THE GROWTH OF WALLACE’S CONVICTIONS ON EVOLUTION AND DISCOVERY OF NATURAL SELECTION--BORNEO 1855--TERNATE 1858.
We have already seen in the earlier part of this volume, the gradual development of the theory of Natural Selection in the mind of Darwin, and the long succession of experiments and observations which he undertook before he could bring himself to publish anything upon the subject, as well as the conditions which forced him to a hurried publication in the end. It is of the deepest interest to compare with this the account which Wallace has given us of the mental process by which he arrived at the same conclusions.
This deeply interesting personal history has only been known during the last few years; in 1891 Wallace republished his “Essays on Natural Selection” in one volume, combined with “Tropical Nature,” and he has added (on pp. 20, 21) the following introductory note to Chapter II., viz. the reprint of his Linnean Society Memoir “On the Tendencies of Varieties to depart indefinitely from the Original Type.” The note is here reprinted in full:--
“As this chapter sets forth the main features of a theory identical with that discovered by Mr. Darwin many years before but not then published, and as it has thus an historical interest, a few words of personal statement may be permissible. After writing the preceding paper [“On the Law which has Regulated the Introduction of New Species”] the question of _how_ changes of species could have been brought about was rarely out of my mind, but no satisfactory conclusion was reached till February 1858. At that time I was suffering from a rather severe attack of intermittent fever at Ternate in the Moluccas, and one day, while lying on my bed during the cold fit, wrapped in blankets, though the thermometer was at 88° Fahr., the problem again presented itself to me, and something led me to think of the ‘positive checks’ described by Malthus in his ‘Essay on Population,’ a work I had read several years before, and which had made a deep and permanent impression on my mind. These checks--war, disease, famine and the like--must, it occurred to me, act on animals as well as man. Then I thought of the enormously rapid multiplication of animals, causing these checks to be much more effective in them than in the case of man; and while pondering vaguely on this fact there suddenly flashed upon me the _idea_ of the survival of the fittest--that the individuals removed by these checks must be on the whole inferior to those that survived. In the two hours that elapsed before my ague fit was over I had thought out almost the whole of the theory, and the same evening I sketched the draft of my paper, and in the two succeeding evenings wrote it out in full, and sent it by the next post to Mr. Darwin. Up to this time the only letters I had received from him were those printed in the second volume of his _Life and Letters_ (vol. ii., pp. 95 and 108), in which he speaks of its being the twentieth year since he ‘opened his first note-book on the question how and what way do species and varieties differ from each other,’ and after referring to oceanic islands, the means of distribution of land-shells, &c., added: ‘My work, on which I have now been at work more or less for twenty years, _will not fix or settle anything_; but I hope it will aid by giving a large collection of facts, with one definite end.’ The words I have italicised, and the whole tone of his letters, led me to conclude that he had arrived at no definite view as to the origin of species, and I fully anticipated that my theory would be new to him, because it seemed to me to settle a great deal. The immediate result of my paper was that Darwin was induced at once to prepare for publication his book on the _Origin of Species_ in the condensed form in which it appeared, instead of waiting an indefinite number of years to complete a work on a much larger scale which he had partly written, but which in all probability would not have carried conviction to so many persons in so short a time. I feel much satisfaction in having thus aided in bringing about the publication of this celebrated book, and with the ample recognition by Darwin himself of my independent discovery of ‘natural selection.’ (See _Origin of Species_, 6th ed., introduction, p. 1, and Life and Letters, vol. ii, chap. iv., pp. 115–129 and 145).”