Effort to answer ancient mystery garners international acclaim

Whatever caused the sudden depopulation of the American Southwest’s Mesa Verde region in the late AD 1200s is one of the greatest mysteries in archaeology today.

Why did tens of thousands of Pueblo farmers leave their ancient homeland in southwestern Colorado and migrate south and southeast, where their descendants live today?

This famous exodus is among puzzles investigated by the Village Ecodynamics Project (VEP), a multidisciplinary, multi-institution research effort led at WSU by Tim Kohler, Regents Professor of anthropology. VEP recently gained international acclaim as one of 10 projects honored at the Shanghai Archaeology Forum (SAF) for producing “major archaeological research findings.”

Archaeology experts from around the world chose VEP, from among 99 nominated projects, for having “achieved distinction in innovative, creative, and rigorous works, and generated new knowledge about our human past.” This fall, Kohler traveled to China with longtime colleague Bill Lipe, emeritus professor of anthropology, to accept the award and present VEP research on SAF’s global stage.

“This project illuminates a new way forward in which archaeologists can ask, and hope to answer, questions they have never been able to consider,” Lipe said.

The key is a unique “combination of modeling and empirical research that is much more powerful than either approach would be by itself. It exemplifies a rigorous and systematic new approach to archaeology that is our most promising future,” Lipe said.

Modeling across millennia

Launched in 2001, VEP uses novel computer simulation techniques to examine the ways the Pueblo societies responded to environmental changes, “and also how they changed their environments,” Kohler said. Climate change and intercommunity warfare are prime suspects in the sudden desertion of the large Mesa Verde region, which extended from what is now Mesa Verde National Park in Colorado west into southeastern Utah.

“Then, as now, climate change caused stress to the coupled social and environmental systems,” Kohler said. While most studies point to severe shortages of critical resources amid increasingly dense populations in an area marginal for farming, other studies suggest significant sociopolitical changes occurred just before the mass migration.

Armed with this knowledge, sociologists and anthropologists can better predict how contemporary societies will respond to climate change.

Through their “agent-based” models, VEP researchers simulate where prehistoric people of the American Southwest would have situated their households based on both the natural and social environments in which they lived.

The researchers input various important factors—such as farming soil, access to water, and access to animals for hunting—in attempt to recreate the human and climatic conditions of the time. Simulated residents (“agents”) situate themselves on the landscape in relation to these critical resources, while taking into consideration the locations of other households with whom they interact. The resulting settlement patterns are compared to the actual archaeological record, enabling researchers to draw more informed conclusions about what may have occurred in the prehistoric past.

The model systems show high levels of response to the effects of climatic changes on the landscape and to resource depletion by the large population of farmers. By evaluating the possibility of crises in potable water, woody fuels, and protein, the research is helping to determine whether critical resource shortages or social factors most influenced the depopulation.

“VEP has made progress in understanding why dramatic demographic and socio-cultural changes occurred in prehistoric Pueblo societies, and even more progress in documenting precisely how and when these changes took place,” Lipe said.

Since the mid-1990s, social science researchers have grown more interested in computational approaches, including simulation. This increase appears to be driven by both a cross-disciplinary interest in the sciences of complexity and ever-increasing computational capacity.

In the past, the complexity of the phenomena forced researchers to use simplistic world models. Today, they are able to study a world in which most important phenomena emerge from the non-linear interaction of many agents (physical, biological, social) in systems that are rarely at equilibrium.