NEW YORK (AP) - A new study says a gene that helps people in Tibet cope with the thin air there came from an extinct relative of humans.
Researchers say they found the Tibetan version of that gene in DNA from Denisovans, a poorly understood group known only from 50,000-year-old fossils in a Siberian cave.
Other studies have found Denisovan DNA in modern populations, but the new study says the Tibetan high-altitude gene is virtually absent outside of Tibet.
Researchers believe the Denisovans passed it on by interbreeding with ancestors of today's humans, but that it remained rare except in people who faced the high altitudes of Tibet. For them, it would confer a survival advantage, which would make it more common over time.