El origen del hombre
Even at this late stage Darwin was uncertain as to whether to include a chapter on mankind. At the end of January he wrote to Murray: "I feel a full conviction that my Chapter on man will excite attention &amp; plenty of abuse &amp; I suppose abuse is as good as praise for selling a Book" but he then apparently decided against the idea for a week later in a letter to his close friend Joseph Hooker he explained "I began a chapter on Man, for which I have long collected materials, but it has grown too long, &amp; I think I shall publish separately a very small volume, 'an essay on the origin of mankind'". This "essay" would become two books: "The Descent of Man, and Selection in Relation to Sex" (1871) and "The Expression of Emotions in Man and Animals" (1872).