El origen del hombre
Darwin's influential 1859 book "On the Origin of Species" did not discuss human origins. The extended wording on the title page, which adds "by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life", uses the general terminology of biological races as an alternative for "varieties" and does not carry the modern connotation of human races. In "The Descent of Man, and Selection in Relation to Sex" (1871), Darwin examined the question of "Arguments in favour of, and opposed to, ranking the so-called races of man as distinct species" and reported no racial distinctions that would indicate that human races are discrete species.