Abstract
In this chapter, we discuss the logic driving the evolution of inbreeding avoidance systems. In addition, we review literature regarding the negative effects of inbreeding, discuss how disparate opportunity costs shaped sex differences regarding the avoidance of inbreeding, and briefly discuss recent research on the information‐processing architecture of systems that evolved to identify and sexually avoid close genetic relatives. Last, we discuss the possible origins of the incest taboo. In particular, we question whether attitudes regarding third‐party inbreeding are evolved adaptations to regulate the behavior of others or merely by‐products of systems designed to guide personal mating decisions.