The Origin of Species

Virtually everyone knows the story of the writing of The Origin of Species: the voyage on the Beagle, the coincidence of Darwin’s and Wallace’s views on evolution, the great stir Darwin’s book created, and Darwin’s subsequent problems and doubts. These issues are left aside here to concentrate on some of Darwin’s statements about classification of plants and animals. Here his views contrast starkly with those of his predecessors and with those of many of his supposed followers as well.

The very title bears close scrutiny: The Origin of Species by Means of Natural Selection; Or the Preservation of Favoured Races in the Struggle for Life. The book is about the origin (in the sense of productive principle and genealogy), not the character, behavior, morphology, or embryology of species. It is about the origin of species, that is, how the categories of living things in the world of observation have come into existence—a process until then explained by the idea of special creation, which organized species into a chain of being, the species then being acted upon by humoral/environmental forces. The term “natural selection” is used because the causal agent in spéciation is not God or any other supernatural principle that at some time in the remote past created eternal categories; it is the continuous operation of blind material laws.

The restatement of the subject—Or the Preservation of Favoured Races in the Struggle for Life—brings up an ambiguity that runs through Darwin’s work and that of most other nineteenth-century thinkers: the terms “species” and “race” are often used interchangeably. In Darwin’s case, the use of the term “race” is important because in ordinary speech “race” conveys a strong sense that genealogical principles are the primary ones that give rise to and define species boundaries. Species are separate categories of things in the world. To call them races is to emphasize the genealogical lines stretching from past to present and set the scene for the idea of descent with modification.

The “struggle for life” notion points to reproductive competion under specific environmental conditions as the mechanism by which natural selection operates. It is not a providential hand that chooses but blind physical laws, and the struggle never ends. Thus Darwin titled his book well, for the title summarizes his theory.

The book itself, despite Darwin’s continual reference to it as an essay written in haste, has a coherent internal structure that supports the argument well. It is divided into three major serions, each dealing with a specific set of issues.

The first section is devoted to an exposition of the mechanisms that produce variation, competition, and ultimately spéciation by means of natural selection. Darwin begins this section strategically by discussing variation under domestication. Since humans have induced spéciation quite often by manipulating the environments and reproduction of plants and animals, how can we believe that species boundaries are absolute and fixed? Darwin also points out that species under domestication are highly variable. It is this variability that permits us to breed plants and animals as we do.

Variation is the centerpiece of Darwin’s world view, and thus he begins with it. Where others saw uniformity and clear-cut species boundaries, Darwin saw ranges of variation. Much of his observational life was spent in cataloguing variation, a phenomenon that not only was theoretically important for him but clearly fascinated him in its own right. This focus contrasts sharply with the pre- and non-evolutionary views of the world, in which fixed natural categories of things succeed themselves from generation to generation, with no change other than some preordained progress or fateful degeneration.

Having made his argument about variation and selection in the world of everyday human experience, Darwin then moves outward to the undomesticated world, showing that a similarly great amount of variation exists in all living things. Examples abound, drawn from everywhere. Variation is the first step in the argument for evolution.

Darwin then introduces the “struggle for life.” Outside the domesticated world there are no plant and animal breeders to act on variation. Darwin argues that different variants are differentially capable of reproducing successfully in the diverse environments in which they are found. Those better able to reproduce proliferate and the others fade away. This view is complemented by the naming and development of the concept of natural selection.

In Chapter 1, humans were the selectors. Now Darwin opens up the possibility that blind natural forces act as selectors on the immense number of variants among plants and animals. This process of natural selection gradually changes the structure of species of plants and animals until new and different species come into existence, all genealogically linked to their predecessors. He closes the section with a chapter on “laws of variation,” in which he claims that a theory based on variation and natural selection will yield a coherent interpretation of the history of life on earth.

The second section strategically poses the major objections that could be advanced to compromise his general argument. Here Darwin’s capabilities as a scientific thinker become particularly manifest as he first conceptualizes the opposing views and then systematically under-cuts them. He casts down the gauntlet in scientific fashion: this is the theory; here are all the objections to it; none of the objections is crippling, so until an unanswerable objection can be formulated, the theory stands.

In the third section Darwin arrays geological, geographical, and morphological evidence in support of the theory of evolution. With each body of evidence goes the suggestion that much more evidence could be adduced. The recapitulation of the whole argument at the end of the book shows, among other things, just how well planned this “essay” was. Throughout the book the movement is measured and self-conscious: argument, counterargument, proof, recapitulation.

Often using little and tenuous evidence, Darwin succeeded in making a forceful argument that species arise continuously by material processes, thereby demolishing the centerpiece of the pre-evolutionary views of nature. Darwin did not create an unrecognizable world of nature. Rather he took the world of nature as people observed it and explained its structure in a way that was odious to a significant part of his audience.

It is helpful to flesh out the argument about evolutionary classification put forward here with some of Darwin’s specific statements. The Origin of Species begins with a criticism of the view of species as immutable and separate:

An emphasis on genealogical relationships (what Darwin called “true generation”) is the key to his argument against separate creation. Occasionally this emphasis on genealogical relationships leads him to appeal to the old language of “blood,” as in the following case: “… looking to the domestic dogs of the whole world, I have… come to the conclusion that several wild species of Canidae have been tamed, and that their blood, in some cases mingled together, flows in the veins of our domestic breeds” (p. 39). He contradicts the notion of separately created species by conjuring up genealogical relations between wild and domesticated dogs. If such genealogical relations exist, and the wild comes before and gives rise to the tame, then species are generated out of each other.

Later Darwin links variation with spéciation, in this case by speaking of domesticated species: “The key is man’s power of accumulative selection: nature gives successive variations; man adds them up in certain directions useful to him. In this sense he may be said to have made for himself useful breeds” (p. 48).

This is a frontal attack on special creation. Nature itself is the producer of variation. In the pre-evolutionary view, nature merely reflected the initial order made by the creator. Humans produce species by acting on this variation; humans “create” species through selection. Such actions would be impossible in a world of hermetically sealed separate species. For Darwin, variation is not deviation from the ideal form of the species; it is the source of all species.

Darwin sums up this argument by stating:

Thus by the end of his initial chapter Darwin has put most of the major elements of his argument into play. Beginning with the world of everyday observations of domesticated plants and animals and their variations, he moves outward toward larger principles. If humans, by controlling reproduction, can create species by selecting for certain variants, then species are not immutable. It is then conceivable that other agencies (such as the environment) could also select among the variants within an existing species and ultimtely cause the creation of new species. If this argument is accepted, separate creation and the chain of being disappear.

The central obstacle left for Darwin to overcome is the proof that variation and selection occur outside of the domesticated species directly subject to human agency. He turns to this task with vigor.

The argument begins with a strong emphasis on the arbitrariness of species boundaries. Darwin states: “… I was much struck how entirely vague and arbitrary is the distinction between species and varieties” (p. 63). Then he elaborates the argument:

Darwin’s view of the empirical world centers on variability, complexity, and classificatory ambiguity. He radically reverses the view of nature as a linked chain of sharply separable species with no motion other than self-replication. In place of fixed species Darwin inserts “an insensible series.” In place of clear categories he interjects the arbitrariness of species boundaries. And in place of a series of similar but variant organisms he poses a historical, evolutionary relationship.

To counter the existing view of the natural world, Darwin attacked the dominant classificatory scheme. Rather than seeing species as eternal categories that empirically vary around the perfect expression of the species’ inherent character, he makes variation the real and eternal feature of nature, converting species into momentary historical embodiments of these variations. In this massive reversal he subverts special creation and the chain of being at the same time. He creates a view a nature that is the opposite of the dominant one.

This argument logically leads him to the next questions: What agency causes the appearance of various species out of the multiplicity of variation observed in nature? Why is nature simply not an incoherent teeming of life? Many thinkers have attempted to reinsert the hand of God into the theory of evolution at this point by arguing that the whole process of variation and selection is providentially guided. Darwin did not take this path. Instead he insisted that the origin of species must be understood solely as a historical process with a beginning, operating according to coherent principles, but without an intrinsic direction or goal.

Defining the struggle for life, he says:

Variation, complexity, multiplicity, and competitive advantage are the centerpieces of Darwin’s view.

Why could God not create such a world? Darwin does not, in fact, dispute the existence of God, but he deeply distrusts human understanding of nature. Darwin’s view of the physical limitations of the human mind and its capacity for experience in relation to the complexity and vastness of the physical universe makes him deeply suspicious of simplistic conceptions of the creator.

By emphasizing the diversity and complexity of the natural world, Darwin stresses a point he makes repeatedly in the Origin and later, in more detail, in The Descent of Man.

Darwin is very careful to argue that natural selection itself does not induce variation. Were he to admit that it did, variation would be easily reduced to a mere incident in natural selection, with evolution following directly from environmental requirements. As it is, his emphasis is just the opposite. There is hugely more variation available in the world than is operated on by selection. Variation is produced by principles that Darwin did not in fact understand, but he was certain that the cause was not the process of selection itself. Living nature’s prime characteristic is production of variation; the production of temporary categories (species) is a subsequent step. The world moves dialectically from variation to selection to variation. Selection creates coherent classes of organisms.

Darwin argues that the crossing of varieties is a law of nature itself. If the chain-of-being argument were correct, then logically the best examples of a species would fertilize themselves. But Darwin’s observations lead him

Reproduction is mixing of variants.

Darwin reverses separate creation by considering the variations to be real and continuous and the species to be only momentary manifestations. He then argues that species breed in such a way as to produce rather than to reduce variation. Thus variation, not the fixity of species, is the “law of nature.”

Darwin has chosen his words well, breaking the old meaning of “law of nature” from its mold as a description of a fixed order. He moves on a chain of rhetorical links from variation to domestication, breeding, and natural selection. At each juncture he challenges others to explain these facts better. Nature is a complex set of processes, a history with no goal. This is what Darwin’s chart of species change emphasizes. (See Figure 2.)

When Darwin discusses the geological record, he strongly states his historical view of nature as in continual motion against the view of nature as consisting of a set of fixed, uniform categories. The constancy in nature is a constancy of motion:

The uniformity of causes imparts order to nature, but these causes work only through time. Each successive moment in the history of life is different from all other moments. This is a direct attack on the standard view of special creation.

Darwin shows his awareness that the issue of classification is the central one in evolutionary theory when he points to “the difficulties which are encountered on the view that classification either gives some unknown plan of creation, or is simply a scheme for enunciating general propositions and of placing together the forms most like each other” (p. 387). He points out that classifications are a complex mix of morphological and functional criteria; that embryological affinities not obvious in adult members of species are important in classifications; and that geographical distributions have also been important. Darwin insists, however, that there is only one correct overarching principle of classification. It must be followed, with all other principles subordinated to its requirements:

Note that he says the arrangement must be “genealogical in order to be natural.” Nature is defined as a historical process, and all classifications that are to aid in clarifying this natural process must be based on historical relationships. Darwin does not deny that classification can be done on numerous grounds, but he does deny that any but a genealogical classification can be used as the basis of an evolutionary analysis.

There is no question that the reaction to The Origin of Species was appropriate. The shock, excitement, and outrage were fully earned by such a frontal attack on the basis of existing views of nature. The Origin is a polemic. Despite its often ponderous apparatus of facts and its flat language, its central structure is provided by a reversal of the Western view of nature, supported by an appeal to scientific appraisal of the “facts,” to the value we attach to the scientific method and rational analysis.

The principal issue he did not attack directly was that of human evolution. The only reference to it is the famous cryptic line “Much light will be thrown on the origin of man and his history” (p. 449). But no one could doubt what Darwin had in mind. If special creation and the chain of being had given humans a privileged place in nature, then a repudiation of those views must also alter the human position. It did, though his full statement of the point was not published until 1871, under the title The Descent of Man and Selection in Relation to Sex.

The Descent of Man and Selection in Relation to Sex

The Descent is a remarkable work both for the currency of its arguments and for the relative obscurity into which it has fallen. While The Origin is available in a variety of popular editions, until 1981 the Descent was for a long time available only in expensive facsimiles. Thus its readership has been quite limited, though the general public has made best-sellers of other books on the same general topic (Lorenz [1963] 1971, Morris 1969, Ardrey 1966).

Evolutionary analysis applied to humans and the theory of sexual selection appear together in the Descent because Darwin believed that natural selection was much relaxed in the human case. In its place, sexual selection, heightened by human cultural capacities for its elaboration, is seen as a prime force. Darwin uses sexual selection to explain, among other things, the phenotypic diversity of human “races.”

At each point in the long argument, humans are shown to be influenced by the same forces that are at work in the rest of the natural world. Thus the Descent closes out the hope that a unique realm of natural laws might be preserved that would maintain the special dignity of human beings.

Darwin emphasizes human variability just as strongly as he emphasized the variability of nonhuman life in the Origin. “The variability or diversity of the mental faculties in men of the same race, not to mention the greater differences between men of distinct races, is so notorious that not a word need here be said. So it is with the lower animals” ([1871] 1974:26).

After making some remarkably contemporary-sounding comments to the effect that humans are like domesticated animals in our variability, in the way selective forces affect us, and in that we are a highly diverse, wide-ranging species, he argues that human superiority is a direct result of our success in the struggle for existence:

After these generalities, Darwin focuses the argument on each of these traits in turn: intellectual faculties, social habits, body structure. Regarding mental faculties he says:

Regarding social living, Darwin argues that social habits and social control depend on the animal’s ability to sense the approval and disapproval of its conspecifics. He calls this capacity “sympathy” and claims that it also evolved by natural selection. All social animals have it, but humans have it in a higher degree. Darwin thus erases the line between human and nonhuman.

In the course of his argument Darwin explores the notion that different environments act as spurs to different kinds of cultural systems, especially the idea that challenging environments stimulate great activity and industriousness. He advances a number of eugenic arguments as ways of seeing natural selection at work on the populations of “civilized” societies, though his position is moderate by comparison with Francis Galton’s hard line ([1869] 1962). According to Darwin, the instinct of sympathy—the instinct to act in accordance with our understanding of the effect our actions will have on other people—is the basis of our social existence. It prohibits us from taking positive eugenic measures against the weak.

After delivering the judgment on the animal affinities and genealogy of humans for which Darwin is so famous, he attempts to replace absolute human superiority with a sense of the majesty of life itself:

When Darwin takes up the vexed question of race, he remains true to his principles. He begins by returning to the general argument that the question of race must be very ambiguous if even species boundaries are fuzzy. He then states that the question whether the races are species or not cannot be solved in the absence of a general definition of species that is accepted by all biologists. Lacking such a definition, he argues that

To account for the great differences among the races, Darwin turns to the principle of sexual selection. He views the development of highly distinctive morphological and behavioral characteristics primarily as means of attracting mates.

The work concludes with the following summary:

The brutality of his last line is stunning. The choice we are left with is to be primitives and believe in special creation or to be civilized and try to make do with evolution and find new sources of species pride.

At the very end the book adopts an uneasy balance between a view of our social obligations to educate people as far as possible (because increasing intellectual awareness necessarily improves moral judgment) and Darwin’s laissez-faire view of society as an arena of free social competition. The book contains many tensions of this sort. There are lapses into racist doctrines; there is a good deal of overt and covert sexism; eugenics is toyed with. Yet by comparison with such contemporaries as Spencer and Galton, Darwin was very cautious on these issues—more ready than they to accept responsibilities for the protection of the weak than to use evolutionary doctrines to justify the suppression of the poor and the defenseless among us, and less willing to derive his ethics from the study of biology.