El origen del hombre
In 1871, Darwin published "The Descent of Man, and Selection in Relation to Sex", which contained his views on human evolution. Darwin argued that the differences between the human mind and the minds of the higher animals were a matter of degree rather than of kind. For example, he viewed morality as a natural outgrowth of instincts that were beneficial to animals living in social groups. He argued that all the differences between humans and apes were explained by a combination of the selective pressures that came from our ancestors moving from the trees to the plains, and sexual selection. The debate over human origins, and over the degree of human uniqueness continued well into the 20th century.