In a bleak, treeless landscape high in the southern Peruvian Andes, bands of intrepid Ice Age people hunkered down in rudimentary dwellings and withstood frigid weather, thin air and other hardships.

Scientists on Thursday described the world’s highest known Ice Age settlements, two archaeological sites about 4.5 kilometres above sea level and about 12,000 years old packed with artefacts including a rock shelter, stone tools, animal bones, food remnants and primitive artwork.

“What this tells us is that hunter-gatherers were capable of colonising a very extreme environment, the high Andes, despite the challenges at the end of the Ice Age,” said archaeologist Kurt Rademaker of Germany’s University of Tübingen, who led the study published in the journal Science.

The sites in a locale called the Pucuncho Basin were occupied by small numbers of people, probably only in the dozens.

“Bands of hunter-gatherers are small and not many could fit into the rock shelter, perhaps just a few families,” said University of Maine archaeologist Dan Sandweiss, another of the researchers.

The researchers said the sites show high-altitude human habitation was occurring nearly a millennium earlier than previously known.

“Whatever reason they initially went up there, there were reasons to stay despite the challenges,” Rademaker said.

At that altitude, temperatures averaged 3˚C, solar radiation was high and oxygen was low. But there also were animals like vicuña and guanaco – llama relatives – and taruca deer to hunt, the rock shelter, water in streams, bogs and wetlands, and stone like obsidian to make tools.

The tools included spear points, scrapers for working animal hides and implements for cutting and butchering.

The ceilings of the natural rock shelters were blackened with soot from fires. The researchers found an abundance of animal bones as well as starchy tubers that apparently were gathered from lower elevations in Cuncaicha.

An open-air site called Pucuncho, 4,355m above sea level, yielded hundreds of tools.

Some experts think people need to acquire genetic adaptations over many thousands of years to withstand such altitudes. But the fact that people colonised these sites only about 2,000 years after humans first entered South America may suggest otherwise. “We have to re-examine that idea,” Rademaker said.

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