On the Origin of Species for Existence" Darwin includes "slow-breeding man" among other examples of Malthusian population growth. In his discussions on morphology, Darwin compares and comments on bone structures that are homologous between humans and other mammals. Darwin's early notebooks discussed how non-adaptive characteristics could be selected when animals or humans chose mates, with races of humans differing over ideas of beauty. In his 1856 notes responding to Robert Knox's "The Races of Man: A Fragment", he called this effect sexual selection. He added notes on sexual selection to his "big book on species", and in mid-1857 he added a section heading; "Theory applied
Reactions to On the Origin of Species of Selection". Darwin now worked on an "abstract" trimmed from his "Natural Selection" manuscript. The publisher John Murray agreed the title as "On the Origin of Species through Natural Selection" and the book went on sale to the trade on 22 November 1859. The stock of 1,250 copies was oversubscribed, and Darwin, still at Ilkley spa town, began corrections for a second edition. The novelist Charles Kingsley, a Christian socialist country rector, sent him a letter of praise: "It awes me...if you be right I must give up much that I have believed", it was "just as noble a conception