The Tibetan people are an ethnic group that is native to Tibet, which is mostly in the People's Republic of China. They number 5.4 million and are the 10th largest ethnic group in the country. Significant Tibetan minorities also live in India, Nepal, and Bhutan. Tibetans speak the Tibetan language, which has many mutually unintelligible dialects. Most Tibetans practice Tibetan Buddhism, though some observe the indigenous Bön and others are Muslims. Tibetan Buddhism influences Tibetan art, drama, and architecture, while the harsh geography of Tibet has produced an adaptive culture of Tibetan medicine and cuisine.
The ability of Tibetan's metabolism to function normally in the oxygen-deficient atmosphere at high altitudes - frequently above 4,400 metres (14,400 ft), has often puzzled observers. Recent research shows that, although Tibetans living at high altitudes have no more oxygen in their blood than other people, they have 10 times more nitric oxide and double the forearm blood flow of low-altitude dwellers. Nitric oxide causes dilation of blood vessels allowing blood to flow more freely to the extremities and aids the release of oxygen to tissues. What is not yet known is whether the high levels of nitric oxide are due to a genetic mutation or whether people from lower altitudes would gradually adapt similarly after living for prolonged periods at high altitudes.
Tibetans traditionally explain their own origins as rooted in the marriage of the monkey Pha Trelgen Changchup Sempa and rock ogress Ma Drag Sinmo. Tibetans who display compassion, moderation, intelligence, and wisdom are said to take after their fathers, while Tibetans who are "red-faced, fond of sinful pursuits, and very stubborn" are said to take after their mothers.