Charles Darwin book The Descent of Man, and Selection in Relation to Sex
volume I, chapter V: "On the Development of the Intellectual and Moral Faculties during Primeval and Civilised Times" (second edition, 1874) pages 133-134 http://darwin-online.org.uk/content/frameset?pageseq=156&itemID=F944&viewtype=image <br class="br">The last sentence of the first paragraph is often quoted in isolation to make Darwin seem heartless. <br class="br">The Descent of Man (1871)