The Anasazi of the Chaco Culture Violently Clashed With Mesa Verde

It's a given that, in numbers terms, the 20th Century was the most violent in history, with civil war, purges and two World Wars killing as many as 200 million people.

But on a per-capita basis, Washington State University archaeologist Tim Kohler has documented a particularly bloody period more than eight centuries ago on what is now American soil. Between 1140 and 1180, in the central Mesa Verde of southwest Colorado, four relatively peaceful centuries of pueblo living devolved into several decades of violence.

Writing in the journal American Antiquity, Kohler and his colleagues at WSU and at the University of Colorado-Boulder document how nearly nine out of ten sets of human remains from that period had trauma from blows to either their heads or parts of their arms.

"If we're identifying that much trauma, many were dying a violent death," said Kohler, whose study was funded by the National Science Foundation.

Yet at the same time, in the northern Rio Grande region of what is now New Mexico, people had far less violence while experiencing similar growth and, ostensibly, population pressures. Viewed together, said Kohler, the two areas offer a view into what motivates violence in some societies but not others. The study also offers more clues to the mysterious depopulation of the northern Southwest, from a population of about 40,000 people in the mid-1200s to none 30 years later.

From the days they first arrived in the Southwest in the 1800s, anthropologists and archaeologists have for the most part downplayed evidence of violent conflict among the early farmers in the region. A minority raised the specter of violence but lacked a good measure for it.

"Archaeologists with one or two exceptions have not tried to develop an objective metric of levels of violence through time," said Kohler. "They've looked at a mix of various things like burned structures, defensive site locations and so forth, but it's very difficult to distill an estimate of levels of violence from such things. We've concentrated on one thing, and that is trauma, especially to the head and portions of the arms. That's allowed us to look at levels of violence through time in a comparative way."

Meanwhile, Kohler and his colleagues are examining the role of factors like maize production, changes to the climate, and growing population in changing levels of violence. A paper of his published in June in the Proceedings of the National Academy of Sciences found that the Southwest had a baby boom between 500 and 1300 that likely exceeded any population spurt on earth today.

Both the central Mesa Verde and northern Rio Grande experienced population booms, said Kohler, but surprisingly, the central Mesa Verde got more violent while the northern Rio Grande grew less so.

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