Early inhabitants of the Tibetan Plateau, one of the least hospitable places on earth, survived largely by consuming large amounts of dairy products, according to a new study that has cut ancient teeth.
Sometimes called the Third Pole of the World, the Tibetan Plateau is surrounded by dry, cold and unpredictable conditions that would have made life difficult for the people who lived there some 3,600 years ago. The conditions would hamper efforts to cultivate crops such as barley grown in the warmer Tibetan valleys and lowlands. And they would drop oxygen levels enough to cause potentially fatal hypoxia.
To survive at the Third Pole, the third snowiest place on earth after the North and South Poles, early Tibetans developed a genetic resistance to high altitude. They also turned to goats and sheep and potentially yaks, according to a a new studyanimals that had the power to turn the harsh grasslands of the plateau into life-sustaining milk.
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An ancient dairy
The world history of dairy products goes back thousands of years: cultivation first spread from Asia Minor to Europe about 8,000 years ago and to Mongolia about 5,000 years ago. This new study peered back to about 3,600 years ago by analyzing the dental remains of 40 people from 15 different sites and found clear evidence of milk consumption.
How can researchers tell? Not from the strength of their teeth, but from the tartar attached to them. More commonly known as tartar, calculus is “hard, calcified deposit” formed from a plaque that is actually so durable that it can survive thousands of years buried in the ground.
To learn what these ancient people chewed on while they were alive, the researchers cut away the tartar with razor blades and analyzed the proteins preserved inside using the burgeoning field of proteomics. Of nine high-altitude sites, they found seven with intact oral proteins, and six of them contained milk proteins.
Almost half (47 percent) of the individuals found at the seven sites contained the proteins, as opposed to the lower, more tractable sites. There, the researchers found no evidence of dairy consumption, suggesting that the inhabitants relied more on agriculture. (This does not necessarily mean that these farmers lived without dairy products; they may simply have consumed fewer products.)
Protein patterns
“We were thrilled to observe an incredibly clear pattern,” Li Tang, archaeologist and lead author of the study, said in a press release. “All of our milk peptides come from ancient individuals in the western and northern steppes, where growing crops is extremely difficult. However, we did not detect any milk proteins from the south central and southeast valley, where there is more arable land.”
Further analysis found that the milk came from goats, sheep and potentially yaks, which produce particularly nutritious milk. Modern pastoralists rely on them for the production of butter, cheese and yogurt, but rarely meat. Today, grasslands still account for 68 percent of the Tibetan Plateau, compared to 1 percent devoted to agricultural land.