Paleo-Indian hunters ventured high into the Andes Mountains as early as 12,800 years ago, as much as two thousand years sooner than previously thought.
The finding, reported Thursday in the journal Science, suggests that South America's first inhabitants raced across the continent rather than spreading slowly to its remotest corners.
"It was a land rush, a free-for-all," said study author Kurt Rademaker, an archaeologist at the University of Tubingen in Germany. "People were much more capable and adaptable than we ever thought." (Related: "Ancient South Americans Ate Pachyderms.")
Rademaker discovered evidence of their pioneering abilities high in the arid Peruvian Andes, in a place known today as the Pucuncho Basin. With plenty of water, grass, and vicuñas (a relative of the llama), "it was an oasis in a desert region," he said.
While exploring this alpine oasis, Rademaker found an ancient campsite in a rock alcove, as well as two obsidian quarry sites. A type of volcanic glass, obsidian has long been prized for making sharp-edged tools. It's still used today for surgical scalpels.
Excavation of the sites yielded numerous stone tools, including two "fishtail" arrowheads distinctive to South America's first peoples. Radiocarbon dating of charcoal and animal bones indicated that Paleo-Indian hunters had been using the site as a base camp as early as 12,800 years ago.
Vicuñas and llamas, rather than obsidian, likely attracted hunters to the higher altitudes of the Andes, Rademaker said. Even today, people herd llamas across the 51 square mile (132 square kilometers) Pucuncho Basin.
Most likely the ancient hunters traveled seasonally to the base camp, staying there from March through November while they hunted llamas and deer.
Rademaker's research, supported in part by the National Geographic Society Waitt Grants Program, overturns conventional wisdom that prehistoric people needed long periods of time to genetically adapt to the challenges of living at high altitudes, especially the thin air. Oxygen pressure at the Pucuncho Basin is only 60 percent of its strength at sea level. (Climbers who venture there today spend time acclimatizing.)
"These are some of the highest known examples of human occupation," says anthropologist Tom Dillehay of Vanderbilt University in Nashville, Tennessee. "But it is not a great surprise, because we find people expanded widely wherever we look across South America." (Related: "7 Great Innovators in Archaeology.")
Dillehay points to evidence of ancient human occupation everywhere from Monte Verde in southern Chile (dated to 14,500 to 14,250 years ago) to Quebrada Jaguay on the Peruvian coast. (Related: "Earliest Known American Settlers Harvested Seaweed.")
These and other sites are changing our understanding of when and how quickly humans first populated South America, says archaeologist Claudio Javier Patané Aráoz of Argentina's Universidad Nacional de Córdoba.
"It can be argued strongly that these human groups arrived in the final Pleistocene times, moving and occupying different environments quickly," he noted in an email.
Geologists have shown that the basin was clear of Ice Age glaciers by 15,000 years ago. "Once the ice receded, the grass grew and the animals followed," Dillehay says. "Followed by the hunters, I'm sure."
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