[Washington Post]
By Rachel Feltman
When the first humans made their homes at high altitude, they may have had barley to thank. According to research published Thursday in Science, it was probably the introduction of frost-resistant western crops that allowed early Tibetans to survive at about 8,200 feet.
There’s evidence of human presence on the Tibetan Plateau — called ‘roof of the world’ some 20,000 years ago. But people didn’t start settling down there until just 5,200 years ago. Until then, it seems, permanent homes trickled off at 8,200 feet above sea level.
But then something changed, and communities moved on up.
By analyzing the charred seeds left behind by these early Tibetans, the researchers think they’ve found the key to life on the roof of the world: Barley.
“The key to their movement is that crops from very different parts of Asia were coming together at that time,” said study author Martin Jones, a professor of archaeology at the University of Cambridge. “There was a sort of reshuffling of old crops with alien ones. They added a new ingredient to their farming tool kit.”
As Tibetans moved upland, they gradually relied less and less on their traditional staple of millet and switched to barley, which is still an important cereal for contemporary Tibetans. They also started keeping sheep, which were brought to the area from further west.
And that was an absolutely vital shift. Millet couldn’t hold up to the frosts common at 11,000 feet, where barley-growers were able to settle. “What was really important was getting those core calories,” Jones said.
Tibetans weren’t the only early humans benefiting from trans-continental crop swapping at the time. Barley and wheat moved east, and rice made its way to India. Crops from Africa made the rounds as well.
But cereal crops aren’t enough to sustain life at 11,000 feet. Humans needed to adapt at the genetic level, too — but this change probably happened much earlier.
“Anyone can go live for awhile up at that altitude, but the low oxygen causes a lot of problems for pregnant women and infants, so populations won’t grow unless people have these adaptations,” study co-author Loukas Barton, assistant professor at the University of Pittsburgh, said.
There’s some evidence that humans first acquired these genes, which can be found in modern-day Tibetans, tens of thousands of years ago. But for a long time, they still lived on the margins — not at the dizzying heights where their descendants now thrive. Barton and his colleagues believe that frost-resistant crops were what they had to wait for.
Another interesting aspect of the upward move is that it happened just as temperatures were dropping in the region.
“Obviously one of the main challenges of going up is that it’s colder there,” Jones said. “But ironically, it happened at a time when the climate was cooling.”
It may be that as things got harsher all over the region, those who were able to decided to stake out new claims.
“Although you can’t exactly argue that the lowlands were so full there was no space, you can argue that society was changing and breaking off into different kinds of communities,” Jones said. “They were differentiating themselves. The ownership of land and resources was key.”
Today, the world relies almost entirely on three cereal crops — wheat, rice, and corn. But we have a lot to learn about the myriad of crops that allowed our ancestors to survive in new and strange environments, Jones said.
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