This chapter examines socialization and the process by which social norms become internalized, how this capacity for internalization could have evolved, and why the norms internalized tend to be group-beneficial. It begins with a discussion of cultural transmission and how it overrides fitness by taking account of two facts. First, the phenotypic expression of an individual's genetic inheritance depends on a developmental process that is plastic and open-ended. Second, this developmental process is deliberately structured—by elders, teachers, political leaders, and religious figures—to foster certain kinds of development and to thwart others. The chapter then introduces a purely phenotypic model in which, as a result of the effectiveness of socialization, a fitness-reducing norm may be maintained in a population. It also describes the gene-culture coevolution of a fitness-reducing norm before concluding with an analysis of the link between internalization of norms and altruism.