Earlier Origin of Southwest Farmers

Large farming villages with stone terraces may have been established in the southwestern United States and northern Mexico 3000 years ago, much earlier than previously thought. A prehistoric northern Mexican village, described in tomorrow's Science (p. 1661), dates roughly to the time corn is thought to have been domesticated in the region and upsets notions about the transitions from hunter-gathering to agriculture.

Most archaeologists believe that wandering hunter-gatherers would have only settled down after finding a food source they could depend on year after year. Usually this means growing crops, such as squash and corn, bred to produce consistent yield and large seeds or fruits. The first evidence of domesticated corn farming appeared in the American Southwest and northern Mexico about 3000 years ago, and since all evidence of large, settled villages dated at least 1500 years after that, archaeologists assumed that the conversion from hunter-gathering to agriculture was gradual.

The village that appears to contradict this, called Cerro Juanaqueña in Chihuahua, Mexico, covers more than 10 hectares of a hilltop and is ringed by terraced rock walls. When archaeologists John Roney of the Bureau of Land Management in Albuquerque, New Mexico, and Robert Hard of the University of Texas in San Antonio excavated the site, they retrieved numerous spear points, grinding stones, and other artifacts. Radiocarbon dating revealed that four samples of burnt corn cob were roughly 3000 years old, suggesting that the extensive dwellings and fortifications may have been built soon after corn was introduced, or perhaps earlier. "No one would have expected anything like this until a thousand years later," Roney says.

The finding will be "provocative," predicts Bruce Smith of the National Museum of Natural History in Washington, D.C. The big question, he says, is how these people supported themselves in large communities before corn arrived. One possibility might have been cultivating local plants, such as amaranth and wild gourds, he says.