This article analyzes several more or less public controversies around evolutionary psychology and sociobiology. It is asked how participants in the debate draw the lines between science and non-science and what is at stake in their boundary work practices. Evolutionists and their critics practice boundary work both in scientific insider debates and in public scientific controversies. All contenders agree that science is characterized by authority relations and disciplinary gatekeepers and that science is distinguished from other social practices and by a certain code of conduct. Evolutionists and their critics differ in their assessment of scientific authorities’ roles and responsibilities, in their definition of scientific code of conduct, and in their conception of the relation between science and society. The analysis offers insights into the social production of knowledge in both scientific and public discourse and into the ways in which scientists negotiate the very nature of science as such.