Natural selection d that Darwin was simply refining Darwin was thoroughly familiar with is theory all those years, although variation in domesticated animals and here is little evidence he altered his began On the Origin of Species with a initial manuscript in all that time detailed discussion of pigeon breeding He knew that breeders selected certain Wallace has the same idea varieties of pigeons and other animals, such as dogs, to produce certain char- The stimulus that finally brought Dar acteristics, a process Darwin called ar- wins theory into print was an essay he tificial selection. Once this had been received in 1858. A young English nat done. the animals would breed true for uralist named Alfred russel walla the characteristics that had been select (1823-1913)sent the essay to Darwin d darwin had also observed that the from Malaysia; it concisely set forth differences purposely developed be he theory of evolution by means of tween domesticated races or breeds natural selection, a theory Wallace had were often greater than those that sep developed independently of Darwin arated wild species. Domestic pigeon Like darwin. wallace had been breeds, for example, show much reatly influenced by Malthus's 1798 greater variety than all of the hundreds essay. Colleagues of Wallace, knowin of wild species of ns four of Darwins work, encouraged him to throughout the world. Such relation- communicate with Darwin. After re ships suggested to Darwin that evolu ceiving Wallace's essay, Darwin ar- ionary change could occur in nature ranged for a joint presentation of their ideas at a seminar in London darwin ing the breeders role in selecting the unsympathetically, as in this drawing from written so long ago, and submitted it next generation-a process Darwin an 1874 publication. for publication called natural selection Darwins theory thus incorporates the hypothesis of evolution, the pro- cess of natural selection. and the mass of new evidence Publication of darwin's the for both evolution and natural selection that Darwin Darwins book appeared in November 1859 and caused an ompiled. Thus, Darwins theory provides a simple and immediate sensation. Many people were deeply disturbed by direct explanation of biological diversity, or why animals the suggestion that human beings were descended from the are different in different places: because habitats differ in same ancestor as apes(figure 1.11). Darwin did not actually their requirements and opportunities, the organisms with discuss this idea in his book, but it followed directly from the characteristics favored locally by natural selection will principles he outlined. In a subsequent book, The Descent of tend to vary in different places Man, Darwin presented the argument directly, building a powerful case that humans and living apes have common an- cestors. Although people had long accepted that humans Darwin Drafts His Argument closely resembled apes in many characteristics, the possibility that there might be a direct evolutionary relationship was un- Darwin drafted the overall argument for evolution by natu- acceptable to many. Darwins arguments for the theory of ral selection in a preliminary manuscript in 1842. After evolution by natural selection were so compelling, howe friends, however, Darwin put it in a drawer, and for tellectual community of Great Britain after the 1860s 16 years turned to other research. No one knows for sure why Darwin did not publish his initial manuscript-it is The fact that populations do not really expand very thorough and outlines his ideas in detail. Some histo- geometrically implies that nature acts to limit rians have suggested that Darwin was shy of igniting public population numbers. The traits of organisms tha criticism of his evolutionary ideas-there could have been survive to produce more offspring will be more little doubt in his mind that his theory of evolution by nat- common in future generations-a process Darwin ural selection would spark controversy. Others have pro called natural selection 14 Part I The Origin of living thingsNatural Selection Darwin was thoroughly familiar with variation in domesticated animals and began On the Origin of Species with a detailed discussion of pigeon breeding. He knew that breeders selected certain varieties of pigeons and other animals, such as dogs, to produce certain char￾acteristics, a process Darwin called ar￾tificial selection. Once this had been done, the animals would breed true for the characteristics that had been select￾ed. Darwin had also observed that the differences purposely developed be￾tween domesticated races or breeds were often greater than those that sep￾arated wild species. Domestic pigeon breeds, for example, show much greater variety than all of the hundreds of wild species of pigeons found throughout the world. Such relation￾ships suggested to Darwin that evolu￾tionary change could occur in nature too. Surely if pigeon breeders could foster such variation by “artificial selec￾tion,” nature could do the same, play￾ing the breeder’s role in selecting the next generation—a process Darwin called natural selection. Darwin’s theory thus incorporates the hypothesis of evolution, the pro￾cess of natural selection, and the mass of new evidence for both evolution and natural selection that Darwin compiled. Thus, Darwin’s theory provides a simple and direct explanation of biological diversity, or why animals are different in different places: because habitats differ in their requirements and opportunities, the organisms with characteristics favored locally by natural selection will tend to vary in different places. Darwin Drafts His Argument Darwin drafted the overall argument for evolution by natu￾ral selection in a preliminary manuscript in 1842. After showing the manuscript to a few of his closest scientific friends, however, Darwin put it in a drawer, and for 16 years turned to other research. No one knows for sure why Darwin did not publish his initial manuscript—it is very thorough and outlines his ideas in detail. Some histo￾rians have suggested that Darwin was shy of igniting public criticism of his evolutionary ideas—there could have been little doubt in his mind that his theory of evolution by nat￾ural selection would spark controversy. Others have pro￾posed that Darwin was simply refining his theory all those years, although there is little evidence he altered his initial manuscript in all that time. Wallace Has the Same Idea The stimulus that finally brought Dar￾win’s theory into print was an essay he received in 1858. A young English nat￾uralist named Alfred Russel Wallace (1823–1913) sent the essay to Darwin from Malaysia; it concisely set forth the theory of evolution by means of natural selection, a theory Wallace had developed independently of Darwin. Like Darwin, Wallace had been greatly influenced by Malthus’s 1798 essay. Colleagues of Wallace, knowing of Darwin’s work, encouraged him to communicate with Darwin. After re￾ceiving Wallace’s essay, Darwin ar￾ranged for a joint presentation of their ideas at a seminar in London. Darwin then completed his own book, expand￾ing the 1842 manuscript which he had written so long ago, and submitted it for publication. Publication of Darwin’s Theory Darwin’s book appeared in November 1859 and caused an immediate sensation. Many people were deeply disturbed by the suggestion that human beings were descended from the same ancestor as apes (figure 1.11). Darwin did not actually discuss this idea in his book, but it followed directly from the principles he outlined. In a subsequent book, The Descent of Man, Darwin presented the argument directly, building a powerful case that humans and living apes have common an￾cestors. Although people had long accepted that humans closely resembled apes in many characteristics, the possibility that there might be a direct evolutionary relationship was un￾acceptable to many. Darwin’s arguments for the theory of evolution by natural selection were so compelling, however, that his views were almost completely accepted within the in￾tellectual community of Great Britain after the 1860s. The fact that populations do not really expand geometrically implies that nature acts to limit population numbers. The traits of organisms that survive to produce more offspring will be more common in future generations—a process Darwin called natural selection. 14 Part I The Origin of Living Things FIGURE 1.11 Darwin greets his monkey ancestor. In his time, Darwin was often portrayed unsympathetically, as in this drawing from an 1874 publication