove that the supposed changes are beneficial which is the groundwork of the theory. Nor can we explain why some species have changed & others have not … 5

A century later, in 1975, Ruse concluded that this postscript shows that, useful though Darwin believed the analogy between artificial and natural selection might be (Darwin’s 2nd point), ‘the chief proof for Darwin of the truth of his theory was that it had explanatory power in all of these many diverse areas’ (Darwin’s 3rd point). In a footnote to the same article, Ruse ( 1975 , p. 177) challenged the import of the postscript’s first point, saying that, although Darwin here ‘wrote of natural selection as a vera causa ,’ by 1859 this term ‘was used almost as loosely as “deduction”.’ Elsewhere, however, both in his 1975 article and in later works, Ruse ( 1975 , p. 175; 1999 ; 2005) agrees with Hodge ( 1977 , p. 238) that in Origin , Darwin was ‘committed’ or ‘desperately keen’ to show that ‘his evolutionary reasonings were based on a vera causa , natural selection.’ Yet these two historians disagree as to whether Darwin’s ‘commitment’ was informed by John Herschel’s interpretation of Thomas Reid’s understanding of vera causa (Hodge, 1977 , 1989 ), or by the incompatible views (according to Hodge, 1989 , p. 172) of William Whewell (Ruse, 1975 , 1999 ).

Hodge ( 1977 , pp. 240–241; Hodge, 1989 , p. 190; 2013, p. 2273) also disagrees with Ruse about Darwin’s postscript to Bentham. He reads its three points as a rationale for decoding Origin ’s entire structure as something rooted in a three-step strategy to prove natural selection is a vera causa (a strategy which I will describe shortly). Gildenhuys ( 2004 , pp. 594, 605) and Pence ( 2018 ) also ground their arguments on the postscript (though both disagree with Hodge’s reading). None of these articles by Ruse, Hodge, Gildenhuys, or Pence, which cite the postscript to Bentham, discusses the far more substantial correspondence Darwin had had in the opening months of 1860, regarding the causal status of natural selection (discussed in Sect.  3.1 ). Nor do they reference the changes Darwin made to the third and later editions of Origin , reflecting the lasting importance of the points made in that correspondence.

Whether in his publications, his notes or his correspondence, Darwin rarely mentioned verae causae. His only published mention of a vera causa prior to its appearance in Origin was twenty years earlier, in his geological ‘Observations on the Parallel Roads of Glen Roy’ (Darwin, 1839 ; see Sect.  5.1 below). This paper had over-confidently (and falsely) identified the action of river deltas flowing into the sea as a vera causa for the formation of the ‘buttresses’ found below Glen Roy’s ‘parallel roads,’ a deduction Darwin later accounted ‘a great failure, and I am ashamed of it’ (Darwin, 1958 , p. 84). Bar Origin , none of his other books or papers mention verae causae. The sixty plus years of his vast correspondence contain just nine mentions of verae causae. Seven of these occur in the vera causa debate about natural selection during the five months after the book came out—all of which dispute ‘the necessity of Natural Selection being shown to be a vera causa always in action’ (Darwin, 1860a ; see Sect.  3.1 ).

Darwin’s last ever use of the term vera causa is in the oft-cited postscript to Bentham. This comes more than three years after his earlier flurry of correspondence about the causal status of natural selection. By May 1863, Darwin ( 1861a , 1861b ) had re-edited the text of Origin to underline his distinction between cause and law, and now believed that, among his scientific allies, there were many who had accepted natural selection was a vera causa (whatever that meant), including John Stuart Mill. 6 He also knew that many other eminent men of science (including Huxley, Sedgwick, Owen, and Whewell) continued to deny it this status. So, when he noted to Bentham (a worried ally) that the belief in natural selection ‘must at present be grounded entirely on general considerations,’ he did not , in so many words, claim that natural selection was a vera causa . Because, as his whole letter underlined—and the much-quoted postscript reiterates 7 —he knew that there could be no direct observational evidence (‘details’) that even ‘one species has changed.’ Even for those who believed natural selection to be a vera causa , its status as such could only be deduced from things that could be observed (which, according to some interpretations of the concept, disqualified it as a vera causa , because, in the words of one critic, his theory was ‘not inductive —not based on a series of acknowledged facts’; Sedgwick, 1860 , p. 334).

The postscript’s first point therefore acknowledges that, at best, natural selection’s status as a vera causa could only be derived indirectly from observational evidence for ‘the struggle for existence; & the certain geological fact that species do somehow change.’ It was for this reason that—though the analogy between artificial and natural selection provided another possible rationale—the postscript went on to stress that, for Darwin , the chief basis for a belief in natural selection was not that it was a vera causa , but consilience : its ‘connecting under an intelligible point of view a host of facts’ (see Sect.  3.1 ).

Claims that Origin is structured to prove natural selection a vera causa are further weakened by Hodge’s (e.g. 1977 , p. 239; 1992 ; 2013 ) own efforts to force the book into the three-step framework he deems such a proof should take: ‘in explaining any phenomenon, one should invoke only causes whose existence and competence to produce such an effect can be known independently of their putative responsibility for that phenomenon.’ This implies, says Hodge, that Origin should comprise three sections, each section containing a group of chapters evidencing in turn: the existence of natural selection; the competence of natural selection to produce species-change; and, finally, evidence that natural selection really had been responsible for species-change. ‘Unfortunately,’ says Hodge ( 1977 , pp. 238, 242), Origin ‘violates’ this structure, ‘misleadingly’ making ‘successive departures’ from it—departures which ‘were eventually enough to render the strategy and organization of his most famous book unhelpfully and quite unnecessarily obscure.’Which means the three ‘general evidential considerations’ upon which Darwin should have focused, ‘ do not map onto the Origin ’s three clusters of chapters’ (Hodge, 1977 , p. 244; 2013 , p. 2274, my italics).

Origin on what effects natural selection

Modern debates about Darwin’s putative ‘commitment’ to the vera causa principle and his associated ‘epistemological self-consciousness’ (e.g. Hodge, 1977 , p. 238; 2000, p. 29) attain a high degree of philosophical sophistication—far higher than any discussion to be found in Darwin’s own writings. Historiographers and philosophers of science make superfine distinctions between the epistemologies that are deduced to have influenced, or not to have influenced, Darwin’s authorial consciousness. Against this, Hull’s ( 1973 , 2003 ) essays repeatedly demonstrate how shallow an understanding of epistemological issues—and the arguments of contemporary philosophers of science like Mill—Darwin (and Huxley) actually possessed.

As Darwin’s autobiography (1958, p. 140) candidly admitted, ‘my power to follow a long and purely abstract train of thought is very limited.’ And while he did pay some attention to metaphysical subjects in his twenties, his attitude to the topic had become increasingly jaundiced as his reading progressed. During 1838, he spent several months absorbing the opinions of Hume, Mackintosh, Abercrombie, Comte and Ferrier, all of whom belittled metaphysics as, for example, ‘a name of reproach and derision’ (Mackintosh, 1830 , p. 4). By October of that year, he had concluded that: ‘To study Metaphysics, as they have always been studied appears to me to be like puzzling at astronomy without mechanics … we must bring some stable foundation to argue from’ (Darwin, 1838 , p. 5). In later years his use of the term ‘metaphysical’ became derogatory. 8 Books or articles that his letters dubbed ‘metaphysical,’ were condemned as ‘mere verbiage,’ being ‘barely intelligible,’ dealing in ‘far-fetched analogies,’ and constituting ‘rubbish’ produced by a ‘wind-bag’ with ‘muddled... brains’ and ‘an entire want of common sense’ (Darwin, 1845 , 1857 , 1860h , 1861b , 1864 , 1871 , 1874 , p. 78).

Given the improbability that Darwin adhered to a refined philosophical understanding of what vera causa meant when he used the term, I now try to decode what it did mean to him. First, by emphasising the most obvious common denominator in the various conflicting philosophical understandings of verae causae current in his day. And second, by examining what Darwin assumed on the few occasions when he himself did mention verae causae .

Despite a slim evidential basis, modern Darwin scholars have imaginatively constructed several contrasting pedigrees for Darwin’s understanding of verae causae —whether via Thomas Reid (Hodge, 1989 , p. 171), William Whewell (Ruse, 1975 ), John Herschel (Gildenhuys, 2004 ; Pence, 2018 ), or Charles Lyell (Rudwick, 2005 ; Sponsel, 2018 ). Whatever the merits of these different genealogies, all four hypothesised sources share one stress: the need for first-hand observational evidence in establishing the existence of a true cause. Reid insisted on ‘direct experiential acquaintance … as the only acceptable form of evidence for the known truth, reality or existence of a cause’ (Hodge, 1989 , p. 169). Whewell (like Sedgwick and Huxley) objected to Origin because no-one could ‘adduce a single example of one species evolving in nature into another. Nor had plant and animal breeders, through all their efforts, succeeded in producing a single new species’ (Hull, 2003 , p. 184). Herschel ( 1830 , #138) held that the best way of establishing a vera causa was from ‘experience [showing] us the manner in which one phenomenon depends on another in a great variety of cases.’ And Lyell’s uniformitarianism leant on the argument that causes which we can directly observe in the present , like the slow action of coastal waves, can be used to reconstruct the vast prehuman past as recorded in rock strata, so long as we assumed that ‘the same causes … had been at work with the same intensities and in the same overall circumstances’ from the time the first rock formed through to the most recent (Hodge, 2000 , pp. 28–29).

Darwin’s own usage of ‘ vera causa ’

Turn to Darwin’s own usage of ‘ vera causa ’ and we also find a stress on direct observation. His ill-fated Glen Roy paper explains the ‘buttresses’—flat-topped accumulations of alluvial gravel and other debris below the lowest of the parallel roads (see Fig.  1 ) —as left-over ‘deltas’ made by rivers or ‘streamlets.’ These streamlets he deemed to have formed the deltas or ‘raised beaches’ of the roads themselves, at the level which the streamlets flowed into the sea before the Glen was tectonically raised above present-day sea-levels by a sequence of crustal uplifts. (Darwin argued that the problematic lower-level buttresses must be remains of alluvial deposits made by the deltas of these same streamlets after further, less dramatic, crustal liftings of the land.) In this way, he exploited the easy-to-observe fact of the alluvial action of river deltas, which was already a central plank of previous geological explanations for the parallel roads (Rudwick, 1974 , pp. 106–107). Darwin’s paper (1839, p. 52) sums up this step in its argument by confidently asserting: ‘no one can doubt [t]hat this intervening cause [delta formation by rivers] has been … a  vera causa .’

Darwin’s ( 1839 ) illustration of the parallel roads of Glen Roy. The ‘buttresses’ are depicted by bent lines which represent bulging piles of rocky debris (e.g. below the lowest of the three roads)

His only other non- Origin -related use of the phrase was in a letter to William Redfield in February 1840. Redfield ( 1839 ) had just published an article relating ‘a few cases in which whirlwinds of great activity and violence appeared to have resulted from the action of fires.’ Darwin, who had long puzzled over the origin of waterspouts seen on his Beagle voyage, added an observation to Redfield’s list. This regarded a whirlwind and waterspouts resulting from an island-forming, submarine, volcanic eruption, observed by a Captain Tilliard off the Azores in June 1811. 9 Darwin ( 1840 ) wrote: ‘Taking your account of the whirlwinds produced by artificial fires, we here see the vera causa of one set of waterspouts.’

In Darwin’s response to Huxley’s critique of Origin , he also construes what he summarised as Huxley’s demand to prove natural selection a vera causa as a demand to produce what Huxley would recognise as ‘positive’ observational evidence (Sect.  3 ). Witness Darwin’s persistent efforts to produce such evidence from plant-experiments in his own garden, as well as from other horticulturalists and animal-breeders, to prove that domestic breeds had separated so far as to be ‘sometimes sterile with other breeds’ (e.g. Darwin, 1863b ; see Sect.  3 ).

It is this observation-based sense of evidence which informs the chapter-plan of Origin . Because, of course, as the latter two-thirds of the postscript to Bentham confirm, Origin ’s proposed ‘principle,’ ‘hypothesis,’ ‘theory’ or ‘general law’ of natural selection could never be observed to produce the detailed results Darwin’s book claimed that it had produced. The origination of new adaptations and new species was a process which the book held to take anything from ‘many thousands’ to ‘an almost infinite number’ of successive generations (Darwin, 1859a , pp. 114, 481). 10 Hence, as when Lyell’s Principles set out the geological processes observable in the here and now by which he would explain the formation of geological features dating from the earth’s remotest past (Rudwick, 1970 ), Origin sets out from what could be empirically witnessed in order to deduce what could not be witnessed.

Origin ’s presentation of natural selection

Origin ’s first three chapters elaborate several sets of empirical ‘laws,’ that is, statements based on repeated observations that describe (and thus predict) a ‘sequence’ of natural events: ‘laws of inheritance’ (Ch.1); laws of ‘variability’ and ‘correlated growth’ (Ch.2); and the law or ‘doctrine’ of Malthus, that populations of plants and animals have the reproductive capacity to increase at a ‘geometrical ratio,’ whilst food supplies, at best, increase at an arithmetical rate, resulting in a ‘struggle for existence’ (Ch.3). Each of these chapters details the many kinds of observable event which the said laws cover, giving copious examples. The laws themselves—whether of inheritance or variation—are, for ‘the most part unknown,’ or, at best, ‘dimly understood,’ Origin says (Darwin, 1876 , pp. 9–10). Yet, the existence of the phenomena these laws are meant to describe is hard to question, given the detailed observations and experiments Origin recounts regarding: the facts of inheritance in domesticated varieties of animal and plant; the multitudinous variability or ‘individual differences,’ whether in wild species, subspecies and varieties or in domestic breeds; and of the various kinds of competition and mutual aid (as in ‘social plants’) entailed in what Darwin underlined was a ‘metaphorical’ struggle between members of the same and different species to survive, thrive, and reproduce (Darwin, 1859a , pp. 62–63, 70–71).

Whilst inheritance and variability were necessary preconditions for natural selection, its principle engine was the struggle for life, which would winnow the more useful variations in a given habitat from the less. This struggle was a theoretical construct in Malthus. The aim of Origin ’s third chapter was to line up ‘better evidence on this subject than mere theoretical calculations, namely … numerous recorded cases,’ showing both species’ explosive potential for fecundity, and the vulnerability of individuals to a variety of environmental and inter-organism challenges (Darwin, 1859a , p. 64). Chapter Three particularly stresses the ‘web of complex relations’ between different creatures’ fates and those of the other organisms in their habitat (Darwin, 1859a , p. 73). Importantly, this metaphorical ‘struggle for life’ did not just betoken competition, but relative reproductive success and, the ‘dependence of one being on another,’ whether from different species (as with the symbiosis between moths and orchids), or from the same species, as with ‘social plants’ and ‘social animals’ who render ‘mutual aid’ to one another (Darwin, 1876 , p. 50; Bradley, 2020 ).

The logical dependence of Origin ’s fourth chapter, ‘Natural Selection’—and the book’s central thesis—on its first three chapters (on inheritance, variation, and the struggle for existence respectively) is reiterated throughout the book, from its first pages 11 :

As many more individuals of each species are born than can possibly survive; and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form (Darwin, 1859a , p. 5, my italics;).

Through exegesis of its central argument:

… it may be asked, how it is that varieties, which I have called incipient species, become ultimately converted into good and distinct species, which in most cases obviously differ from each other far more than do the varieties of the same species? How do those groups of species, which are called distinct genera, and which differ from each other more than do the species of the same genus, arise? All these results … follow inevitably from the struggle for life (Darwin, 1859a , p. 61, my italics)

To its last page:

It is interesting to contemplate a tangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent upon each other in so complex a manner, have all been produced by laws acting around us. These laws, taken in the largest sense, being Growth with reproduction; Inheritance which is almost implied by reproduction; Variability from the indirect and direct action of the conditions of life, and from use and disuse; a Ratio of Increase so high as to lead to a Struggle for Life, and as a consequence to Natural Selection , entailing Divergence of Character and the Extinction of less improved forms (Darwin, 1859a , pp. 489-490, my italics).

Such dependence is unavoidable, given the impossibility of gathering within a single human lifetime any eyewitness evidence for the efficacy of natural selection. This logic impels us to reject any claim that Origin makes ‘successive independent evidential cases … for natural selection existing at present ’ (e.g. Hodge, 2000 , p. 30). Such a statement would only make sense if natural selection were already assumed to be the consequence of the contributory laws copiously evidenced to ‘exist at present’ in the book’s opening three chapters—precisely the assumption writers like Hodge aim to overturn.

To underline this point, witness a crucial contrast between the first three chapters and the fourth. Unlike its predecessors, the supporting materials in Chapter Four ‘Natural Selection’ are not the fruit of first-hand observation, being presented entirely in the form of ‘ imaginary illustrations’ (Darwin, 1859a , p. 90, my italics; Bradley, 2011 ).

It is not until the latter parts of the fourth chapter that Origin starts seriously to discuss the causes for the laws evidenced in the book’s first three chapters— and thus of natural selection. The causal mechanism producing the laws of inheritance (i.e. the transmission of heritable characters) is bypassed. 12 Instead Chapters Four, Five (‘Laws of Variation’) and Six (‘Difficulties of the Theory’) proceed to explicate several causal processes that produce variations . Here, pride of place goes to the role of changed habits in directing selection. This theme stands out in Chapter Four’s illustrations of Darwin’s ‘principle of divergence’ of character (cf. adaptive radiation): Origin asks us to imagine the case of a carnivorous quadruped, ‘of which the number that can be supported in any country has long ago arrived at its full average’:

If its natural power of increase be allowed to act, it can succeed in increasing (the country not undergoing any change in conditions) only by its varying descendants seizing on places at present occupied by other animals: some of them, for instance, being enabled to feed on new kinds of prey, either dead or alive; some inhabiting new stations, climbing trees, frequenting water, and some perhaps becoming less carnivorous.

Darwin ( 1859a , p. 179; 1876 , p. 8) formalized this habit-first causal process for the evolution of transformative adaptations—as when ‘a land carnivorous animal’ had been ‘converted into one with aquatic habits’—in a way that showed how ‘changed habits produce an inherited effect.’ Origin ’s clearest example of this non-Lamarckian process highlighted how ‘transitional habits’ had plausibly resulted in the evolution of flying squirrels 13 :

Origin (Darwin, 1859a , pp. 179–186) asks us to imagine that, a long time ago, some adventurous, flightless squirrel-ancestors had formed a new habit of launching themselves, not just from branch to branch, but from tree-top to tree-top. Tree-surfing would put a new premium on glide-friendly changes to the squirrels’ physique (stronger spring at take-off, better depth vision, lighter body-weight, more aerodynamic tail, broader flanges of skin between front and back legs). Any chance heritable variation that fitted them better to their novel habit would have increased their reproductive success compared to unchanged conspecifics. Hence, ‘it would be easy for natural selection to fit the animal, by some modification of its structure, for its changed habits.’ Thus, while the production of what we now know as genetic variations—which must have stabilized the bodily changes that make tree-surfing easier for squirrels—might be random, the direction of adaptation would be set by the non-random agentic innovations of the ancestral squirrels.

‘Changed habits’ included ‘use and disuse,’ not just in animals but in plants. Of changed habits in plants, Darwin ( 1859a , pp. 139–143) cited the ‘acclimatisation’ of, for example, ‘the pines and rhododendrons, raised from seed collected by Dr. Hooker from trees growing at different heights on the Himalaya, [which] were found in this country to possess different constitutional powers of resisting cold’—seeds taken from higher in the mountains being found habitually more resistant to chilly British weather than their cousins from the mountains’ lower slopes. Darwin (e.g. 1859a , p. 76) typically framed the qualities of an organism in terms of ‘strength, habits, and constitution.’ The fate of variations in anatomy very often depend on an organism’s habits, according to his accounts, as, for example, with: the displays that feature sexual ornaments and the fights, which, he argued, must have led to the sexual selection of tusks and other weapons of sexual rivalry; the eating habits of birds with different shaped bills (e.g. finches in the Galapagos archipelago; Lindholm, 2015 ); insects’ adaptations to feeding from and so pollinating certain species of flower; closely-related animal species avoiding hybridisation by ‘haunting different stations’ of a given habitat; or the growth of hardness in pigeon chicks’ beaks (used for cracking their way out of their egg) (Darwin, 1859a , pp. 87, 103; 1882 ).

Other causes of variability proposed by Origin included ‘direct action of the environment’—on the ‘plastic’ (Darwin’s word: 1876 , pp. 62, 106, 438) quality of the reproductive system, and the creature’s ‘whole organisation.’ Such action depended both on the nature of the organism and the nature of the conditions (e.g. climate, altitude), the nature of the organism being ‘much the more important,’ according to Darwin ( 1876 , p. 6)—an emphasis now re-echoing through today’s post-MS biology with its so-called ‘return to the organism’ (e.g. Lewontin, 1983 ; Nicholson, 2014 ; Walsh, 2015 ).

Finally, the domain of phenotypic variability is not coextensive or neatly aligned with those ‘variations’ of relevance to a theory of natural selection. Not only may some of the ordinary doings of organisms fail to impinge on the struggle for existence—‘the war of nature is not incessant’ (Darwin, 1859a , p. 79). Even those that do so impinge may not result solely in ‘advantages,’ but also—as Chauncey Wright ( 1870 , p. 293) argued—‘limiting disadvantages,’ likely to undermine fitness. The Descent of Man (Darwin, 1874 , p. 571) proposed that Wright’s argument had ‘an important bearing on the acquisition by man of some of his mental characteristics’—citing in illustration how processes that (adaptively) ensured group cohesion, could simultaneously foster maladaptive customs and superstitions in some peoples. Examples included tribes where infanticide and cannibalism were customary, as reported by some ethnographers, plus, in Darwin’s own society, mating choices based on ‘mere wealth or rank’ (Darwin, 1874 , pp. 121–122, 617).

Given Darwin’s identification of verae causae with processes that can be directly observed, it makes sense that he should have structured Origin to prove the existence of natural selection—something unobservable —as being a higher-order consequence of other observable (causal) processes. To recognise Origin presents natural selection as an effect of other causes, not a cause in its own right, is not merely a matter of textual exegesis, however. Such recognition has dramatic repercussions for the contemporary interpretation of evolutionary theory: because it fells the central pillar of gene-based MS constructions of the natural world—the belief that evolution is caused by natural selection. This forces on evolutionary scientists the need to seek a brand new conceptualisation of the relationship between evolution and what Walsh ( 2015 , Ch.2.1) calls ‘the normal activities of organisms,’ including ourselves.

Here, the uptake of evolutionary theory by psychologists furnishes an apt illustration. Psychology is the central scientific site for examining the normal activities of organisms, particularly of human beings. So, how would adoption of the view that natural selection is ‘an analytic consequence’ (Walsh, 2015 , Ch.2.1) of the normal lives of organisms alter contemporary evolutionary psychologies? Most significantly, it would disconnect how evolutionary science approaches the study of behaviour from any constraint by ideas about how natural selection operates (e.g. the need to calculate ‘inclusive fitness’; or to speculate about a prehistoric ‘environment of evolutionary adaptedness’; Buss, 2009 ; Tooby & Cosmides, 2016 ). Because, as Walsh ( 2015 , Ch.2.1) says, ‘given the normal activities of organisms, nothing needs to be added [to our theoretical framework] to get populations to change in the ways that Darwin describes as natural selection.’ Which represents a complete reversal of those tenets of evolutionary psychology that produce statements like these (italics mine):

Like vision and language, our emotions and cognitive faculties are complex, useful, and non-randomly organized, which means that they must be a product of the only physical process capable of generating complex, useful, non-random organization, namely, natural selection (Pinker, 2005 , p. xiv).

Because mental phenomena are the expression of complex functional organization in biological systems, and complex organic functionality is the downstream consequence of natural selection , then it must be the case that the sciences of the mind and brain are adaptationist sciences, and psychological mechanisms are computational adaptations (Tooby & Cosmides, 2016 , p. 11).

[The brain’s] programs were designed not by an engineer, but by natural selection, a causal process that retains and discards design features based on how well they solved adaptive problems in past environments (Tooby & Cosmides, 2016 , p. 19).

If natural selection is not an ‘upstream’ causal process which produces psychological phenomena, but a ‘downstream consequence’ of the normal activities of organisms—only some of which have adaptive consequences (cf. Chauncey Wright, above)—then our theoretical attention must switch from claims about natural selection, to the need adequately to conceptualise how agency manifests itself in the natural world. Perhaps we should not be surprised, therefore, that when we examine how Darwin himself presented his studies of various creatures’ ‘habits’ or behaviour—human group-processes and facial expressions; sexual displays in animals; worms’ intelligence and the motility of the ova of Flustra ; mutual aid among social animals and the problem-solving movements of plant growth—we find these all reflect a single, coherent vision. According to Darwin (e.g. 1859a, p. 61), any studied habitat is maintained by the ‘infinitely complex’ web of actions and reactions linking the habits of the focal organism ‘to other organic beings and to external nature.’ It is this vision of the interdependencies created and maintained by agency which underpins how Darwin construed what he called ‘the struggle for life,’ and, as a consequence, how he understood natural selection (Bradley, 2020 ).

The idea that natural selection is the causal force or mechanism which produces evolutionary adaptations and originates new species remains for many a scientific truism, thanks to the continuing appeal of ‘genes-eye’ MS accounts of evolution. This essay rejects a corresponding truism in Darwin scholarship, which holds that the main aim of Origin ’s (Darwin, 1859a , p. 459) ‘one long argument’ is to prove natural selection the causal mechanism or vera causa responsible for the evolution of adaptations and new species. 14 Specifically, I show how modern historiographic constructions of Darwin’s supposed authorial ‘intention,’ ‘desperation,’ or ‘commitment’ to prove natural selection a vera causa in Origin are built on an unnecessarily selective sample from what Darwin himself wrote about verae causae , typically highlighting just one remark, comprising the first third of Darwin’s ( 1863b ) brief postscript to a letter to George Bentham.

My starting-point was different. I began by examining the context for all Darwin’s known uses of the term ‘ vera causa .’ From this beginning I have argued that, provided one grounds one’s views of Origin ’s arguments upon: how Darwin himself used the term vera causa (as requiring first-hand observational evidence); how this usage conforms to the commonest meaning of the term among Victorian philosophers of science; how Origin itself sets up, and repeatedly restates, the logical dependence of natural selection on inheritance, variation and the struggle for life; how, responding to criticism early in 1860, Darwin disputed the need to prove natural selection the true cause of adaptive change and evolution; and how that dispute led him to revise later editions of the book—then one must conclude that, according to Darwin, natural selection is an effect of other causes, not a cause in its own right.

One advantage of recognising that Origin does not comprise just one argument—aimed at proving natural selection the true cause of adaptation—is to re-focus historiographic and scientific attention on all the other arguments that the book makes. Several of these arguments have become central to evolutionary science over the last twenty years, though often without any awareness by modern scientists of antecedent arguments in Origin . 15 These include the leading role played by organisms’ agency in the genesis of adaptations (cf. ‘transitional habits’ aka the ‘Baldwin effect,’ ‘genetic accommodation,’ and ‘niche construction’: Darwin, 1876 , pp. 138–143; Gould, 2002 , pp. 125–127; Noble & Noble, 2017 ; Noble, 2021 ; Odling-Smee et al., 2003 ; Walsh, 2015 ); the importance of plasticity of structure in the evolution of new adaptations (Darwin, 1876 , pp. 62, 106, 438; West-Eberhard, 2003 ; 2008 ); the direct effect of external conditions (Darwin, 1876 , p. 67; Gilbert & Epel, 2015 , pp. 435ff); the recognition that ‘inheritance’ includes ‘two distinct processes’—the transmission of heritable characters from parent to offspring and their development (Darwin, 1876 , pp. 114–15, 119–122; 1874 , p. 227; Walsh, 2010 ); and multi-level selection (Darwin, 1876 , pp. 67–68; Wilson & Wilson, 2007 ).

As soon as contemporary scientists accept that, as per Darwin’s argument in Origin , natural selection does not cause, but results from the ordinary activities of organisms, contemporary evolutionary theorists must address a new foundational challenge: the need to construct a viable, evidence-based picture of the natural world as what I have called a ‘theatre of agency’ (Bradley, 2020 ). Only when they have such a picture will scientists be in a position to work up an intelligible account of natural selection. The pioneering instance of such a working-up constitutes a theme central to Darwin’s many publications.

Acknowledgements

With thanks to Michael Ruse for a stimulating email correspondence on this topic, and to Jane Selby for help and discussion throughout.

Open Access funding enabled and organized by CAUL and its Member Institutions.

Declarations

I have no conflicts of interest. Research was self-funded.

1 E.g. the third edition of Origin (Darwin, 1861a , p. 88, my italics) adjusted the above quotation to begin: ‘ It may metaphorically be said that natural selection is daily and hourly scrutinising, throughout the world …’.

2 Physicists still debate what causes the phenomena the law of gravity describes. At least fourteen theories of gravity are currently in play.

3 NB Darwin here denies that the undulatory theory of light identifies a ‘vera causa’ on the grounds that ethereal undulations had never been observed. In this he equates verae causae with demonstration by positive observational evidence (as discussed later in this section). Conversely, Darwin also implies that causal hypotheses (e.g. ‘interference patterns result from the wave-form of light’) do not have to equate to verae causae . Hence the need for my examination of the way the argument in Origin is presented to prove my case that he cast natural selection as a consequence of other causes (see Sect.  5.2 below).

4 Note that controversy over the causal status of natural selection was still live in 1870: ‘Strictly speaking, Natural Selection is not a cause at all, but is the mode of operation of a certain quite limited class of causes’: Chauncey Wright, ‘Review [of Contributions to the Theory of Natural Selection. A Series of Essays by Alfred Russell Wallace],’ North American Review111, (1870), p. 293.

5 It is notable that this postscript is never quoted in full by the authors I have cited. All stop before the words, ‘When we descend to details …’ Even I have not quoted its two final sentences, viz. ‘The latter case seems to me hardly more difficult to understand precisely & in detail than the former case of supposed change. Bronn may ask in vain the old creationist school & the new school why one mouse has longer ears than another mouse—& one plant more pointed leaves than another plant.'

6 Hull ( 1973 , pp. 7–8; 2003 , pp. 185–188) argues that Darwin was mistaken in this belief, at least where Mill was concerned.

7 Albeit in its second paragraph, which historiographers seldom if ever quote or discuss—as noted previously.

8 A contributing factor here may have been Darwin’s growing sense that his Glen Roy ( 1839 ) paper had been a ‘gigantic blunder.’ According to Barrett ( 1973 , p. 24) Darwin came to the conclusion that it was ‘metaphysics’ that ‘had tripped him.’ Hence his determination that this ‘didn’t happen again.’.

9 This eruption gave birth to Sabrina Island.

10 This difficulty was even more acute than with Newton’s law of gravity. Yes, gravity was indeed invisible, and had an unknown causal mechanism. But its putative effects can be observed and measured here and now: pendulums swinging; apples accelerating towards earth; tides rising and falling; planets orbiting. Natural selection could neither be observed in itself. Nor could the immensely slow production of its putative effects be observed in the span of any one human lifetime.

11 Or, indeed, arguably from its title , which equates, ‘the origin of species by means of natural selection,’ with ‘the preservation of favoured races in the struggle for life.’

12 A causal mechanism for inheritance is tentatively presented in the last chapter of Variation under Domestication (Darwin, 1868 ), titled: ‘Provisional hypothesis of pangenesis,’ though this hypothesis was never incorporated or mentioned in later editions of Origin.

13 This process was supposedly only discovered after Darwin’s death, by James Mark Baldwin in 1896 (similar formulations were advanced at about the same time by Conway Lloyd Morgan and others). As a result it is now known as ‘the Baldwin effect’ (after Simpson, 1953 ). However, Baldwin ( 1909 , p. 11) explicitly denied that he had discovered this process, which he called ‘organic selection,’ because, he said, Origin had clearly described it in 1859, under the heading ‘transitional habits.’

14 The very idea that this claim of Darwin’s ( 1859a , p. 459)—that Origin comprised ‘one long argument’—espoused a sober epistemological commitment, arguably misrecognises its rhetorical, not to say wishful, status. In her commentary, Beer’s ( 2000 , pp. 42–43) reminds us how Origin ’s ‘argument’ does not proceed according to an epistemological schema, but rather by laboriously accumulating ‘an unruly superfluity of material’ through ‘a strange intermingling of acquisition, concretion, analogy and prophecy.’ Hence, it is ‘only gradually and retrospectively,’ she says, that ‘the force of the [‘one long’] argument emerge[s] from the profusion of example.’.

15 There are several exceptions to this claim, most notably for me; Mary Jane West-Eberhard ( 2003 , 2008 ).

The origiinal online version of this article was revised: Missing Open Access funding information has been added in the Funding Note.

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

• Arthur W. The emerging conceptual framework of evolutionary developmental biology. Nature. 2002; 415 :757–764. doi: 10.1038/415757a. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Baldwin, J. (1909). Darwin and the humanities . Review Publishing.
• Barrett PH. Darwin's 'gigantic blunder'. Journal of Geological Education. 1973; 21 :19–28. doi: 10.5408/0022-1368-21.1.19. [ CrossRef ] [ Google Scholar ]
• Bateson W. Mendel's principles of heredity. Cambridge University Press; 1909. [ Google Scholar ]
• Beer G. Darwin's plots: Evolutionary narrative in Darwin, George Eliot and nineteenth-century fiction. 2. Cambridge University Press; 2000. [ Google Scholar ]
• Bradley B. Darwin's sublime: The contest between reason and imagination in On the origin of species . Journal of the History of Biology. 2011; 44 :205–232. doi: 10.1007/s10739-009-9210-3. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Bradley B. Darwin's psychology: The theatre of agency. Oxford University Press; 2020. [ Google Scholar ]
• Brewster, D. (1855). Memoirs of the life, writings, and discoveries of Sir Isaac Newton . Constable &Co.
• Buss DM. The great struggles of life: Darwin and the emergence of evolutionary psychology. American Psychologist. 2009; 64 :140–148. doi: 10.1037/a0013207. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Darwin, C. (1838). Notebook N. http://darwin-online.org.uk/content/frameset?itemID=CUL-DAR126.-&viewtype=text&pageseq=1
• Darwin C. Observations on the parallel roads of Glen Roy, and of other parts of Lochaber in Scotland, with an attempt to prove that they are of marine origin. Philosophical Transactions of the Royal Society. 1839; 129 :39–81. doi: 10.1098/rstl.1839.0005. [ CrossRef ] [ Google Scholar ]
• Darwin, C. (1840). Letter to William C. Redfield. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-556.xml;query=redfield;brand=default
• Darwin, C. (1845). Letter to Charles Lyell, 8th October. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-919.xml
• Darwin, C. (1857). Letter to Joseph Hooker, 25th December. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-2194.xml
• Darwin, C. (1859a). On the Origin of Species by means of natural selection, or the preservation of favoured races in the struggle for life . Murray. [ PMC free article ] [ PubMed ]
• Darwin, C. (1859b). Letter to Charles Lyell, 10th December. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-2575.xml;query=higgledy;brand=default
• Darwin, C. (1860a). Letter to Asa Gray, 24th February. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-2713.xml;query=%27vera%20causa%27;brand=default
• Darwin, C. (1860b). Letter to Asa Gray, 18th February https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-2704.xml;query=ample%20lot%20of;brand=default
• Darwin, C. (1860c). Letter to Charles Lyell, 23rd Feb. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-2707.xml
• Darwin, C. (1860d). Letter to Asa Gray, 24th February. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-2707.xml;query=%27vera%20causa%27;brand=default
• Darwin, C. (1860e). Letter to C.J.F. Bunbury, 9th February. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-2690.xml;query=%27vera%20causa%27;brand=default
• Darwin, C. (1860f). Letter to Charles Lyell, 12th February. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-2693.xml;query=%27vera%20causa%27;brand=default
• Darwin, C. (1860g). Letter to J.S. Henslow, 8th May. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-2791.xml;query=embryology;brand=default
• Darwin, C. (1860h). Letter to Asa Gray, 26th November. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-2998.xml
• Darwin, C. (1861a). On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life (3rd edn). Murray [ PMC free article ] [ PubMed ]
• Darwin, C. (1861b). Letter to Asa Gray, 11th April. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-3115.xm
• Darwin, C. (1862). Letter to the Journal of Horticulture , 25th November. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-3826.xml;query=journal%20of%20horticulture;brand=default
• Darwin, C. (1863a). Letter to Athenaeum , 5th May. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-4142.xml;query=athen%C3%A6um;brand=default
• Darwin, C. (1863b). Letter to George Bentham, 22nd May https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-4176.xml
• Darwin, C. (1864). Letter to Asa Gray, 13th September. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-4611.xml
• Darwin, C. (1866). On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life (4th edn). Murray [ PMC free article ] [ PubMed ]
• Darwin, C. (1868). The variation of animals and plants under domestication Vol. 2. Murray [ PMC free article ] [ PubMed ]
• Darwin, C. (1871). Letter to John Murray, 13th April. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-7680.xml
• Darwin, C. (1874). The descent of man, and selection in relation to sex (2nd edn). Murray.
• Darwin, C. (1876). The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life (6th edn). Murray. [ PMC free article ] [ PubMed ]
• Darwin, C. (1882). The various contrivances by which orchids are fertilised by insects. (2nd revised edition). Murray.
• Darwin, C. (1890). The expression of the emotions in man and animals (2nd edn). Murray.
• Darwin, C. (1958). The autobiography of Charles Darwin, 1809–1882: With original omissions restored . Edited by Nora Barlow. Collins.
• Dawkins R. The selfish gene: 30th anniversary. Oxford University Press; 2006. [ Google Scholar ]
• Dennett D. Darwin's dangerous idea: Evolution and the meanings of life. Simon & Schuster; 1995. [ Google Scholar ]
• Depew DJ, Weber BH. Darwinism evolving: Systems dynamics and the genealogy of natural selection. MIT Press; 1994. [ Google Scholar ]
• Fisher RA. Has Mendel's work been rediscovered? Annals of Science. 1936; 1 :115–137. doi: 10.1080/00033793600200111. [ CrossRef ] [ Google Scholar ]
• Gayon, J. (1992). Darwin et l'apres-Darwin: Une histoire de l'hypothese de selection naturelle . Editions KIME
• Gilbert, S., & Epel, D. (2015). Ecological developmental biology: The environmental regulation of development, health, and evolution (2nd edn). Sinauer Ass.
• Gildenhuys P. Darwin, Herschel and the role of analogy in Darwin's Origin . Studies in the History and Philosophy of the Biological and Biomedical Sciences. 2004; 25 :593–611. doi: 10.1016/j.shpsc.2004.09.002. [ CrossRef ] [ Google Scholar ]
• Gould SJ. The structure of evolutionary theory. Harvard University Press; 2002. [ Google Scholar ]
• Gray A. Review of Darwin's theory on the origin of species by means of natural selection. American Journal of Science and Arts. 1860; 29 :153–184. [ Google Scholar ]
• Griffiths PE, Gray RD. Darwinism and developmental systems. In: Oyama S, Griffiths P, Gray R, editors. Cycles of contingency: Developmental systems and evolution. MIT Press; 2001. pp. 195–218. [ Google Scholar ]
• Hall BJ. Evolutionary developmental biology (evo-devo): Past, present, and future. Evolution: Education and Outreach. 2012; 5 :184–193. [ Google Scholar ]
• Herschel J. A preliminary discourse on the study of natural philosophy. Longman & Co; 1830. [ Google Scholar ]
• Hodge J. The structure and strategy of Darwin's 'long argument'. British Journal for the History of Science. 1977; 10 :237–246. doi: 10.1017/S0007087400015685. [ CrossRef ] [ Google Scholar ]
• Hodge J. Darwin's theory and Darwin's argument. In: Ruse M, editor. What the philosophy of biology is. Kluwer; 1989. pp. 163–182. [ Google Scholar ]
• Hodge J. Discussion: Darwin's argument in the Origin . Philosophy of Science. 1992; 59 :461–464. doi: 10.1086/289682. [ CrossRef ] [ Google Scholar ]
• Hodge J. Knowing about evolution: Darwin and his theory of natural selection. In: Creath R, Maienschein J, editors. Biology and Epistemology. Cambridge University Press; 2000. pp. 27–47. [ Google Scholar ]
• Hodge J. Darwin’s book: On the origin of species. Science & Education. 2013; 22 :2267–2294. doi: 10.1007/s11191-012-9544-7. [ CrossRef ] [ Google Scholar ]
• Hooke, R. (1664). Micrographia: Or some physiological descriptions of minute bodies made by magnifying glasses. With observations and inquiries thereupon. Royal Society.
• Hooker, J.D. (1860). Letter to Charles Darwin, 8th June. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-2825A.xml;query=hooker;brand=default
• Hooker, J.D. (1862). Letter to Charles Darwin, 26th November. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-3831.xml;query=deus;brand=default
• Hugyens, C. (1690). Treatise on light . Pieter van der Aa
• Hull D. Darwin and his critics. University of Chicago Press; 1973. [ Google Scholar ]
• Hull D. Darwin's science and Victorian philosophy of science. In: Hodge J, Radick G, editors. The Cambridge Companion to Darwin. Cambridge University Press; 2003. pp. 168–191. [ Google Scholar ]
• Huxley, J. (1942). Evolution: The modern synthesis . George Allen & Unwin.
• Huxley TH. On species, races and their origin. Journal Proceedings of the Royal Institution of Great Britain. 1860; 3 :195–200. [ Google Scholar ]
• Huxley TH. Darwin on the Origin of Species. Westminster Review. 1860; 17 :541–570. [ Google Scholar ]
• Laland K, Odling-Smee J, Hoppitt W, Uller T. More on how and why: Cause and effect in biology revisited. Biology & Philosophy. 2013; 28 :719–745. doi: 10.1007/s10539-012-9335-1. [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Laland K, Uller T, Feldman M, Sterelny K, Muller G, Moczek A, Odling-Smee J. The extended evolutionary synthesis: Its structure, assumptions and predictions. Proceedings of the Royal Society (series b) 2015; 282 :1–14. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Lewontin R. Gene, organism and environment. In: Bendall D, editor. Evolution from molecules to men. Cambridge University Press; 1983. pp. 273–285. [ Google Scholar ]
• Lindholm M. DNA disposes, but subjects decide: Learning and the extended synthesis. Biosemiotics. 2015; 8 :443–461. doi: 10.1007/s12304-015-9242-3. [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Lyell, C. (1859). Letter to Charles Darwin, 4th October. https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-3132.xml;query=%27vera%20causa%27;brand=default
• Mackintosh, J. (1830). Dissertation on the progress of ethical philosophy, Chiefly during the seventeenth and eighteenth Centuries. Adam and Charles Black, 1862.
• Muller G. Evo-devo: Extending the evolutionary synthesis. Nature Reviews: Genetics. 2007; 8 :943–949. doi: 10.1038/nrg2219. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Newton, I. (1704). Opticks . William Innys.
• Nicholson D. The return of the organism as a fundamental explanatory concept in biology. Philosophy Compass. 2014; 9 :347–359. doi: 10.1111/phc3.12128. [ CrossRef ] [ Google Scholar ]
• Nicholson D, Dupré J, editors. Everything flows: Towards a processual philosophy of biology. Oxford University Press; 2018. [ Google Scholar ]
• Noble D. The role of stochasticity in biological communication processes. Progress in Biophysics and Molecular Biology. 2020; 162 :122–128. doi: 10.1016/j.pbiomolbio.2020.09.008. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Noble D. The illusions of the modern synthesis. Biosemiotics. 2021; 14 :5–24. doi: 10.1007/s12304-021-09405-3. [ CrossRef ] [ Google Scholar ]
• Noble R, Noble D. Was the watch-maker blind? Or was she one-eyed? Biology. 2017 doi: 10.3390/biology6040047. [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Odling-Smee J, Laland K, Feldman M. Niche construction: The neglected process in evolution. Princeton University Press; 2003. [ Google Scholar ]
• Oyama S, Griffiths P, Gray R. Cycles of contingency: Developmental systems and evolution. MIT Press; 2001. [ Google Scholar ]
• Owen R. Review of Origin & other works. Edinburgh Review. 1860; 111 :487–532. [ Google Scholar ]
• Owen, R. (1863). [Anonymous] Letter to Athenaeum , 2nd May.
• Pence C. Sir John F. W. Herschel and Charles Darwin: Nineteenth-century science and its methodology. Hopos: the Journal of the International Society for the History of Philosophy of Science. 2018; 8 :1–35. [ Google Scholar ]
• Pigliucci M, Muller G, editors. Evolution: The extended synthesis. MIT Press; 2010. [ Google Scholar ]
• Pinker S. Foreword. In: Buss DM, editor. The handbook of evolutionary psychology. Wiley; 2005. pp. xi–xvi. [ Google Scholar ]
• Provine WB. Progress in evolution and meaning in life. In: Nitecki M, editor. Evolutionary progress. University of Chicago Press; 1988. pp. 49–74. [ Google Scholar ]
• Radick G. Darwin on language and selection. Selection. 2002; 1 :7–16. doi: 10.1556/Select.3.2002.1.2. [ CrossRef ] [ Google Scholar ]
• Radick G. Is the theory of natural selection independent of its history? In: Hodge J, Radick G, editors. The Cambridge companion to Darwin. 2. Cambridge University Press; 2009. pp. 147–172. [ Google Scholar ]
• Redfield WC. Whirlwinds excited by fire. Edinburgh New Philosophy Journal. 1839; 27 :369–379. [ Google Scholar ]
• Rudwick M. The strategy of Lyell’s. Principles of Geology Isis. 1970; 61 :4–33. [ Google Scholar ]
• Rudwick M. Darwin and Glen Roy: A 'great failure' in scientific method? Studies in the History and Philosophy of Science. 1974; 5 :97–185. doi: 10.1016/0039-3681(74)90024-7. [ CrossRef ] [ Google Scholar ]
• Rudwick M. Lyell and Darwin, geologists: Studies in the earth sciences in the age of reform. Taylor & Francis; 2005. [ Google Scholar ]
• Ruse M. Darwin's debt to philosophy: An examination of the influence of the philosophical ideas of John F.W. Herschel and William Whewell on the development of Charles Darwin's theory of evolution. Studies in the History and Philosophy of Science. 1975; 6 :159–181. doi: 10.1016/0039-3681(75)90019-9. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Ruse M. The Darwinian revolution: Science red in tooth and claw. 2. University of Chicago Press; 1999. [ Google Scholar ]
• Ruse M. Darwinism and mechanism: Metaphor in science. Studies in the History and Philosophy of the Biological and Biomedical Sciences. 2005; 36 :285–302. doi: 10.1016/j.shpsc.2005.03.004. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Sapp J. The nine lives of Gregor Mendel. In: Le Grand H, editor. Experimental inquiries: Historical, philosophical, and social studies of experimentation in science. Kluwer; 1990. pp. 137–166. [ Google Scholar ]
• Sedgwick A. Objections to Mr Darwin’s theory of the origin of species. Spectator. 1860; 24 :285–286. [ Google Scholar ]
• Simpson GG. The Baldwin effect. Evolution. 1953; 7 :110–117. doi: 10.1111/j.1558-5646.1953.tb00069.x. [ CrossRef ] [ Google Scholar ]
• Smocovitis B. Unifying biology: The evolutionary synthesis and evolutionary biology. Journal of the History of Biology. 1992; 25 :1–65. doi: 10.1007/BF01947504. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Sponsel A. Darwin’s evolving identity: Adventure, ambition, and the sin of speculation. University of Chicago Press; 2018. [ Google Scholar ]
• Tooby J, Cosmides L. The theoretical foundations of evolutionary psychology. In: Buss DM, editor. The handbook of evolutionary psychology. 2. Wiley; 2016. pp. 3–87. [ Google Scholar ]
• Walsh D. Two neo-darwinisms. History and Philosophy of the Life Sciences. 2010; 32 :317–340. [ PubMed ] [ Google Scholar ]
• Walsh D. The struggle for life and the conditions of existence: Two interpretations of Darwinian evolution. In: Brinkworth M, Weinert F, editors. Evolution 20: Implications of Darwinism in philosophy and the social and natural sciences. Springer; 2012. pp. 191–209. [ Google Scholar ]
• Walsh D. Organisms, agency, and evolution. Cambridge University Press; 2015. [ Google Scholar ]
• Waters CK. The arguments in the Origin of Species. In: Hodge J, Radick G, editors. The Cambridge companion to Darwin. Cambridge University Press; 2003. pp. 116–142. [ Google Scholar ]
• West-Eberhard MJ. Developmental plasticity and evolution. Oxford University Press; 2003. [ Google Scholar ]
• West-Eberhard MJ. Toward a modern revival of Darwin’s theory of evolutionary novelty. Philosophy of Science. 2008; 75 :899–908. doi: 10.1086/594533. [ CrossRef ] [ Google Scholar ]
• Weber BH, Depew DJ. Developmental systems, Darwinian evolution, and the unity of science. In: Oyama S, Griffiths P, Gray R, editors. Cycles of Contingency: Developmental systems and evolution. MIT Press; 2001. pp. 239–254. [ Google Scholar ]
• Whewell W. The philosophy of the inductive sciences. Parker; 1840. [ Google Scholar ]
• Wilson DS, Wilson EO. Rethinking the foundation of sociobiology. Quarterly Review of Biology. 2007; 82 :327–348. doi: 10.1086/522809. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Wright C. Review [of Contributions to the theory of natural selection. A series of essays, by Alfred Russell Wallace] North American Review. 1870; 111 :282–311. [ Google Scholar ]
• Young R. Darwin's metaphor: Does nature select? The Monist. 1971; 55 :442–503. doi: 10.5840/monist197155322. [ CrossRef ] [ Google Scholar ]
• Young T. The Bakerian lecture: Experiments and calculations relative to physical optics. Philosophical Transactions of the Royal Society of London. 1804; 94 :1–16. [ Google Scholar ]

Home — Essay Samples — Science — Biology — Natural Selection

Essays on Natural Selection

Prompt examples for natural selection essays, the theory of natural selection.

Explain Charles Darwin's theory of natural selection and how it serves as a cornerstone of modern evolutionary biology.

Examples of Natural Selection in the Wild

Provide real-world examples of natural selection in action, highlighting specific species and adaptations that have evolved due to natural selection.

Comparative Anatomy and Homology

Discuss the concept of comparative anatomy and homology as evidence for evolution through natural selection, focusing on shared anatomical features among different species.

Adaptive Radiation and Speciation

Explore the process of adaptive radiation and how it leads to speciation, using examples from the natural world to illustrate this phenomenon.

The Role of Genetic Variation

Analyze the importance of genetic variation in the context of natural selection, including how mutations and genetic diversity contribute to evolutionary change.

Sexual Selection and Mate Choice

Examine the concept of sexual selection and how it influences the evolution of traits related to mating and reproduction in various species.

Human Evolution and Natural Selection

Discuss the application of natural selection in human evolution, including adaptations and traits that have shaped the human species.

Ecological Factors and Natural Selection

Analyze how ecological factors, such as competition for resources and environmental changes, drive natural selection and influence the evolution of species.

Evidence from Fossil Records

Examine the evidence for evolution and natural selection found in the fossil record, including transitional fossils and the documentation of evolutionary history.

The Role of Geographic Isolation

Discuss how geographic isolation and allopatric speciation contribute to the diversification of species and the formation of new ones.

Natural Selection Lab Report

Darwins four components of natural selection, made-to-order essay as fast as you need it.

Each essay is customized to cater to your unique preferences

+ experts online

Darwinism and Social Darwinism

Darwin’s reactions to evolution by natural selection, evolution according to natural selection, the role of natural selection in darwin’s theory of evolution, let us write you an essay from scratch.

• 450+ experts on 30 subjects ready to help
• Custom essay delivered in as few as 3 hours

Theory of Natural Selection and Darwin’s Ideas of Evolution

Natural selection and artificial selection in dogs, sexual selection as an another form of natural selection, natural selection: survival of the fittest, get a personalized essay in under 3 hours.

Expert-written essays crafted with your exact needs in mind

Understanding Evolution: Vestigial Structures

Malthus and darwin: a study of theories and their adaptation, darwin’s design: social theory in origin of species, staff selection commission, how natural selection works: a closer look at emperor penguins, relevant topics.

• Mathematics in Everyday Life
• Stephen Hawking
• Time Travel
• Charles Darwin
• Space Exploration
• Engineering

By clicking “Check Writers’ Offers”, you agree to our terms of service and privacy policy . We’ll occasionally send you promo and account related email

No need to pay just yet!

We use cookies to personalyze your web-site experience. By continuing we’ll assume you board with our cookie policy .

• Instructions Followed To The Letter
• Deadlines Met At Every Stage
• Unique And Plagiarism Free

The findings could help researchers understand why some individuals are more vulnerable to deadly Chagas disease.

natural selection

Natural selection of academic papers

• Published: 22 June 2010
• Volume 85 , pages 553–559, ( 2010 )

Cite this article

• Pandelis Perakakis 1 ,
• Michael Taylor 2 ,
• Marco Mazza 3 &
• Varvara Trachana 4  

713 Accesses

16 Citations

14 Altmetric

Explore all metrics

Academic papers, like genes, code for ideas or technological innovations that structure and transform the scientific organism and consequently the society at large. Genes are subject to the process of natural selection which ensures that only the fittest survive and contribute to the phenotype of the organism. The process of selection of academic papers, however, is far from natural. Commercial for-profit publishing houses have taken control over the evaluation and access to scientific information with serious consequences for the dissemination and advancement of knowledge. Academic authors and librarians are reacting by developing an alternative publishing system based on free-access journals and self-archiving in institutional repositories and global disciplinary libraries. Despite the emergence of such trends, the journal monopoly, rather than the scientific community, is still in control of selecting papers and setting academic standards. Here we propose a dynamical and transparent peer review process, which we believe will accelerate the transition to a fully open and free-for-all science that will allow the natural selection of the fittest ideas.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price includes VAT (Russian Federation)

Instant access to the full article PDF.

Rent this article via DeepDyve

Institutional subscriptions

Similar content being viewed by others

How to design bibliometric research: an overview and a framework proposal

Literature reviews as independent studies: guidelines for academic practice

Open peer review: promoting transparency in open science

Bergstrom, C. T., & Bergstrom, T. C. (2004). The costs and benefits of library site licenses to academic journals. Proceedings of the National Academy of Sciences, 101 (3):897–902.

Article   Google Scholar  

Buela-Casal, G., Perakakis, P., Taylor, M., & Checa, P. (2006). Measuring internationality: Reflections and perspectives on academic journals. Scientometrics, 67 (1):45–65.

Chan, L., Kirsop, B., & Arunachalam, S. (2006). Open access archiving: The fast track to building research capacity in developing countries. Science and Development Network , 1.

Dawkins, R. (2006). The selfish gene . NY, USA: Oxford University Press.

Google Scholar  

Directory of open access journals (DOAJ). (2009). http://www.doaj.org . Accessed 3 June.

Harnad, S., Brody, T., Vallières, F., Carr, L., Hitchcock, S., Gingras, Y. et al. (2008). The access/impact problem and the green and gold roads to open access: An update. Serials Review , 34 (1):36–40.

Plotkin, N. (2009). MIT will publish all faculty articles free in online repository. http://tech.mit.edu/V129/N14/open\_access.html . Accessed 4 July.

Registry of Open Access Repositories (ROAR). (2009). http://roar.eprints.org/ . Accessed 3 June.

Romeostats. (2009). Journal policies—summary statistics so far. http://romeo.eprints.org/stats.php . Accessed 3 June.

Taylor, M., Perakakis, P., & Trachana, V. (2008). The siege of science. Ethics in Science and Environmental Politics (ESEP), 8 (1), 17–40.

Thomson. Journal Citation Reports. http://thomsonreuters.com/products_services/scientific/Journal\_Citation\_Reports . Accessed 3 June 2009.

Van Orsdel, L. C., & Born, K. (2008). Periodicals price survey 2008 embracing openness. Library Journal, 133 (7), 6.

Download references

Author information

Authors and affiliations.

Department of Psychology, University of Granada, Campus Cartuja, 18071, Granada, Spain

Pandelis Perakakis

Institute for Space Applications and Remote Sensing (ISARS), National Observatory of Athens (NOA), Vas. Pavlou & I. Metaxa, 15236, Penteli, Greece

Michael Taylor

Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Straße des 17. Juni 135, 10623, Berlin, Germany

Marco Mazza

Institute of Biological Research and Biotechnology (IBRB), National Hellenic Research Foundation (NHRF), 48 Vas. Constantinou Ave., 11635, Athens, Greece

Varvara Trachana

You can also search for this author in PubMed   Google Scholar

Corresponding author

Correspondence to Pandelis Perakakis .

Rights and permissions

Reprints and permissions

About this article

Perakakis, P., Taylor, M., Mazza, M. et al. Natural selection of academic papers. Scientometrics 85 , 553–559 (2010). https://doi.org/10.1007/s11192-010-0253-1

Download citation

Received : 16 December 2009

Published : 22 June 2010

Issue Date : November 2010

DOI : https://doi.org/10.1007/s11192-010-0253-1

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

• Academic publishing
• Peer review
• Find a journal
• Publish with us
• Track your research

Natural selection

Natural selection is the phrase Charles Darwin used in 1859 for the process he proposed to explain the origin of species and their apparent adaptation to their environment.

• Evolutionary Biology
• Biochemistry Research
• Charles Darwin
• The evolution of human intelligence
• Introduction to genetics
• Gregor Mendel

Fossils & Ruins News

Latest headlines.

• Extinct Saber-Toothed Cat On Texas Coast
• Historic Iceberg Surges
• A New Dinosaur from Zimbabwe
• Measuring Embryo Development
• A Unified Account of Darwinism's Varieties
• How Killifish Embryos Survive 8 Month Drought
• Fossil Porcupine in a Prickly Dilemma
• New Kind of Volcanic Eruption
• Recurring Evolutionary Changes in Insects
• Elephant Hunting in Chile 12,000 Years Ago
• Some Black Holes Survive in Globular Clusters
• People Altering Decomposition in Waterways
• Food Groups Based On Level of Processing
• Computer Vision, Machine Learning Aid Driving
• Most Distant Known Galaxy
• The Case of the Missing Black Holes
• Menstrual Periods Arriving Earlier

Trending Topics

Strange & offbeat stories.

How the freshly selected regional centres will bolster the implementation of the Biodiversity Plan

At the fourth meeting of the Subsidiary Body on Implementation (SBI 4) of the Convention on Biological Diversity (CBD), the Parties selected 18 regional organizations spanning the globe in a multilateral push to bolster the implementation of the Kunming-Montreal Global Biodiversity Framework, also known as the Biodiversity Plan , through science, technology and innovation:

• Africa: The Central African Forest Commission (COMIFAC), the Ecological Monitoring Center (CSE), the Regional Centre for Mapping of Resources for Development (RCMRD), the Sahara and Sahel Observatory (OSS), and the South African National Biodiversity Institute (SANBI).
• Americas: The Alexander von Humboldt Biological Resources Research Institute, the Secretariat of the Caribbean Community (CARICOM), and the Central American Commission on Environment and Development (CCAD).
• Asia: ASEAN Centre for Biodiversity (ACB); IUCN Asia Regional Office; IUCN Regional Office for West Asia (ROWA); Nanjing Institute of Environmental Sciences (NIES); Regional Environmental Centre for Central Asia (CAREC).
• Europe: European Commission - Joint Research Centre of the European Commission (JRC); IUCN Centre for Mediterranean Cooperation; IUCN Regional Office for Eastern Europe and Central Asia (ECARO); Royal Belgian Institute for Natural Sciences (RBINS).
• Oceania: The Secretariat of the Pacific Regional Environment Programme (SPREP).

Here are five facts about the selection of these centres and the way they will bring the Parties to the CBD closer to halting and reversing biodiversity loss by 2030 :

1. Nested in existing institutions for efficiency and rapid deployment

The selected centres are hosted by existing institutions that have responded to the CBD Secretariat’s call for expression of interest. The applications received translate a global commitment to implementing the Biodiversity Plan. This global network of centres forms part of the technical and scientific cooperation mechanism under the CBD. They will contribute to filling gaps in international cooperation and catering to the needs of countries in the regions that they cover.

2. One-stop-shop for scientific, technical and technological support

The mandate of the centres is to catalyse technical and scientific cooperation among the Parties to the Convention in the geographical regions they cover. The support they offer may include the sharing of scientific knowledge, data, expertise, resources, technologies, including indigenous and traditional technologies, and technical know-how with relevance to the national implementation of the 23 targets of the Biodiversity Plan. Other forms of capacity building and development may also be provided.

3. Complementarity with existing initiatives

The expected contributions of the centres will constitute a surge of capacity, complementing small-scale initiatives for technical and scientific cooperation among its Parties through programmes such as the Bio-Bridge Initiative . The newly selected centres will expand, scale-up and accelerate efforts in support of the implementation of the Biodiversity Plan.

4. Delivering field support tailored to regional specificities

Countries around the world face well recognized challenges in aligning with universally agreed targets while considering biophysical specificities and national circumstances. The regional centres will provide regionally appropriate solutions.

5. Building on and amplifying existing cooperation

Many examples around the world demonstrate the benefits of transboundary cooperation. In South Africa, the “Black Mambas” Anti-Poaching Unit has benefited from Dutch expertise in fitting rhinoceros with subcutaneous sensors and horn transmitters to track their movements across the Greater Kruger National Park.

On the other side of the Atlantic Ocean, non-governmental organization Corales de Paz (Colombia) shared their “Caribbean Reef Check” methodology and “Reef Repair Diver “programs with Ecuador-based CONMAR. Participants in CONMAR-organized training camps could thus benefit from expertise in coral reef monitoring and coral gardening.

The newly selected centres will seek to expand this constellation of bright spots of cooperation for nature and for people.