Charles Darwin wrote The Descent of Man and Selection in Relation to Sex in 1871, a work that chronicled his theory of evolution. This work discusses the lineage of man, rather than the empirical decline of man and a fall from grace.
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."
Darwin believed and taught that Caucasians were "higher on the evolutionary scale" than Asians and Africans.
In The Descent of Man and Selection in Relation to Sex, 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, particularly 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. Darwin discussed the notion of an active Eugenics program, but considered it to be counter to the "noble" part of our nature.
Darwin published his ideas on human evolution in this two-volume book, which applies Darwinian evolutionary theory to human evolution, and details his theory of sexual selection, a form of biological adaptation distinct from, yet interconnected somehow with, natural selection. It discusses many related issues, including evolutionary psychology, evolutionary ethics, differences between human races (Darwin's clear white supremacist racist ideas were peppered there), the differences between sexes, the dominant role of women in mate choice, and the relevance of the evolutionary theory to society.
Today anthropologists reject 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.