Where do social structures come from?

While structuralism and network theory have been enormously successful empirically, they have not been able to explain the origins of social structures and networks. I contend that the emerging field of evolutionary psychology can help us explain how some social structures and networks emerge. I illustrate my point with a persistent empirical puzzle in the social networks literature (why women have more kin in their personal networks than men do), and provide an evolutionary psychological explanation for this phenomenon. I test two implications of this explanation with the 1985 Social Networks module of the General Social Survey. The data provide support for the evolutionary psychological explanation of women's kincentric networks.