The man who showed that differences between human groups are often the result of their distinctive cultural environments, rather than inherited biological traits.
"(His) ideas challenged prevailing conceptions of racial and social hierarchy. Where the natural sciences had taught that humans were divided into fixed, biological types, Boas argued that the data called for a more nuanced account of human difference. Contrary to the dispensations of social Darwinism, he contended, differences observed across human groups—from the physical to the cognitive and social—were often the result of their distinctive cultural environments, rather than inherited biological traits. His many influential students would extend this insight to other categories used to sort people. For them, all observable differences—in sexual mores, in religious beliefs, in everyday customs—reflected the variety of ways humans had devised for living, no one way superior to any other. 'Cultural relativism,' as it became known, was born."
Book Review: Gods of the Upper Air: How a Circle of Renegade Anthropologists Reinvented Race, Sex, and Gender in the Twentieth Century