Sexual behavior and social behavior are profoundly alike in that both involve one set of individuals more or less willingly providing a limiting resource to another set (Queller 1994). Thus, in sexual interactions females provide resource–rich ova and other parental investment to males, and in social interactions workers provide labor to queens. In both situations, the parties are virtually always in conflict over the allocation of the resources, but their interests also partly coincide: eggs must be fertilized and offspring produced, and a new generation of reproductives must be successfully protected and reared. The complex mixtures of conflict and cooperation that thus typify sex and sociality make them among the most endlessly fascinating and difficult topics in ecology and evolution.

This book, and its companion (Choe and Crespi 1997), explore the intricacies of sexual and social competition. We have drawn together, for each of these topics, a set of authors whose expertise is both taxon–deep and broadly based in the theory that guides interpretation of natural history. Our goal has been to bring theory and observation together, to find parallels and convergences between disparate taxa, and to sketch out the patterns of engagement that will allow us to understand how conflicts and confluences of interest evolve together.