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
On the Origin of Species and claimed it included false metaphysics. Darwin made extensive revisions to the sixth edition of the "Origin" (this was the first edition in which he used the word "evolution" which had commonly been associated with embryological development, though all editions concluded with the word "evolved"), and added a new chapter VII, "Miscellaneous objections", to address Mivart's arguments. The sixth edition was published by Murray on 19 February 1872 as "The Origin of Species", with "On" dropped from the title. Darwin had told Murray of working men in Lancashire clubbing together to buy the 5th edition at fifteen shillings and wanted