Time and again, drought was the final straw that disrupted complex ancestral Puebloan societies in the Southwest and shifted the cultures, according to a new study.
“Those societies took a long time to build and a very short time to collapse,” said Washington State University anthropologist R. Kyle Bocinsky, one of the study’s lead authors. “We think those collapses were tied to slightly worse-than-normal climate challenges that undermined leadership and social consensus.”
Pueblos and villages around Mesa Verde rose to prominence beginning in A.D. 1145. By 1285, they were completely abandoned, following several years of drought, in one of the great mysteries of the Southwest.
But a similar rise and fall among ancient pueblos had happened three times in the previous 900 years, Bocinsky and three other researchers said in their report, “Exploration and exploitation in the macrohistory of the pre-Hispanic Pueblo Southwest,” published April 1, in the journal Science Advances.
The Chaco civilization grew into a major trading and ceremonial center from A.D. 890 to the mid-1100s. By 1145, it was over.
A similar occurrence happened among pueblos from A.D. 700 to 890 and again during the Basketmaker III era, between A.D. 500 and 700. Each time, the Pueblo people dispersed, looked for new places to farm, came together and reinvented their societies.
Drought alone didn’t cause the societies to collapse, said Bocinsky, who is now director of sponsored projects at Crow Canyon Archaeological Center in Cortez.
But when their corn harvests were slim even though they had performed ceremonies correctly, people stopped believing in their leaders, and the social fabric cracked.
Timothy A. Kohler, another of the study’s authors, said the ancestral Puebloan societies were “woven together with a web of ceremony and ritual that required belief in the supernatural” to ensure plentiful rain and good crops.
When rains failed to appear, he said, the rituals lost legitimacy. “Then there’s a point where people say, ‘This isn’t working. We’re leaving,’ ” said Kohler, an archaeologist and external faculty member with the Santa Fe Institute.
Bocinsky, Kohler and two other scientists analyzed data from 1,002 distinct archaeological sites and nearly 30,000 tree-ring samples from across the Four Corners region using supercomputers. It was the first such attempt to use a massive amount of data points to construct a look at where people grew corn and how that influenced migrations across the landscapes.
The tree-ring data from ancient forests and from timber used in ancestral Puebloan structures helped the scientists figure out where and when ancestral people were growing maize and constructing buildings. The data also showed them exactly where and when drought was happening across the landscape.
Each major rise, collapse and shift of ancestral Puebloan societies followed a similar pattern, Bocinksy said. Ancestral Puebloan people looked for new places to grow maize, watered from streams and rain. Independent farmers and families joined into larger villages. They agreed on ways to store food, on ceremonies and on how to conduct themselves socially.
The more complex societies, like those at Chaco Canyon and Mesa Verde, were the least equal. Evidence at the ancient sites show some people lived in a version of McMansions, while others lived in small rooms. “We see differences in terms of burial, room sizes, diet,” Bocinksy said.
“We see this rising inequality that arrives at a crescendo. Then when the society falls, we see a shift to more equality,” he said.
Kohler agreed. “After the Pueblo I collapsed around (A.D. 900), people in a sense voted for hierarchy. They said, ‘Let’s go with Chaco, the most hierarchical, most socially stratified, for Pueblo culture.’ It didn’t work, but they tried again with Mesa Verde. When that didn’t work, they rejected hierarchy completely.”
“The biggest change we see in Pueblo history is the abandonment of Mesa Verde and the Four Corners,” Kohler said.
Archaeologists believe the people from Mesa Verde migrated to pueblos along the Northern Rio Grande. These pueblos, some enduring today, have houses that open onto a central plaza, where everyone can see and in some way participate in the religious ceremonies, Bocinksy said.
“They went from a situation where certain people had access to important rituals to one where there was a more equal access,” he said. “That’s a big change.”
Bocinsky sees the same seeds of discontent that prompted pueblos to change their societies playing out in this year’s raucous and surprising presidential election.
“A lot of people still haven’t recovered from the 2008 economic downturn, and we’ve seen a lot of growth in inequality in the last eight years. That’s undermined the credibility of the system,” Bocinsky theorizes. “Support for Trump and Sanders represents that discontent.”
Bocinksy said leaders and policymakers in the Southwest need to consider “the pernicious nature of inequality, combined with climate change, to destabilize societies.”
It’s happened before.
Bocinsky and Kohler collaborated on their paper with Jonathan Rush of the National Center for Super Computing Applications at the University of Illinois at Urbana-Champaign and Keith Kintigh of the School of Human Evolution and Social Change at Arizona State University.
Contact Staci Matlock at 505-986-3055 or [email protected] Follow her on Twitter @StaciMatlock.