This book examines sociobiology's validity and significance, using the sociobiological theory of the evolution of mating and parenting as an example. It identifies and discusses the array of factors that determine sociobiology's effort to become a science, providing a rare, balanced account--more critical than that of its advocates and more constructive than that of its critics. It sees a role for sociobiology in changing the way we understand the goals of evolutionary biology, the proper way to evaluate emerging sciences, and the deep structure of scientific theories. The book's premise is that evolutionary biology would not be complete if it did not explain evolutionarily significant social facts about nonhumans and humans. It proposes that explanations should be evaluated in terms of their basis in underlying theories, research programs, and conceptual frameworks.