The Tibetan Plateau in Asia is not exactly the place many people would like to call their home. With elevation exceeding 4,500 meters, "the Roof of the World," is characterized by freezing temperatures, low oxygen condition and ruthless winds.

No matter the harsh conditions the Tibetan Plateau has, archeologists have evidence that nomadic hunter-gatherers have lived there seasonally and later on even year-round and the first people who successfully survived in this remote land likely had barley to thank for.

Findings of a new research published in the journal Science on Thursday, Nov. 20, suggest that it was probably the early Tibetans' ability to grow barley, a frost-resistant western crop, that enabled them to establish permanent settlements at such an extreme altitude.

For the study, Martin Jones, an archeologist from the McDonald Institute of Archaeological Research at the University of Cambridge in the UK, and colleagues examined pottery, stone artifacts, animal bones, charred plant remains and other signs of human habitation from 53 sites across the northeastern Tibetan Plateau to learn how humans managed to live at high altitudes.

The researchers found evidence of periodic human presence as far as 20,000 years ago. They also found signs that around 5,200 years ago, people have started to establish year-round settlements at up to 2,500 meters above sea level with the early settlers depending on millet, a frost-sensitive grain long planted across northern China that would not have thrived at higher altitudes. Thus, farming is limited to 2,500 meters and below.

About 3600 years ago, however, people started making permanent settlement at higher altitudes reaching above 3,000 meters above sea level and this happened after barley was introduced to the settlers of this region. At around this time, barley started to show up all over the Tibetan Plateau.

"As barley is frost hardy and cold tolerant, it grows very well on the Tibetan Plateau even today. Therefore, barley agriculture could provide people enough - and sustained - food supplies even during wintertime," said study researcher Dongju Zhang, from the Lanzhou University in China.

Those who lived at lower elevations added barley to their millet diet but the farmers who lived at higher altitudes seemed to have abandoned millet and completely relied on barley.

"Since 3600 calendar years before the present, a novel agropastoral economy facilitated year-round living at higher altitudes," the researchers wrote. "This successful subsistence strategy facilitated the adaptation of farmers-herders to the challenges of global temperature decline during the late Holocene."

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