This volume differs from most other introductory texts in sociology. It is not an institutional survey of contemporary American society, nor is it an attempt to summarize in encyclopedia fashion all the various specialties that have developed in our discipline. Instead, it is a comparative and historical analysis of human societies, the largest, most powerful and most important social systems humans have created. The basic structure of the analysis is simple enough to be grasped by any student, yet the multilayered nature of the theory that guides the analysis can challenge the best of students. This volume is the fifth edition of Human Societies. As authors, we have been extremely pleased with the reception accorded previous editions by both students and instructors. We have been especially pleased with the opportunity that each new edition has provided for refinements in both the underlying theory and its presentation. We hope that this new edition lives up to the standards of its predecessors.