People Lived On The Roof Of The World In The Ice Age

These tools are evidence of the earliest known high-altitude human presence, deep in the Ice Age. Xing Gao

Tibet today is not an easy place to live. Military occupation aside, the so-called “third pole” is cold, dry, and the air is almost unbearably thin. Yet for the first time, we have evidence people lived there 30,000-40,000 years ago, when conditions must have been much worse.

Until the publication today of a paper in Science, no signs of human habitation had been reported on the Tibetan Plateau prior to the start of the Holocene era, more than 11,000 years ago. Some older sites had been found around the Plateau's edges, but nothing was known above 4,000 meters (13,000 feet). Nevertheless, the fact that genes inherited from Denisovans give Tibetans part of their altitude adaptation hinted at humans inhabiting the area considerably earlier.

This hypothesis has been confirmed, with the discovery of evidence of human presence at Nwya Devu, 4,600 meters (15,000 feet) above sea level.

Evidence for ancient human occupation at Nwya Devu, north-west of Lhasa, was first found in 2013 in the form of black slate artifacts. Their true age is much harder to determine, however. Now a team led by Dr Xing Gao of the Chinese Academy of Sciences have dug into sediments at the site to change that.

Living in Tibet doesn't offer a lot of oxygen or food options, so maybe it was the view that brought people there 40,000 years ago. John Olsen

More than 3,000 black slate artifacts were found in the dig, including blades, scrapers, and the cores from all quarried from a nearby hill, making Gao and co-authors suspect the site was a tool-working factory. The tools resemble those found at a few sites in North China but are different in design from those found anywhere else in the world.

Using optically stimulated luminescence techniques, dates were measured for 24 items from the site. Those found closest to the surface, in what Gao and colleagues call Layer 1, were found to be 4,000-13,000 years old, values confirmed using Carbon 14 dating of freshwater mollusk shells from the bottom of Layer 1.

The layer below produced age estimates of 18,000-25,000 years ago, coinciding with the peak of the last glacial period when the Earth was as cold as it has been for a long time. Beneath this, yet another layer was dated to somewhere between 30,000 and 45,000 years ago. This was also confirmed using radiocarbon dating of shells.

It seems people lived at Nwya Devu for long periods of time, quite possibly continuously, when it was even colder and probably more barren than it is today. What drew them there is a mystery, as is whether the first arrivals were Denisovan or Homo sapiens, but the occupation is far older than any in the Andes, making this easily the oldest high-altitude evidence of human occupation.

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