Darwin's greatest contribution to science is that he completed the Copernican Revolution by drawing out for biology the notion of nature as a system of matter in motion governed by natural laws. With Darwin's discovery of natural selection, the origin and adaptations of organisms were brought into the realm of science.
Herbert Spencer is famous for his doctrine of social Darwinism, which asserted that the principles of evolution, including natural selection, apply to human societies, social classes, and individuals as well as to biological species developing over geologic time
