Archaeologists have long thought that high-altitude zones, where the air is thin, the weather harsh, and the campfire fuel sparse, were among the last spots to be settled by people. Human beings, the theories go, made their way into deserts and even the Arctic before they felt compelled to clamber up above the treeline and make permanent settlements in inhospitable environments that require significant cultural and biological adaptation.
Now, University of Maine researchers are challenging those beliefs.
They announced Thursday the discovery of the highest altitude human settlements from the ice age, dating back to 12,400 years ago in the Peruvian Andes and sitting more than 14,000 feet above sea level. The rock shelter and tool-making work site described in the journal Science were active just a few millennia after people first entered South America, suggesting humans may have adapted to extreme environments more rapidly than most people believed.
“We know climate and environment are changing very rapidly in our world,” said Dan Sandweiss, a professor of anthropology and climate studies at the University of Maine who oversaw the work. “Knowing that people are more adaptable than we thought is perhaps hopeful for people to adapt to changes that are coming. It doesn’t mean we shouldn’t try and slow it down and stop it.”
The discovery of the two sites stemmed from Sandweiss’ work in the 1990s. He was working on a site called Quebrada Jaguay near the Peruvian coast that contained sharp tools made from volcanic glass called obsidian. That material was available only in the nearby highlands.
A graduate student in Sandweiss’ laboratory, Kurt Rademaker, began analyzing the chemical makeup of the obsidian unearthed at Quebrada Jaguay and at various spots in Peru to figure out its likely origin. He used mapping software to find the closest paths between the matching obsidian source and the coastal settlement -- and eventually began the hard work of trekking through the mountains in search of archaeological remains. He discovered a workshop site containing tools that dated back to early as 12,800 years ago and a rock shelter with signs of extensive human habitation and hunting from 12,400 years ago.
Researchers were able to figure out how old the sites were using a combination of techniques, including identification of the characteristic styles of the fluted tools they discovered as well as radiocarbon dating.
The work is sure to stir some controversy. From an archaeological standpoint, it is excellent, according to Mark Aldenderfer, a professor of anthropology at the University of California at Merced. But he isn’t yet convinced of the Maine researchers’ interpretation that these settlements were permanent.
“The real trick about high elevation is not getting there and visiting; it’s actually living there permanently, and that’s what they don’t address,” Aldenderfer said. “I think the [sites] are ephemeral. They might have been used for one, two, three months but at some point they went someplace else.”
Sandweiss said there are contextual clues that suggest these weren’t just temporary camps. The number, type, and extent of tools unearthed, for example, suggest it wasn’t just an outpost that outsourced selected activities. The variety of food remains also support the idea of long-term habitation, he said. However, it is unlikely that the people lived their year-round, given the harsh winters.
The researchers do not know what sort of adaptations -- cultural or biological -- the people who lived at these altitudes would have undergone. The next step will be to find human remains that harbor ancient DNA that could be analyzed to search for evidence of high-altitude genetic adaptations.
For years, genomics researchers have been trying to identify the genetic changes that allow some people to thrive at high altitudes, considered by these researchers to be above 14,000 feet.
Around the world, high-altitude dwellers appear to have undergone “convergent evolution,” meaning that populations in Tibet, Ethiopia, and the Andes independently gained the genetic and physiologic changes that allowed them to live up high, said Sarah Tishkoff, a professor of genetics and biology at the University of Pennsylvania. Researchers who study human evolution are interested in how and how quickly these adaptations occur.
Other traits have evolved quickly. Tishkoff, for example, has traced the emergence, over a span of 3,000 to 6,000 years, of the trait for lactose tolerance among populations that consumed cow’s milk. The hunt for high-altitude adaptations will be more complicated, she said, since the trait is likely controlled by more than one gene.
“It will just be really interesting when we get more data... to be able to date those [genetic adaptations] and see if they correspond with this archaeological data,” Tishkoff said.