By the early 20th century, a massive shift occurred, led by , the "Father of American Anthropology." Boas rejected universal laws in favor of Historical Particularism , arguing that every culture is a product of its own unique history. He introduced the concept of cultural relativism—the idea that a culture should be understood on its own terms rather than judged against a European standard.

In the mid-20th century, introduced Structuralism , looking for the deep, underlying patterns of the human mind. He argued that beneath the surface of different myths and kinship systems lies a universal mental structure based on "binary oppositions" (like nature vs. culture).

The Evolution of Anthropological Thought: History and Theory