Book excerpt: This book represents a major theoretical synthesis between the life sciences and the social sciences. Peter Corning shows that the selective advantages arising from various kinds of cooperation - from single-celled creatures to wolf packs to modern nation-states - are the cause of the directional aspect of evolutionary history, that is, the progressive emergence of more complex, hierarchically organized systems in the biological , cultural, and political realms. The Synergism Hypothesis spans a vast intellectual and scientific territory and speaks to the central concerns of evolutionary biology, sociobiology, anthropology, psychology, economics, sociology, and political science. It is an extraordinary contribution, which should influence all future discussions of why we behave the way we do. -- from back cover.