Researchers working at the “roof of the world” reveal that it wasn’t until the successful cultivation of frost-hardy cereal grains on the Tibetan Plateau that humans were able to live year-round at dizzying heights of 3,000 meters. The findings, published in Science this week, helps explain when and how humans adapted to living (and farming) in the harsh high-altitudes.
Previous work has identified temporary and intermittent hunter-gatherer settlements on the Tibetan Plateau from as long ago as 20,000 years. But humans only gained a solid foothold there about 5,200 years ago, when the first semi-permanent villages showed up in the archaeological record. It will be at least another millennium before these early settlers would build permanent societies that could survive so high.
A team led by Fahu Chen of Lanzhou University examined animal teeth and bones (mostly sheep, cattle, and pigs), plant remains, and archaeological artifacts from 53 sites spanning over a thousand kilometers across the northeastern Tibetan Plateau. The earliest of these farming settlements, along the Yellow River and its tributaries, were largely sustained by frost-sensitive crops like foxtail millet and broomcorn millet. These farms, dated between 5,200 and 3,600 years ago, approached a maximum elevation of 2,527 meters.
Then, about 3,600 years ago, people whose diets were made up of mostly frost-resistant crops began making their way up to altitudes beyond 3,000 meters -- likely in pursuit of game at first. That’s also around the time when cross-continental crop exchanges brought barley, wheat, and other cold-tolerant grains from the “Fertile Crescent” of the Middle East eastward to the Tibetan Plateau.
"It's a global phenomenon of farmers taking on exotic crops," study author Martin Jones of Cambridge tells New Scientist. "It's basically an expansionist period where people were looking for new options in new, extreme environments." Pictured to the right are carbonized crop remains from agricultural settlements in the Tibetan Plateau. Barley and wheat seeds are on the left, foxtail and broomcorn millet seeds on the right.
Surprisingly, people were moving higher and higher as the planet was getting colder. "Not only did these farmer-herders conquer unheard of heights in terms of raising livestock and growing crops like barley and millet, but that human expansion into the higher, colder altitudes took place as the continental temperatures were becoming colder,” Jones explains in a news release. "Year-round survival at these altitudes must have led to some very challenging conditions indeed -- and this poses further, interesting questions for researchers about the adaptation of humans, livestock and crops to life at such dizzying heights." Here are some thick cultural deposits of the Talitaliha site (Nuomuhong-Bronze Culture) in Qaidam basin:
Images: Martin Jones (top), Xin Jia (middle), Guanghui Dong (bottom)