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By Root 1770 0

Through the course of time, it becomes clear that creatures so selected breed true. In effect, the first chapter lays out the entire process of evolutionary development as the book will describe it in full, although the conditions of artificial breeding cannot, at first, be taken as the literal equivalent to natural selection. But just as breeders, who have been responsible for producing extravagantly different breeds, cannot any longer believe that those breeds descended from a single species, so the society into which Darwin wrote could not believe that the extraordinary variety of organisms in nature had descended from one or few species.

Evolution, then, requires variation, and Darwin presents more than sufficient evidence (in certain respects this was always uncontroversial) that organisms produce variations with great frequency, although most variations—unselected, or, perhaps more important, useless in aiding survival and reproduction—are lost. Variations in domestic animals are perpetuated only when breeders “select” them. Darwin did not, and could not at that time, know what it is that produces variations—he speaks often of the “unknown laws of variation.” It was sufficient for his argument that variations were frequent and could be inherited. “The key,” he argued, “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 make for himself useful breeds” (p. 35).

Many of Darwin’s colleagues, particularly A. R. Wallace, who was the codiscoverer of “natural selection,” insisted that domestic selection had nothing whatever to do with natural selection. Having demonstrated that domestic animals produced variations and that humans could select variations for inheritance, Darwin still had to prove that these conditions existed in nature, that “nature gives successive variations” not only to domestic animals but to wild ones, and that nature could somehow do the work that conscious human selectors did in domestic conditions. The next two chapters are devoted to these problems. Do variations appear in nature as well? And if so, how can they possibly be inherited without an intelligent selector pairing animals with similar variations? And since organisms are already well adapted to their environments, wouldn’t any variations make them less likely to succeed in nature and therefore damage their ability to reproduce successfully? Without explanations of these problems, Darwin would have had to slide over into Paley’s camp after all, for he, like Paley, recognized immediately the extraordinary adaptations with which organisms maneuvered through their environments, and the immediate inference of intelligent design would have seemed inescapable. The special power of Darwin’s simple argument is that the variations’ effect on the fitness of the organism determines its success. The fineness of adaptation is the result of accumulated variations through the extensive periods of geological time that Lyell had in effect given Darwin. (To this day, despite a century and a half of accumulated evidence and successful science, there are many—although for the most part they are all previously committed to something like fundamentalist religion—who insist that intelligent design is the only possible explanation of fine adaptations.)

In “Variation under Nature” Darwin discusses at length problems of classification, but the central point is that “individual differences” are common: “No one supposes that all the individuals of the same species are cast in the very same mould” (p. 47), and these individual differences “afford materials for natural selection.” Here is a point at which Darwin’s focus on the aberrant individuals of a species figures prominently in the development of his theory. “Systematists,” he points out, “are far from pleased at finding variability in important characters” (p. 47). Darwin, on the other hand, seeks it out and finds it—virtually everywhere. Taxonomists seek those points on which different organisms resemble