Biological causes of human social behavior will be invisible to those who follow the Durkheimian injunction to seek the causes of social facts in preceding social facts. Sociologists ignore or deny these biological causes at peril of grievous error. Biological causes can be integrated with traditional sociological models, but this approach will require sociologists to incorporate into their thinking the knowledge of disciplines whose paradigms offer biological explanations of the behaviors important to sociologists. I take examples of such knowledge from evolutionary biology, behavior genetics, and behavioral endocrinology.