An assessment of settlement and subsistence in emergent agricultural economies in the Tucson Basin, United States, and Chihuahua, Mexico

Recent archaeological investigations in the Chihuahuan and Sonoran deserts challenge notions about Early Agricultural period (EAP; 1500 BC to AD 200) settlement-subsistence systems in the American Southwest and northwestern Mexico. Previously, archaeologists believed that 4000 years ago cultigens were carried from Mexico into the uplands of Arizona and New Mexico where they remained largely insignificant until around AD 1. Excavations at EAP sites in Arizona and Chihuahua refute these notions by demonstrating that residentially stable locales were established in the desert borderlands 3000 years ago, and that maize cultivation and production increased relative to the hunting and gathering of wild resources. Settlement changes are evidenced by the appearance of extensive pithouse sites in the Sonoran desert and terraced hilltop complexes in the Chihuahuan desert.;While the settlement and subsistence changes are well documented, some issues still remain unclear including the ways in which inhabitants of the Chihuahuan and Sonorant deserts responded to the adjustments associated with increasing food production, and whether these sites represent short-term occupations or residential settlements. My dissertation clarifies these questions by examining subsistence remains from eight San Pedro phase (1500 to 800 BC) sites in the Rio Casas Grandes Valley and the Tucson Basin. This study documents the variability between the San Pedro phase settlement and subsistence systems of these two areas and examines the following questions: (1) how did the adoption of agriculture impact the success of extractive economies, (2) are there differences in the relative ubiquity of cultigens, and (3) are there differences in the size, duration, and seasonality of settlements?;This research provides valuable information on incipient agricultural practices in the desert borderlands, a topic not often addressed simultaneously on both sides of the international border. More importantly, by using a comparative approach to examine coeval changes in the Sonoran and Chihuahuan Deserts, this study provides a more sophisticated understanding of variable cultural responses to qualitatively different and environments. The occupation of the cerros de trincheras in the Rio Casas Grandes Valley was a short-lived phenomenon perhaps owing to the unpredictable, unstable, and biotically less productive nature of the Chihuahuan desert. To the contrary, the early farming adaptation in the Tucson Basin was successful for many subsequent centuries into the historic and modern periods, suggesting that the very nature of the Sonoran Desert provided cultural and ecological advantages that the Chihuahuan Desert could not provide to its Early Agricultural period inhabitants.