Social Darwinism is the theory that persons, groups, and races are subject to the same laws of natural selection as Charles Darwin had perceived in plants and animals in nature. According to the theory, which was popular in the late nineteenth and early twentieth centuries, the weak were diminished and their cultures delimited, while the strong grew in power and in cultural influence over the weak. Social Darwinists held that the life of humans in society was a struggle for existence ruled by "survival of the fittest," a phrase proposed by the British philosopher and scientist Herbert Spencer.

The theory of evolution by natural selection was proposed by Charles Darwin and Alfred Russel Wallace in 1858. They argued that species with useful adaptations to the environment are more likely to survive and produce progeny than are those with less useful adaptations, thereby increasing the frequency with which...