The Descent of Man
Charles Darwin wrote Descent of Man in 1871, a work that chronicled his theory of evolution.
A quote from the work reads:
"Civilized races of man will almost certainly exterminate the savage races throughout the world ... The break between man and his nearest allies will then be wider, for it will intervene between man in a more civilized state, as we may hope, even than the Caucasian, and some ape as low as a baboon, instead of as now between the negro or Australian and the gorilla."
In The Descent of Man, Darwin proposes that his theory of evolution proposed in On the Origin of Species applies to humans, and considers the implications of this for science and society. He advocates the improvement of the human genetic population by eugenics, particually the extermination of the 'inferior' races. Darwin did not propose active extermination: He predicted that this would occur given sufficient time with or without deliberate attempt, as a consequence of natural selection.
Today anthropologists discount any true distinguishing characteristics between different races of humans. It has been noted that many people were racist in Darwin's sociological background, and that was not necessarily a defining feature that was unique to Darwin himself.