Beijing: Early Tibetans' ability to grow barley enabled them to establish permanent settlements at such an extreme altitude in the Himalayas, a new study suggests. 

Researchers 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 study by the McDonald Institute of Archaeological Research at the University of Cambridge found evidence of periodic human presence as far as 20,000 years ago, Tech Times reported.

They also found signs that around 5,200 years ago, people 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 that would not have thrived at higher altitudes.

However, about 3,600 years ago, people started making permanent settlement at higher altitudes reaching over 3,000 meters above sea level and this happened after barley was introduced to the settlers of this region.

Barley agriculture could provide people enough food supplies even during winter, as barley is frost hardy and cold tolerant, it grows very well on the Tibetan Plateau even today, researchers said.

The research was published in the journal Science.