Boas’s rejection of the traditional view was truly radical; it simply denied the existence of any significant innate differences between savage, colored people and civilized, white people. The differences in physical appearance, in short, did not lead to any significant difference in mental or social function. That there were observable social differences was undeniable, but the explanation for those differences. Boas maintained, was that they were the product of different histories, not different biological experiences.
In Search of Human Nature
Carl Degler's book tracing the decline and revival of Darwinism in American social thought.