Excavations at the high-altitude Cuncaicha rock shelter turned up a diverse set of stone tools, large animal bones, campfire soot, and rock art. | Kurt Rademaker
Researchers in the Peruvian Andes have uncovered artifacts from the oldest extremely high-altitude settlements identified to date, according to a study in the 24 October issue of Science.
"There are many sites of this age at lower elevations in the Andes, and of course there are older sites [at lower elevations] elsewhere in the world," said lead author Kurt Rademaker, visiting assistant professor of anthropology at the University of Maine, "but there is nothing this old at this elevation."
The sites are perched at nearly 4,500 meters (2.8 miles) above sea level, in an environment of low oxygen, high solar radiation, and cold temperatures. Researchers are uncertain how early humans survived in such places. Some have hypothesized that people had to genetically adapt to the conditions, a process that likely took many thousands of years. Others say environmental changes, like the recession of glaciers, were necessary to make conditions less hostile for the early settlers.
But at the two sites identified by Rademaker's team, nearby glaciers never invaded, and thus never receded to create an opening for humans to migrate there. What's more, dating of the artifacts found at the sites suggests humans colonized the area within 2,000 years of their initial entry to South America. "This suggests that humans either developed genetic adaptations to high-altitude conditions extremely quickly," Rademaker explained, "or that people colonized high altitudes before genetic adaptations evolved."
His team reported on artifacts from two different settlements inhabited by hunter-gatherers. At the first site, Cuncaicha, they found diverse tools including more than 500 projectiles used as spears or arrows, hand axes, and scrapers. They also found animal bones and starchy roots consumed as food. The researchers believe this site to have been a base camp. The higher altitude site, Pucuncho Basin, was home to a llama relative that roamed on a predictable schedule. It was ideal for hunting, the researchers said.
Large bones at both sites helped the team date these locations to more than 12,000 years old, or the late Pleistocene. Previously, archaeologists studying terrain at altitudes higher than 4,000 meters above sea level had not found evidence of human settlement as far back as the Pleistocene.
Though the challenges of high-elevation living have been invoked to explain this absence, Rademaker and colleagues suggest something else might explain the lack of Pleistocene archaeological sites in high-elevation lands.
"Perhaps people haven't searched for these sites in the right way, or in enough places," said co-author Daniel Sandweiss, professor of anthropology and Quaternary and climate studies at the University of Maine. "Few archaeologists work at such high altitudes."
"High-elevation mountains and plateaus are among the most remote and least archaeologically-studied lands on the planet," Rademaker added, "so we really lack a thorough knowledge of what is there."
Rademaker said that these extreme, challenging environments "also present many opportunities for those equipped to take advantage of them." The Pucuncho Basin, for example, contains abundant freshwater, bogs that support animal prey, rock shelters, rocks for stone tool making, and plants for fuel.
Rademaker said that the possibility that early humans colonized high-altitude regions earlier than thought, and particularly before genetic adaptations evolved, leaves some lingering questions. For instance, when did high-altitude adaptations present among modern highlanders evolve?
"There is a lot left to learn about when and how this happened," he said, "not just in the Andes but in other high-elevation regions, and learning it will tell us more about human evolution."