A 19th-century theory proposed by British sociologist Sir Francis Galton and loosely based on Darwinism, by which the social order is said to be a product of natural selection of those individuals who are best suited to existing living conditions. A “struggle for existence” and “survival of the fittest,” terms coined by U.S. sociologist William Sumner, were seen as the ultimate motives for human action and social organization. Although concepts of biological determinism predated Charles Darwin’s Origin of Species (1859), such notions became popular in the late 19th and early 20th century, particularly when applied to the rivalries of great powers or to justify or condemn social and political theories. Social Darwinists in both Europe and the United States applied the principles of evolution as a means of explaining the origin and propriety of human characteristics and institutions, though opinions varied widely over just how Darwin’s theories ought to be applied.
This highly interpretive approach to the science of evolution was essentially political; the particular version of Social Darwinism favored by various professional and academic circles tended to accord with the interests and agendas of those circles. In the United States and England, Social Darwinism was seen to reinforce capitalism and laissez-faire as natural and inevitable. German Social Darwinists, on the other hand, advocated state intervention to halt the supposed “degeneration” of the human species. Social Darwinist theories were advanced to describe and address in biological terms a broad range of human conditions including delinquency and criminality, intelligence, mental illness, poverty, susceptibility to dis¬ ease, and other traits thought to separate the “fit” from the “unfit.”