It turns out our ancient ancestors had upward mobility
Scientists have discovered what is by far the oldest evidence of human occupation at extreme altitudes: a rock shelter strewn with bones, tools and hearths 3,000 metres above sea level. People lived at the site, in the mountains of Ethiopia, as long as 47,000 years ago.
The research, reported Aug. 8 in the journal Science, contradicts the longheld view that high elevations were the last places on Earth settled by humans.
That notion was based more on assumptions than hard evidence, it now appears. In East Africa, paleoanthropologists have long focused their attention on the Rift Valley and other archeological sites at lower elevations.
“We were simply the first to go higher,” said Gotz Ossendorf, an archeologist at the University of Cologne in Germany and lead author of the new study.
The high-altitude humans thrived as hunter-gatherers, subsisting on roasted giant mole-rats and glacier-fed streams. They made tools from an outcrop of obsidian. They occupied the rock shelter, off and on, for at least 16,000 years.
Humans have managed to settle into a huge range of habitats. But extreme altitudes pose special challenges. The weather can be brutal, and extreme altitudes don’t support lush forests or grasslands. Low levels of oxygen can be dangerous, sometimes even fatal, to humans at high elevations.
“Our hominid ancestors were born lowlanders,” said Mark Aldenderfer, an archeologist at the University of California, Merced, who was not involved in the new study.
Despite these challenges, people eventually moved uphill. Today, in Ethiopia, the Andes and Tibet, humans live yearround at high elevations. Archeologists have assumed that these places were among the last to be settled.
But in recent years, expeditions to mountains and plateaus have turned up remarkable clues of human occupation tens of thousands of years ago.
To get a deeper understanding of life at high elevations, Ossendorf and his colleagues began a project in the Bale Mountains of southern Ethiopia in 2015.
They travelled more than 1,100 kilometres on foot and with pack horses in search of signs of early human occupation. They visited overhanging cliffs to see if people had ever used them as shelters. The archeologists found 331 rock shelters with signs of human occupation. Almost all had been visited in recent centuries by livestock herders, making it difficult to examine the sites for truly ancient human remains.
But one rock shelter had gone undisturbed, thanks to a low ceiling. When scientists dug into the floor, they turned up hearths, animal bones and tools — evidence that people once lived there.
The tools surprised the researchers, because they were made in the distinctive style of the Middle Stone Age, which lasted from about 28,000 to 300,000 years ago — far older than the researchers had expected.
“That was breathtaking,” Ossendorf recalled.
To establish the age of the site, called Fincha Habera, the team analyzed carbon from charcoal still in the hearths. It ranged from 31,000 to 47,000 years old. The menu was dominated by one entree, the researchers found: giant molerats. The residents may have smoked the animals out of their tunnels.
The Fincha Habera people made a great number of obsidian tools. It is clear that the inhabitants didn’t bring the tools from the lowlands — the researchers traced the rock to an outcrop nearby, at an elevation of over 4,100 metres.
Some researchers have viewed extreme altitudes as refuges of last resort. But at the time that people lived at Fincha Habera, the lowlands were wet and had plenty of game, said Lars Opgenoorth, an ecologist at Philipps University Marburg in Germany and a co-author of the study.
People living in Fincha Habera, he argued, were not fleeing conditions somewhere else. “They thought it was a good place to be,” he speculated.