Study identifies seven new loci associated with high-altitude living.

Tibetan populations have evolved at least nine specific genetic variants to help them survive the extreme conditions of the Tibetan Plateau. Living permanently at over 4,000 m above sea level, these populations have been coping for millennia with 40% less oxygen and 30% stronger UV radiation, as well as exposure and limited food.

In the largest genetic study of Tibetan people to date, Jian Yang and colleagues identified nine genes associated with recent natural selection. They compared whole-genome sequences of 3008 Tibetans and 7278 non-Tibetans, and found seven previously unidentified genes associated with recent positive natural selection in Tibetan populations. They also confirmed the signal of recent selection for two known genes.

These nine genetic variants are correlated with an increased red blood cell count and higher haemoglobin production – necessarily to cope with low-oxygen environments; as well as increased foliate production – useful to deal with high levels of UV radiation.

Using the data, the authors also calculated the most accurate estimate yet of when the Tibetan and Han populations diverged, which has remained uncertain. By their estimate, the Han and Tibetan populations split 4725 years ago, and the Yi, Tu, and Naxi populations are genetically intermediate between them.

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