This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book looks at how Boas's first Ph.D., Kroeber, argued that failure of anthropologists to accept germ-line inheritance in biology inevitably meant misreading cultures in the way nineteenth century anthropologists did: as evolving from savage to civilized in a crypto-biological and stadial way, thereby allowing supposed racial psychologies to contaminate both the biological and the social sciences. It demonstrates how well justified was Kroeber's reiterated protestation against this imputation. The book shows that biologists who signed on to the "same" Modern Synthesis were divided on the meaning of so basic a concept as "population thinking" and spite of their show of unanimity harbored different attitudes toward human equality. It looks at our focal figures and their opponents, scientists though they are, succeeding and failing to find persuasive lines of arguments, inventing and projecting authoritative personae, and eliciting commitment-inducing emotional responses from their audiences.