Hydroclimate Variability and the Evolution of Socioecological Complexity in Dryland Farming Communities

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Understanding the ecological constraints on the evolution of social complexity in dryland ecosystems remains a major challenge in archaeological research. Most global case studies of foraging-farming transitions in drylands lack the requisite chronological precision and fine-grained environmental information necessary to reconstruct the subtle interactions between environment and society during these important moments of subsistence change, population growth, and social development. Early societies in western North America provide a rare example of the ephemeral adoption of agriculture and development of social complexity. Imprecise chronologies for relevant horticultural villages and their immediate hydroclimatic contexts have led to a lack of consensus on the development of social complexity. This project tests two hypotheses about the formation of such villages: the largest and most socially complex villages had the longest occupation spans; and the longest occupied villages occurred in river basins that are least sensitive to hydroclimate variability regimes. The project provides research sites for participants in the Utah State University Native American Summer Mentorship Program, a focused research experience for native students that encourages transfer and successful degree completion. The PIs collaborate with faculty and students at the Eastern Prehistoric Museum and Anthropology Museum to develop a traveling exhibit of the project findings that will be hosted at four public museums throughout the state for three months each. A three-part lecture series accompanies the exhibit where each project investigator presents the results of their individual studies. The research team will develop tree-ring-based reconstructions of local stream discharge for the last two millenia, build and test a basin sensitivity model connecting local hydroclimate and geomorphic variables, and evaluate village longevity, size and complexity using high-density, high-precision chronological models. Communities that developed under conditions where vulnerability thresholds were crossed with less frequency should have longer occupational durations, larger sizes, and more evidence of complexity. This project provides a comparative framework explaining the fundamental processes of agricultural community formation and stability that enabled the growth of populations and social complexity in dryland ecosystems. The project systematically combines dendrochronology, geoarchaeology, and high-precision archaeological radiocarbon dating to resolve time at the multidecadal/multigenerational scales necessary to capture the dynamic social-ecological processes constraining the stability, size, and development of social complexity in early agricultural societies. The project findings are a key case study in the global comparative analyses of the sustainability of past and modern dryland agricultural societies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.