[LINK] Scientific American on the disappearance of the Mesa Verde

[rfmcdonald]

The article "The Greatest Vanishing Act in Prehistoric America", by Richard Monastersky and Nature, looks at the latest findings on the disappearance of the Mesa Verde people--known also as the Anasazi--in the 13th century. What happened to this dense population?

Vultures carve lazy circles in the sky as a stream of tourists marches down a walkway into Colorado's Spruce Canyon. Watching their steps, the visitors file along a series of switchbacks leading to one of the more improbable villages in North America—a warren of living quarters, storage rooms, defensive towers and ceremonial spaces all tucked into a large cleft in the face of a cliff.

When ancient farmers built these structures around the year 1200, they had nothing like the modern machinery that constructed the tourist walkway. Instead, the residents had to haul thousands of tonnes of sandstone blocks, cut timber and other materials down precarious paths to build the settlement, known as Spruce Tree House, in Mesa Verde National Park.

“Why would people live here? That's an important question. It's not an easy place to reach,” says Donna Glowacki, an archaeologist now at the University of Notre Dame in Indiana, as she walks among the ruins. Even more perplexing is what happened after they settled there. The villagers occupied their cliffside houses for just a short time before everyone suddenly picked up and left. So did all the other farmers living in the Four Corners region of the American Southwest, where the modern states of Colorado, New Mexico, Utah and Arizona meet (see 'Turbulent times').

All together, nearly 30,000 people disappeared from this area between the mid-1200s and 1285, making it one of the greatest vanishing acts documented in human history. What had been one of the most populous parts of North America became almost instantly a ghost land.

Archaeologists have long puzzled over what drove these farmers, the ancestors of the Pueblo people, from their homes and fields. “That is one of the iconic problems of southwestern—and world—prehistory,” says archaeologist Mark Varien, who is executive vice-president of the Crow Canyon Research Institute in Cortez, Colorado. Early scholars blamed nomads, the ancestors of the Apache and Navajo, for violently displacing the farmers. Over the past couple of decades, the main explanation has shifted to climate—a profound drought and cold snap that hit in the 1270s.

But a series of studies by Glowacki, Varian and other researchers reveals a much more complex answer. The scientists have used detailed archaeological analysis, fine-grained climatic reconstructions and computer models to simulate how ancestral Pueblo families would have responded to their environment. The interdisciplinary strategy has enabled the researchers to examine prehistoric societal changes at a level unattainable in most other regions. “We have enormous detail on this archaeologically. Unparalleled detail,” says Steve Lekson, an archaeologist at the University of Colorado Boulder.