Recent research into the ability of Tibetans' metabolism to function normally in the oxygen-deficient atmosphere above shows that, although Tibetans living at high altitudes have no more oxygen in their blood than other people, they have ten times more nitric oxide and double the forearm blood flow of low-altitude dwellers. Tibetans inherited this adaptation thanks to their Denisovan admixture. Nitric oxide causes dilation of blood vessels, allowing blood to flow more freely to the extremities and aids the release of oxygen to tissues.