Of the fourteen chapters which make up the book no fewer than nine are devoted to proving that evolution has occurred. It has been truly said, that for every one fact biologists have found in support of the special theory of natural selection they have found ten facts supporting the doctrine of evolution. Darwin, then, was in the position of a skilled barrister who has a plausible case and who knows the ins and outs of his brief, while his opponents stood in the shoes of inexperienced counsel who had but recently received their brief, and who had not had the time to master the details thereof. In such circumstances it is not difficult to predict which way the verdict of the jury will go.
Darwin, moreover, had a charming personality. Never was a man with a theory less dogmatic. Never was the holder of a theory more careful of the expressions he used. Never was a scientific man more ready to give ear to his opponents, to meet them half way, and, where necessary, to compromise. Darwin was not afraid of facts, and was always ready to alter his views when they appeared to be opposed to facts. The average scientific man of to-day makes facts fit his theory; if they refuse to fit it he ignores or denies them.
Darwin continually modified his views; when he found himself in a tight place he did not hesitate to resort to Lamarckian factors, such as the inheritance of the effects of use and disuse and of the effects of environment. He conceded that natural selection was insufficient to account for all the phenomena of organic evolution, and advanced the theory of sexual selection in order to account for facts which the major hypothesis seemed to him incapable of explaining.
Darwin, moreover, having ample private means, was not obliged to work for a living, and was therefore able to devote the whole of his time to research. The advantages of such a position cannot be over-estimated, and, perhaps, have not been sufficiently taken into account in apportioning the praise between Darwin and Wallace for their great discovery.
Huxley
To all these factors in Darwin’s favour we must add his good fortune in possessing so able a lieutenant as Huxley.
Huxley was an ardent evolutionist, an able writer, and a brilliant debater. A man of his mental calibre was able, like a clever barrister, to make out a plausible case for any theory which he chose to take up. While nominally a strong supporter of the Darwinian theory, he was in reality fighting for the doctrine of descent. Had any plausible theory of evolution been enunciated, Huxley would undoubtedly have fought for it equally earnestly.
A firm believer in evolution, Huxley was, as Professor Poulton says, confronted by two difficulties,—first, the insufficiency of the evidence of evolution, and, secondly, the absence of any explanation of how the phenomenon had occurred. The Origin of Species solved both these difficulties. It adduced much weighty evidence in favour of evolution, and suggested a modus operandi. Small wonder, then, that Huxley became a champion of Darwinism. But, as Poulton writes, on page 202 of Essays on Evolution, “while natural selection thus enabled Huxley freely to accept evolution, he was by no means fully satisfied with it.” “He never committed himself to a full belief in natural selection, and even contemplated the possibility of its ultimate disappearance.” To use Huxley’s own words: “Whether the particular shape which the doctrine of evolution, as applied to the organic world, took in Darwin’s hands, would prove to be final or not, was, to me, a matter of indifference.”
The result of the fortuitous combination of the circumstances which we have set forth was that in a surprisingly short time the theory of natural selection came to be regarded as a law of nature on a par with the laws of gravitation. Thus, paradoxical though it seems, practical certainty was given to a hitherto uncertain doctrine by the addition of a still more uncertain theory.
“At once,” writes Waggett, “the theory of development leapt from the position of an obscure guess to that of a fully-equipped theory and almost a certainty.”