The principal feature of Charles Darwin's theory of evolution. Rejecting the idea of a special creation or of supernatural influences, Darwin (1809-82) held that the variety of species among living things is explainable naturally. There is a process at work in the world whereby individual variations beneficial to an organism in a given environment naturally tend to become perpetuated in later generations. The strong (and fittest) not only survive by adapting to circumstances, but they mysteriously change species in the process of survival. Darwin's basis for natural selection has yet to be proved scientifically.