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 was out.— The Bookseller said he had not read it but had heard it was a very remarkable book!!!" In December 1859 the botanist Asa Gray negotiated with a Boston publisher for publication of an authorised American version, however, he learnt that two New York publishing firms were already planning to exploit the absence of international copyright to print "Origin". Darwin wrote in January, "I never dreamed of my Book being so successful with general readers: I believe I should have laughed at the idea of sending the sheets to America." and asked Gray to keep any profits. Gray managed