Barley helped prehistoric humans conquer 'roof of the world': study

Growing frost-resistant crops, particularly barley, enabled humans to establish permanent settlements at high altitudes on the Tibetan Plateau, also known as the "roof of the world," about 3,600 years ago, researchers from China, Britain and the US said Thursday.

The researchers reported in the U.S. journal Science that they studied artifacts, animal bones and plant remains from 53 sites across the northeastern Tibetan Plateau in order to paint a picture of early human settlement in the region.

Despite evidence of an intermittent human presence there dating back to at least 20,000 years ago, the first villages were established only by 5,200 years ago, co-corresponding author Dong Guanghui of Lanzhou University in China said in an email.

That's because a longstanding tradition of millet farming that had become widely established along the middle and lower reaches of the Yellow River extended upstream into the northeastern Tibetan Plateau.

But due to the frost sensitivity of millet crops, such as foxtail millet and broomcorn millet, the earliest of those settlements were only limited to altitudes less than 2,500 meters, he said.

Then, barley and wheat, the principal cereals of the so-called Fertile Crescent, a region that covered modern day Iraq, Jordan, Syria and Israel, were introduced to this region along with domesticated sheep about 4,000 years ago.

The importation of western cereals, particularly the cold tolerant barley, as well as sheep, enabled humans to adapt to the harsher conditions of higher altitudes in the Tibetan Plateau, leading to the establishment of permanent settlements above 3,000 meters about 3,600 years ago, Dong said.

Interestingly, the human expansion into the higher, colder altitudes took place as the world was becoming colder, the researchers said.

As the temperature drops, there may be insufficient food resources, Dong explained, saying that "as a result people need to adopt new technologies to increase productivity or some of them move to other sparsely populated areas."

The study also included researchers from the University of Cambridge, University of Pittsburgh, Washington University in St. Louis, Qinghai Provincial Institute of Cultural Relics and Archaeology, Chinese Academy of Social Sciences and Peking University.