Darwin's findings might have settled as securely into scientific orthodoxy as such previous discoveries as the circulation of the blood or the workings of the solar system did, but for the challenge they posed – and, for some, still pose – to the Old Testament account of the Creation. There could be no such thing as evolution, they protested, because a divine being had created all life fully formed.

The question of human descent from primordial apes is barely touched on in The Origin Of Species, and was only elaborated in a later work of Darwin's, but it follows logically from the theories set out there. As well as his work on natural selection, Darwin wrote a late work about emotional expression, which anticipated anthropological findings in that area by the best part of a century.