A. R. Wallace

Darwinism: Bibliographical Excerpts

[though not an argument for sexual selection, Wallace was adamantly against it, this passage suggests another reason sexual selection has its uses] "This constant preference of animals for their like, even in the case of slightly different varieties of the same species, is evidently a fact of great importance in considering the origin of species by natural selection, since it show us that, so soon as a slight difference of form or colour has been effected, isolation will at once arise by the selective association of the animals themselves; and thus the great stumbling-block of "the swamping effects of intercrossing," which has been so prominently brought forward by many naturalists, will be completely obviated." (Wallace AR (1890) Darwinism. MacMillan: London p. 173)

human evolution

Autism