- Charles Darwin, Descent of Man, and Selection in relation to Sex, 2 vols. (1871), vol. 1, F937.1.; and vol. 2, F937.2.
In 1871 Charles Darwin published a two-volume work which followed up on the brief aside in the Origin that his theory might throw light upon the origin of humans. In the Descent of Man he explored embryological resemblances between humans and other animals.
Darwin also offered sexual selection as an additional form of natural selection to account for pronounced differences between the male and female (sexual dimorphism).
Darwin admitted that the beautiful feather of the peacock gave him a headache. But with sexual selection, one might account for fancy tail feathers, after all, that seemed to be more for show than for function.