Cliff palace in Mesa Verde, CO, 1891 (Photo: Gustaf Nordenskiöld/Public Domain)

Adapted from Washington State University News


Climate problems alone were not enough to end periods of ancient Pueblo development in the southwestern United States. 

Drought is often blamed for the periodic disruptions of these Pueblo societies, but in a study with potential implications for the modern world, scientists have found evidence that slowly accumulating social tension likely played a substantial role in three dramatic upheavals in Pueblo development.

The findings detailed in an article in the Proceedings of the National Academy of Sciences, show that Pueblo farmers often persevered through droughts, but when social tensions were increasing, even modest droughts could spell the end of an era of development. 

Co-authored by SFI External Professor Tim Kohler at Washington State University and External Professor Marten Scheffer at Wageningen University in The Netherlands, the study is one of several to result from a working group on climate change and “The Human Niche” that convened at SFI in July of 2018.

Using tree-ring analyses of wood beams used for construction, which provided a time series of estimated tree-cutting activity spanning many centuries, the researchers found that weakened recovery from interruptions in construction activity preceded three major transformations of Pueblo societies. These slow-downs were different than other interruptions, which showed quick returns to normal in the following years. The archeologists also noted increased signs of violence at the same time, confirming that tension had likely increased and that societies were nearing a tipping point.

“This record is like a social thermometer,” said Kohler. “Tree cutting and construction are vital components of these societies. Any deviation from normal tells you something is going on.” 

“Those warning signals turn out to be strikingly universal,” said Scheffer, first author on the study. “They are based on the fact that slowing down of recovery from small perturbations signals loss of resilience.” 

Read the paper, "Loss of Resilience Preceded Transformation of Prehispanic Pueblo Societies," in PNAS (April 28, 2021)

Read the full press release at Washington State University News (April 27, 2021)