At the beginning of this book, we described group dominance societies as characterized by three distinct but interlocking forms of social group dominance: one based on an arbitrary-set distinction, one based on gender, and one based on age or, more specifically, the adult-child distinction. Understanding how the gender system relates to each of the other two dominance systems will reveal some important details about how group dominance societies work: why they contain each of the three forms of group dominance that they do, and how each form sustains and is sustained by the others. In this chapter we examine gender within dominance societies. In doing this, we explore gender differences in psychological orientations toward group dominance, political behavior, social roles that enhance or attenuate arbitrary-set hierarchy, sexual relationships, and parent-child relationships. In this exploration, we will provide theoretical and empirical evidence to substantiate our claim that gender is not simply another arbitrary-set distinction, but has unique properties not associated with that distinction. Although we do not reduce the psychology of gender to the psychology of arbitrary sets, we will argue that the psychology of gender is a crucial component of the psychology of intergroup politics. Finally, we will also provide a theoretical explanation for the subordinate male target phenomenon documented in many studies of institutional discrimination. To accomplish these goals, we will employ the conceptual framework of contemporary evolutionary psychology.