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 those defending immutability of species, and in effect said that the book offered the best explanation "ever published of the manner of formation of species", though he did not agree with it in all respects. He still had the gravest doubts that transmutation would bestialise man. It appears that Darwin had assured Owen that he was looking at everything as resulting from designed laws, which Owen interpreted as showing a shared belief in "Creative Power". Darwin had already made his views clearer to others, telling Lyell that if each step in evolution was providentially planned, the whole procedure would be