The process by which populations of organisms change over successive generations through the differential survival and reproduction of heritable traits — the foundational explanatory framework of modern biology, and one of the most contested scientific ideas in the history of human culture.
Evolution is the only scientific theory that has been simultaneously accepted as fact by essentially the entire scientific community and rejected by a majority of citizens in one of the world's most scientifically advanced nations. This gap between scientific consensus and public acceptance is not a failure of communication. It is the product of a collision between an explanatory framework and beliefs about human origin, moral status, and divine order that evolution touches more directly than any other scientific idea. Understanding evolution requires understanding both what it explains and why it has been used as a weapon in conflicts it did not create.