The Evolution of Social Behavior in the Prehistoric American Southwest

Long House Valley, located in the Black Mesa area of northeastern Arizona (USA), was inhabited by the Kayenta Anasazi from circa 1800 B.C. to circa A.D. 1300. These people were prehistoric precursors of the modern Pueblo cultures of the Colorado Plateau. A 100-percent archaeological survey of the valley, supplemented with limited excavations, has yielded a rich paleoenvironmental record, based on alluvial geomorphology, palynology, and dendroclimatology, permitting accurate quantitative reconstruction of annual fluctuations in potential agricultural production (kg maize/hectare). In particular, the archaeological record of Anasazi farming groups from A.D. 200-1300 provided information on a millennium of sociocultural stasis, variability, change, and adaptation. We report on a multiagent computational model of this society that closely reproduces the main features of its actual history, including population ebb and flow, changing spatial settlement patterns, and eventual rapid decline. The agents in the model are monoagriculturalists, who decide both where to situate their fields as well as the location of their settlements. Nutritional needs constrain fertility. Agent heterogeneity is demonstrated to be crucial to the high fidelity of the model.