As humans spread across the planet, high-altitude places like the Tibetan Plateau were some of the last regions to be inhabited. Now archaeologists have discovered a cache of ancient stone blades in northern Tibet from at least 30,000 years ago. The find is the earliest evidence for people living at high altitude and means humans were living in the harsh conditions of the miles-high Tibetan Plateau much earlier than previously thought.

“We did not expect to find such early evidence of human occupation,” said John Olsen, an archaeologist at the University of Arizona in Tucson and co-author of the new research.

Missing Link

Before the discovery, researchers thought humans colonized the Tibetan Plateau only 12,000 years ago. After all, year-round cold, little vegetation and scarce oxygen typify the area as one of the world’s most extreme environments. Although genetic studies suggested humans inhabited the region much earlier, perhaps 15,000 to 20,000 years ago, concrete archaeological proof was missing until now.

During an archaeological investigation of the eastern Changtang region in northern Tibet in 2013, Olsen and colleagues came across thousands of stone artifacts at a site called Nwya Devu. Located about 15,000 feet above sea level, it sits just south of two large lakes and less than 200 miles northwest of Lhasa, the capital of the Tibet Autonomous Region. The team returned for an extended excavation from 2016 to 2018.

Old Stone

In an area equal to about 65 feet by 65 feet and approximately five and a half feet deep, the archaeologists found a trove of blades, flakes and tools. All together, the team unearthed more than 3,600 stone artifacts, they report today in the journal Science. And all the artifacts were made of black slate from an outcrop less than half a mile from the excavation site.

It’s an indication that humans were using technology to adapt to the harsh conditions earlier than scientists thought, and another reminder that humans migrations encompassed a broad range of environments.

The researchers dated the sediments from the dig site using a method that estimates when the dirt was last exposed to sunlight called optically stimulated luminescence. They found the deepest layer dates to between 45 and 30 thousand years ago.

The team has not yet found any bones at the site, which would provide direct evidence for people there. But because they found so many tools in such close proximity to a source of raw materials, the researchers conclude the site was once a workshop. Foragers may have made seasonal use of the area to acquire resources and possibly to hunt.

“Our research indicates that human ancestors were technologically capable of accommodating high altitudes much earlier than we previously had evidence for,” Olsen said.