The Descent of Man

Charles Darwin's 1871 sequel to On the Origin of Species — extending evolutionary theory to humans, with extensive treatment of sexual selection

Tradition: Nineteenth-century evolutionary biology

Humans as the product of evolutionary descent — and the theory of sexual selection as a major mechanism of evolutionary change

Published by John Murray in two volumes in February 1871, 'The Descent of Man, and Selection in Relation to Sex' is Darwin's belated application of evolutionary theory to humans (deliberately omitted from the Origin of Species in 1859 as too inflammatory for that book's reception). Part I (vol. 1, plus the first three chapters of vol. 2) argues for human descent from non-human ancestors via natural selection, drawing on comparative anatomy, embryology, the geographical distribution of races, and the mental and moral faculties shared with other animals. Darwin treats reason, language, religious feeling, moral sense, and aesthetic appreciation as all having continuous evolutionary precedents in animals — a position he supports with extensive observational data on primates, dogs, birds, and insects. Part II (the bulk of vol. 2) develops the theory of sexual selection: selection for traits attractive to mates (peacock's tail, deer antlers, the elaborate plumage of male birds, human aesthetic preferences) rather than those merely useful for survival. Sexual selection explains, Darwin argues, the differences between human races (he sees these as superficial-aesthetic rather than capacity-significant) and between men and women (he takes Victorian sex-roles broadly for granted, a position later feminist-Darwinians would reconstruct). The book's reception was controversial but rapidly absorbed into nineteenth-century thought; Darwin's grandfather Erasmus Darwin and his contemporary Wallace had both anticipated parts of the human-evolution thesis, but Descent of Man supplied the empirical-comprehensive case.