"Impacts of Climatic Variability and Population Growth on the Virgin Branch Anasazi Cultural Developments" (with Joel Michaelsen). American Antiquity 55(2): 227-250, 1990.

Abstract Two major drought episodes, AD 1000 to 1015 and AD 1120 to 1150, contributed to significant change in adaptive strategies of the Virgin Branch Anasazi, a prehistoric population that occupied the southwestern Great Basin between AD 100 and AD 1150. The first extreme climatic event promoted the adoption of several alternative-buffering strategies including intensive agricultural practices, increased reliance on storage, and the organization of large residential labor groups. The second drought, which followed 150 years of favorable climatic conditions and high levels of population growth, had a devastating impact upon the Virgin Branch Anasazi resulting the complete abandonment of the southwestern Great Basin by that group. These two climatic events required entirely different responses, which suggest that shifts in climate are best viewed as triggering culture change. The preconditions of population growth set the various levels of sensitivity to extreme climatic events and determine the precise nature of the culture changes.

The purpose of this paper is to examine the roles of population growth and climatic variability in producing culture change among the Virgin Branch Anasazi, a prehistoric population that occupied the southwestern Great Basin between AD 100 and AD 1150. Reconsturctions of both population and climate were developed using data from independent sources of evidence. Patterns of population growth and cultural change were determined from careful archaeological surveys and climatic history for the region was reconstructed using tree rings, which permitted the independent examination of each factor.