A gene from a human sub-species that became extinct 40,000 years ago has helped Tibetan people survive the harsh conditions of their Himalayan home, research has shown.

The Denisovan gene is one of five that over thousands of years have equipped Tibetans for life on a high, arid plateau where they cope with low oxygen levels and extreme cold.

Scientists made the discovery after mapping the DNA of 27 Tibetans looking for adaptive genes.

They identified four genes known to aid survival at high altitude and make up for a lack of oxygen, and a fifth which plays a role in vitamin D metabolism.

The Tibetan variant of one high altitude gene, EPAS1, is understood to originate from the Denisovan people who lived in Eurasia until around 40,000 years ago.

Like Neanderthals, the Denisovans were a human sub-species known to have bred with the Homo sapiens ancestors of people living today.

The Tibetan variant of one high altitude gene is understood to originate from the Denisovan people who lived in Eurasia until around 40,000 years ago.

Researcher from the University of San Diego in the US, Dr Tatum Simonson, said: "The comprehensive analysis of whole-genome sequence data from Tibetans provides valuable insights into the genetic factors underlying this population's unique history and adaptive physiology at high altitude.

"This study provides further context for analyses of other permanent high altitude populations, who exhibit characteristics distinct from Tibetans despite similar chronic stresses, as well as lowland populations, in whom hypoxia (low oxygen) related challenges, such as those inherent to cardiopulmonary disease or sleep apnoea, elicit a wide range of unique physiological responses."

The vitamin D gene, VDR, may compensate for vitamin D deficiency which commonly affects Tibetan nomads, said the scientists.

The research is published in the journal Public Library of Science Genetics.