Fleming Jenkin review

Fleming Jenkin reviews a later edition of the Origin of Species

... Suppose a white man to have been wrecked on an island inhabited by negroes.... Our shipwrecked hero would probably become king; he would kill a great many blacks in the struggle for existence; he would have a great many wives and children, while many of his subjects would live and die as bachelors.... Our white's qualities would certainly tend very much to preserve him to good old age, and yet he would not suffice in any number of generations to turn his subjects' descendants white.... In the first generation there will be some dozens of intelligent young mulattoes, much superior in average intelligence to the negroes. We might expect the throne for some generations to be occupied by a more or less yellow king; but can any one believe that the whole island will gradually acquire a white, or even a yellow population ...?

Here is a case in which a variety was introduced, with far greater advantages than any sport every heard of, advantages tending to its preservation, and yet powerless to perpetuate the new variety.

- North British Review, June 1867, 46:277-318.

On the theory of blending inheritance tacitly assumed by Darwin and most other 19th century biologists, offspring would combine the traits of their parents and thus tend to fall halfway in between them. Disregarding the casual racism of the example, Jenkins' point is perfectly valid: Darwin said that this objection gave him more trouble than any other. Darwin subsequently developed a theory of Pangenesis, in which parts of the body emitted gemmules that accumulated in the gonads: modification of characters by natural selection would then modify the gemmules, which would be transmitted to the next generation. This essentially Lamarckian idea was Darwin's biggest scientific error. Even as Darwin propounded his theory, Gregor Mendel had already shown that heredity is particulate rather than blending. Elaboration of the Genetical Theory of Natural Selection by R. A. Fisher in 1925 laid the foundations for modern genetic selection theory.