One hundred fifty-two years ago today, Charles Darwin’s Origin of Species was published. The first print run of 1250 sold out immediately. The second edition of 3000 copies, rushed into print on January 7, 1860, sold out quickly as well. Everyone, it seemed, was reading and discussing the book and its theory. George Eliot wrote a friend that “we have been reading Darwin’s Book…just now: it makes an epoch.”
Darwin had been working on his theory for over twenty-five years, ever since he had returned to England from his voyage on the HMS BEAGLE. He spent much of that time compiling vast amounts of evidence for the theory that species change into new species over time. Darwin was determined that his published theory would satisfy the conditions for good science laid down by John Herschel and William Whewell. In particular, Darwin hoped to show that his theory of evolution by natural selection was consilient, in the sense that it was supported by evidence of many different kinds. In Origin, Darwin showed that his theory provided a causal explanation for facts in the realms of classification of organisms (how they are sorted into groups), biogeography (patterns of distribution of species), comparative anatomy (homologous structures, that is, parts that were similar in different species), paleontology (especially the fossil record, which shows both the extinction of old species and the arrival of new ones) and other areas. Darwin emphasized this appeal to consilience in later editions of the book, arguing that “I cannot believe that a false theory would explain…the several large classes of facts above specified.”
Darwin was pushed into publishing his book by learning that another naturalist, Alfred Russel Wallace, had written a paper on the “introduction” of species that made similar claims about the how patterns in the geographical distribution of species could be explained by the introduction of new species near an already existing, closely related species. The geologist Charles Lyell realized that Wallace’s theory was close to Darwin’s, and urged his friend to publish quickly so as to establish his priority. As Darwin began to work, Wallace sent Darwin a paper describing an evolutionary mechanism similar in some ways to Darwin’s mechanism of natural selection. On July 1, 1858, a two papers by Wallace and Darwin were presented jointly to the Linnean Society. After that, Darwin began writing his book, which he considered an “abstract of my whole work.”
Happy Birthday, Origin of Species, and Happy Thanksgiving!