This paper addresses two topics central to the study of nonhierarchical, regional social networks sometimes termed "tribal" social networks: 1) alternative models of the evolution of regional integration: and 2) the archaeological determination of characteristics of such regional networks. Problems in previous ethnological and archaeological studies are identified, and an alternative model is proposed. this is based on a more general theory of organizational processes in nonhierarchical social systems. Data from the prehistoric North American Southwest and Midwest are shown to support the more general model, which treats such networks as organizational responses to increasing environmental uncertainty occasioned by either cultural or physical ecological factors, or both.