Population growth, social interaction, and environmental variability are interrelated facets of the same complex system. Tracing the flow of food, water, information, and energy within these social-ecological systems is essential for understanding their long-term behavior. Leveraging an archaeological perspective of how past societies coevolved with their natural environments will be critical to anticipating the impact of impending climate change on farming communities in the developing world. However, there is currently a lack of formal, quantitative theory rooted in first principles of human behavior that can predict the empirical regularities of the archaeological record in semiarid regions. Through a series of models -- statistical, computational, and mathematical -- and empirical data from two long-term archaeological case studies in the pre-Hispanic American Southwest and Roman North Africa, I explore the feedbacks between population growth and social interaction in water-limited agrarian societies. First, I use a statistical model to analyze a database of 7.5 million artifacts collected from nearly 500 archaeological sites in the Southwest and found that sites located in different climatic zones were more likely to interact with one another than a sites occupying the same zone. Next, I develop a computational model of demography and food production in ancient agrarian societies and, using North Africa as a motivating example, show how the concrete actions and interactions of millions of individual people lead to emergent patterns of population growth and stability. Finally, I build a simple mathematical model of trade and migration among agricultural settlements to determine how the relative costs and benefits of social interaction drive population growth and shape long-term settlement patterns. Together, these studies form the foundation for a unified quantitative approach to regional social-ecological systems. By combining theory and methods from ecology, geography, and climate science, archaeologists can better leverage insights from diverse times and places to fill critical knowledge gaps in the study of food security and sustainability in the drylands of today.

My dissertation contributes to a body of knowledge useful for understanding the evolution of subsistence economies based on agriculture from those based on hunting and gathering, as well as the development of formal rules and norms of territorial ownership in hunter-gatherer societies. My research specifically combines simple formal and conceptual models with the empirical analysis of large ethnographic and environmental data sets to study feedback processes in coupled forager-resource systems. I use the formal and conceptual models of forager-resource systems as tools that aid in the development of two alternative arguments that may explain the adoption of food production and formal territorial ownership among hunter-gatherers. I call these arguments the Uncertainty Reduction Hypothesis and the Social Opportunity Hypothesis. Based on the logic of these arguments, I develop expectations for patterns of food production and formal territorial ownership documented in the ethnographic record of hunter-gatherer societies and evaluate these expectations with large ethnographic and environmental data sets. My analysis suggests that the Uncertainty Reduction Hypothesis is more consistent with the data than the Social Opportunity Hypothesis. Overall, my approach combines the intellectual frameworks of evolutionary ecology and resilience thinking. The result is a theory of subsistence change that integrates elements of three classic models of economic development with deep intellectual roots in human ecology: The Malthusian, Boserupian and Weberian models. A final take home message of my study is that evolutionary ecology and resilience thinking are complementary frameworks for archaeologists who study the transition from hunting and gathering to farming.

The Hohokam of central Arizona left behind evidence of a culture markedly different from and more complex than the small communities of O'odham farmers first encountered by Europeans in the sixteenth and seventeenth centuries A.D. Archaeologists have worked for well over a century to document Hohokam culture history, but much about Pre-Columbian life in the Sonoran Desert remains poorly understood. In particular, the organization of the Hohokam economy in the Phoenix Basin has been an elusive and complicated subject, despite having been the focus of much previous research. This dissertation provides an assessment of several working hypotheses regarding the organization and evolution of the pottery distribution sector of the Hohokam economy. This was accomplished using an agent-based modeling methodology known as pattern-oriented modeling. The objective of the research was to first identify a variety of economic models that may explain patterns of artifact distribution in the archaeological record. Those models were abstract representations of the real-world system theoretically drawn from different sources, including microeconomics, mathematics (network/graph theory), and economic anthropology. Next, the effort was turned toward implementing those hypotheses as agent-based models, and finally assessing whether or not any of the models were consistent with Hohokam ceramic datasets. The project's pattern-oriented modeling methodology led to the discard of several hypotheses, narrowing the range of plausible models of the organization of the Hohokam economy. The results suggest that for much of the Hohokam sequence a market-based system, perhaps structured around workshop procurement and shopkeeper merchandise, provided the means of distributing pottery from specialist producers to widely distributed consumers. Perhaps unsurprisingly, the results of this project are broadly consistent with earlier researchers' interpretations that the structure of the Hohokam economy evolved through time, growing more complex throughout the Preclassic, and undergoing a major reorganization resulting in a less complicated system at the transition to the Classic Period.