Whereas many people readily accepted the idea of evolution, perhaps because the concept had been discussed by biologists at least since 1809, when Lamarck published his book Philosophic Zoologique, and in England since 1844, when the book, Vestiges of the Natural History of Creation, was published anonymously by Robert Chambers, many remained sceptical about the mechanism proposed by Darwin. Already after the first reading of the book, at the end of 1859, Darwin's faithful "bulldog", T.H. Huxley, pointed out that the accumulation of small variations constituted a serious problem, not the least because the existence of inheritable variations with large effects were known. In a review of the book he mentioned two instances of this kind, hexadactyly in humans and short- leggedness in the "ancon sheep". He even declared that he was not sure that Darwin's method was correct.
This critique was taken up by many quarters, and in 1872 Mivart published the book The Genesis of Species which attempted to show that there are many examples of changes of animals properties, which we may be sure have occurred, and which could not possibly have originated through the accumulation of small variations, because they represented typical either-or situations.
Ellegard has studied the English periodical press during the years 1859-1872 in order to estimate the reception of Darwin's work. As it turned out, the idea about evolution proper was readily accepted, but natural selection was rejected almost ''unanimously. And he concludes that no doubt Mivart's book had contributed essentially to this negative attitude.
In fact, the opposition continued during the rest of the century and the first decades of the present one. It seems that the change of opinion was the result of some mathematicians, and some biologists who were clever mathematicians, suggesting that what had failed to substantiate the mechanism of accumulation through selection, was that Mendel's theory of paniculate inheritance, unknown to Darwin, had not been incorporated. When this was done, they showed that it was possible to account for evolution in mathematical terms.
The reversion to the belief in Darwinism, soon to be called "neo-Darwinism", was a very fast event: most of the scientific world was converted in less than two decades, which is a very short time for a new theory to become established. It is difficult to understand the reason, for everybody was aware of certain features that would be hard, or even impossible, to achieve through the accumulation of small variations. Only a very superficial acquaintance with ontogenetic development and epigenetic mechanisms could apparently explain the conversion.
But perhaps there was a completely different reason too. namely that the founders of neo-Darwinism claimed that the study of evolution had now become mathematics and hence an "exact" science.
In fact, ever since the thirties there were very few who dared to challenge the new-born science, for instance d'Arcy Thompson, Willis, Schindewolf, Goldschmidt and Severtsov. and they were treated more or less with scorn.
The intention of this section, besides outlining the history of the concept of natural selection, was to show that during the greater part of the history of Darwinism, the mechanism suggested by Darwin was not accepted. Moreover, if it is accepted today that is not because the mechanism as such has been demonstrated. To be sure the inheritance of changes brought about by mutations has been shown to occur in many cases, but successive accumulation has hardly been demonstrated, and even then there is no evidence that it could result in large modifications.