This volume explores the spatial and temporal boundaries of whole systemic interpolity systems (world-systems) since the Stone Age. By delineating boundaries of integration based on political/military interaction and on long-distance trade, it compares entire systems of human interaction to examine their similarities and differences, while also addressing the causes of long-term increases in the scale and complexity of human polities and interaction networks. The growing awareness of Eurocentrism suggests the need to systematically compare the world-system that emerged in Europe with interstate systems that existed in other regions and in the more distant past to test hypotheses about the general causes of structural changes – especially the emergence and development of sociocultural and organizational complexity and hierarchy. This book develops a systematic method for determining when and where regional interaction systems merged with one another to become the global system that we have today. Defining interstate systems as networks of polities that make war and form alliances with one another, the contributing authors formulate explicit decision-making rules for specifying the spatial and temporal extent of these important geopolitical and trade interaction networks, starting with those regions in which large cities first appeared. An improved, scientific grasp of interstate systems has important implications for explaining the evolution of human economic, geopolitical, and cultural institutions in the past and for better comprehending the possibilities and probabilities of further geopolitical evolution in the twenty-first century.