Franz Boas' major contribution to anthropology was his denial of race as a biological construct. During the late 19th century, anthropologists used biological features to justify racial divisions. Boas disagreed with this and proved that physical features are a result of evolution in one's environment, not evidence of human species.
This idea opened up the possibility of social change, allowing for the idea that every race was equally capable of cultural development.
Boas later created the ideology of cultural relativism based on racial equality. Cultural relativism states that no culture can be labeled as better or worse, constructs that were based on the culture's similarity to European norms. Instead, Boas believed that anthropologists should understand each culture through its own lens and judge it according to its own social standards.