By combining an original thesis and a representative body of ethnographic data, this ambitious work seeks to describe and explain the growth in complexity of human societies. Its emphasis is on the causes, mechanisms, and patterns of cultural evolution, which the authors explain in terms of a coherent theory of political economy defined as the mobilization and exchange of goods and services between families. The authors show that the interconnected processes of technological change and population growth are the motor of social change, resulting in three related processes intensification, integration, and stratification that transform human societies over time. The validity of their theory rests on evidence drawn from 19 case studies that range widely over time and space.