What is social Darwinism and how was it tied to imperialism?

Social darwinism was a social theory that was taken from Darwin's own theory of natural selection, it was basically survival of the fittest. those who are meant to rise above the others will and in times of economic downturn the fittest will survive. social darwinism was used to justify imperialism because Survival of the fittest and competition between species was believed to be a necessary part of the social structure. the idea of social darwinism was that by the law of nature the stronger people should take over weaker ones.