Modeling Environmental and Demographic Effects on Population Size in the Southwest United States

Population settlement, growth, expansion, and eventual abandonment of ancestral Pueblo sites in the Four Corners region of the United States have posed enduring questions for archaeologists and paleodemographers about the nature of patterns of population growth and cultural change in the region. In order to answer these questions, it is essential to have good estimates of demographic parameters as well as an understanding of how these parameters have led to changes in population size and distribution. Neither the appropriate data nor this understanding are easily derived from the archaeological record, however. Agent-based computer simulations are increasingly being used to overcome these and other deficiencies in available archaeological data. The Artificial Anasazi model was developed in the late 1990s for this purpose. The model simulates the rise and fall of populations in the Long House Valley, located in northeastern Arizona. Extensive archaeological and environmental data provide a framework to ensure that model parameters are grounded in reality. The Artificial Anasazi model and its successor, the Artificial Long House Valley model, focus on demographic changes at the household and individual levels, particularly in relation to variability in underlying environmental influences. This talk will describe the basic structure of these models and highlight results that inform about the influence of both the environment and demographic processes on the population history of the Long House Valley. Special consideration is given to processes that operate at different levels, including the impact of aggregate vs. individual structures and constant vs. age-specific fertility and mortality processes. Ultimately these models will be used in efforts to measure the effects of infectious disease, changes in fertility and mortality, changes in the environment, and other factors on the population dynamics of the valley beginning in AD 800 until its abandonment around AD 1300.