The introduction of barley agriculture dating back 3,600 years, which suggests it was crucial to the facilitation of human's permanent settlement in the Tibet Plateau, was recently proved to be realized by the migration of millet farming populations from northern China.

Archaeological evidence shows that millet farming populations settled in the lower altitudes of the northeastern part of the Tibet Plateau between 5,200 to 3,600 years ago before barley farming spread to higher elevations. At the end of this stage, barley was adopted by the millet farmers, according to Li Yuchun with the Kunming Institute of Zoology, Chinese Academy of Sciences, first author of the research paper.

Based on the evidence, the research team speculated that millet farming populations may have introduced barley to higher altitudes after they adopted it at lower altitudes.

To test this hypothesis, the team analyzed DNA from 8,277 Tibetans and 58,514 individuals from surrounding populations to find two genetic components well matching the dispersal history of millet farming, said Dong Guanghui, a professor of Lanzhou University and one of the researchers.

These two genetic components were also found in the DNA of neolithic millet farming populations in northern China, indicating the genetic legacy from the neolithic millet farmers to modern Tibetans.

The human migration epic along with the spread of barley farming has been at last recreated by the researchers. The millet farming populations brought barley to the Tibet Plateau and made an important contribution to the Tibetan gene pool.

The research was published in the journal National Science Review.