Stone Age Cave at 11,000 Feet Is Oldest High Altitude Human Settlement Ever Discovered

Over 30,000 years ago, Stone Age people in Ethiopia had moved into the mountains of Ethiopia, setting up a base in a rock shelter 11,000 feet above sea level. This is the earliest evidence of prehistoric people living at high altitudes, archaeologists that uncovered the site say.

High altitudes place many stresses on the human body. The lower oxygen levels make breathing harder, UV levels are higher and temperature fluctuations are greater. As a result, it was generally thought people did not start living in the mountains until relatively recently in human history.

In 2014, however, scientists announced the discovery of a settlement in the Andes that dated back 12,000 years. This was the oldest evidence of high-altitude living ever discovered, raising questions about how and when humans adapted to these extreme conditions.

Now, in a study published in Science, researchers led by Götz Ossendorf from the Institute of Prehistoric Archaeology at the University of Cologne, Germany, have found a site that shows signs of human occupation between 47,000 and 31,000 years ago.

In an expedition to the Bale Mountains, researchers found a rock shelter containing thousands of artifacts from the Middle Stone Age. This included tools, hearths of fires and animal bones—evidence suggesting the prehistoric people that stayed at the site ate giant mole rats and made good use of the nearby resources.

Radiocarbon dating showed the shelter dated far beyond any other high altitude archaeological site.

The people at the Bale Mountain site would have been hunter-gatherers. Ossendorf told Newsweek it is not surprising to find evidence of humans in these extreme regions—to access food they would have traveled far and wide regularly, and never stayed at a single site for very long. They likely returned to different sites following an annual cycle, he said.

"We know of even older high-altitude occupations in Tibet [by Denisova hominins 160,000 years ago] and human presence in high altitudes at probably the same time in Ethiopia. But these previous records only showed the mere presence of humans at a given time, there is no additional information on what people did," he told Newsweek in an email. "What we could demonstrate now is that people stayed there for longer periods and actively used the resources of the afro-alpine ecosystem, and they did this repeatedly between 47,000 and 31,000 years ago (we cannot be more precise)."

The site appears to have been used repeatedly over the course of several thousand years.

Initially, the researchers thought maybe these prehistoric people had ventured into the mountains because drought in the lowlands had forced them to seek out new habitats. However, analysis of the climate at the time revealed this was not the case.

"Conditions were humid at the time of high-altitude occupation, even in the lowlands and people must have lived in the lowlands and in the high altitudes at the same time in Ethiopia," Ossendorf said. "We found an ostrich (never occurring in these altitudes) eggshell fragment in our Middle Stone Age deposits, which is a clear sign that people had contacts and networks with the lowland people and were not isolated or fragmented."

So why did they make their way into the mountains? "To cut a long story short," Ossendorf said, "we don't know, but think it was curiosity that moved the people into these elevations."