In the movie Expelled, Ben Stein visits Nazi execution camps where those deemed to be mentally weak or disabled were murdered. The film examines how Nazis used some of the main tenets in Darwinian evolution to justify those atrocities—in particular they were influenced by the ideas of survival of the fittest and natural selection.
Charles Darwin wrote about these ideas in The Descent of Man (1871): "With savages, the weak in body or mind are soon eliminated; and those that survive commonly exhibit a vigorous state of health. We civilised men, on the other hand, do our utmost to check the process of elimination; we build asylums for the imbecile, the maimed, and the sick; we institute poor-laws and our medical men exert their utmost skill to save the life of every one to the last moment. There is reason to believe that vaccination has preserved thousands, who from a weak constitution would formerly have succumbed to small-pox. Thus the weak members of civilised societies propagate their kind. No one who has attended to the breeding of domestic animals will doubt that this must be highly injurious to the race of man. It is surprising how soon a want of care, or care wrongly directed, leads to the degeneration of a domestic race; but excepting in the case of man himself, hardly anyone is so ignorant as to allow his worst animals to breed."
