Humans 'on the Tibetan Plateau 3,600 years ago'

People probably moved to the Tibetan highlands 3,600 years ago - an indication of when humans first settled at high altitudes, according to researchers.

Humans were able to settle permanently as high as 3,400 meters on the Tibetan Plateau, which is known as "the roof of the world", by growing altitude-resistant crops and raising livestock, according to a study published in the US journal Science on Thursday.

They survived on wheat and barley imported from the Middle East and on transplants from China such as broomcorn and foxtail millet, said the researchers from China, the United States and Cambridge University in Britain.