Since it is not an uncommon error to confound natural selection with evolution, it may be well to point out that, while based on evolution, Darwinism is distinct from it. Evolution is the development of new organisms through heredity, variation, and adaptation. Darwinism, or the doctrine of natural selection, as best defined in these pages by Darwin himself, is seen to involve quite different factors from those of evolution as thus restricted. For candor and childlike simplicity, the writings of Darwin are especially noteworthy among the modest utterances of great men, and nowhere are these qualities more strikingly revealed than in the following account of the production of his principal work.
From September, 1854, I devoted my whole time to arranging my huge pile of notes, to observing, and to experimenting in relation to the transmutation of species. During the voyage of the Beagle I had been deeply impressed by discovering in the pampean formation great fossil animals covered with armor like that on the existing armadillos; secondly, by the manner in which closely allied animals replace one another in proceeding southward over the continent; and thirdly, by the South American character of most of the productions of the Galapagos Archipelago, and more especially by the manner in which they differ slightly on each island of the group, none of the islands appearing to be very ancient, in a geological sense.
It was evident that such facts as these, as well as many others, could be explained only on the supposition that species gradually become modified; and the subject haunted me. But it was equally evident that neither the action of the surrounding conditions nor the will of the organisms (especially in the case of plants) could account for the innumerable cases in which organisms of every kind are beautifully adapted to their habits of life—for instance, a woodpecker or a tree-frog to climb trees, or a seed for dispersal by hooks or plumes. I had always been much struck by such adaptations, and until these could be explained it seemed to me almost useless to endeavor to prove by indirect evidence that species have been modified.
After my return to England it appeared to me that by following the example of Lyell in geology, and by collecting all facts which bore in any way on the variation of animals and plants under domestication and nature, some light might perhaps be thrown on the whole subject. My first note-book was opened in July, 1837. I worked on true Baconian principles, and without any theory collected facts on a wholesale scale, more especially with respect to domesticated productions, by printed inquiries, by conversation with skilful breeders and gardeners, and by extensive reading. When I see the list of books of all kinds which I read and abstracted, including whole series of journals and transactions, I am surprised at my industry. I soon perceived that selection was the keystone of man's success in making useful races of animals and plants. But how selection could be applied to organisms living in a state of nature remained for some time a mystery to me.
In October, 1838, that is, fifteen months after I had begun my systematic inquiry, I happened to read for amusement Malthus's Essay on the Principle of Population, and being well prepared to appreciate the struggle for existence which everywhere goes on, from long-continued observation of the habits of animals and plants, it at once struck me that under these circumstances favorable variations would tend to be preserved, and unfavorable ones to be destroyed. The result of this would be the formation of new species. Here then I had at last got a theory by which to work; but I was so anxious to avoid prejudice that I determined not for some time to write even the briefest sketch of it. In June, 1842, I first allowed myself the satisfaction of writing a very brief abstract of my theory in pencil in thirty-five pages; and this was enlarged during the summer of 1844 into one of two hundred thirty pages, which I had fairly copied out and still possess.
But at that time I overlooked one problem of great importance; and it is astonishing to me, except on the principle of Columbus and his egg, how I could have overlooked it and its solution. This problem is the tendency in organic beings descended from the same stock to diverge in character as they become modified. That they have diverged greatly is obvious from the manner in which species of all kinds can be classed under genera, genera under families, families under sub-orders and so on; and I can remember the very spot in the road, while riding in my carriage, that, to my joy, the solution occurred to me; and this was long after I had come to Down. The solution, as I believe, is that the modified offspring of all dominant and increasing forms tend to become adapted to many and highly diversified places in the economy of nature.
Early in 1856 Lyell advised me to write out my views fully, and I began at once to do so on a scale three or four times as extensive as that which was afterward followed in my Origin of Species; yet it was only an abstract of the materials which I had collected, and I got through about half the work on this scale. But my plans were overthrown, for early in the summer of 1858 Alfred Russel Wallace, who was then in the Malay Archipelago, sent me an essay On the Tendency of Varieties to Depart Indefinitely from the Original Type, and this essay contained exactly the same theory as mine. Mr. Wallace expressed the wish that if I thought well of his essay, I should send it to Lyell for perusal.
The circumstances under which I consented, at the request of Lyell and Hooker, to allow of an abstract from my manuscript, together with a letter to Asa Gray, dated September 5, 1857, to be published at the same time with Wallace's essay, are given in the Journal of the Proceedings of the Linnean Society, 1858. I was at first very unwilling to consent, as I thought Mr. Wallace might consider my doing so unjustifiable, for I did not then know how generous and noble was his disposition. Neither the extract from my manuscript nor the letter to Gray had been intended for publication, and they were badly written. Mr. Wallace's essay, on the other hand, was admirably expressed and quite clear. Nevertheless, our joint productions excited very little attention, and the only published notice of them which I can remember was by Professor Haughton, of Dublin, whose verdict was that all that was new in them was false, and what was true was old. This shows how necessary it is that any new view should be explained at considerable length in order to arouse public attention.
In September, 1858, I set to work by the strong advice of Lyell and Hooker to prepare a volume on the transmutation of species, but was often interrupted by ill-health and short visits to Doctor Lane's delightful hydropathic establishment at Moor Park. I abstracted the manuscript begun on a much larger scale in 1856, and completed the volume on the same reduced scale. It cost me thirteen months and ten days' hard labor. It was published under the title of the Origin of Species, in November, 1859. Though considerably added to and corrected in the later editions, it has remained substantially the same book.
It is no doubt the chief work of my life. It was from the first highly successful. The first small edition of twelve hundred fifty copies was sold on the day of publication, and a second edition of three thousand copies soon afterward. Sixteen thousand copies have now (1876) been sold in England; and considering how stiff a book it is, this is a large number. It has been translated into almost every European tongue, even into such languages as Spanish, Bohemian, Polish, and Russian. It has also, according to Miss Bird, been translated into Japanese, and is much studied in that country. Even an essay on it has appeared in Hebrew, showing that the theory is contained in the Old Testament! The reviews were very numerous; for some time I collected all that appeared on the Origin and on my related books, and these amount (excluding newspaper reviews) to two hundred sixty-five; but after a time I gave up the attempt in despair. Many separate essays and books on the subject have appeared; and in Germany a catalogue, or bibliography, on "Darwinismus" has appeared every year or two.