I was travelling with my wife and we had no problem with altitude sickness. The other people in the carriage were Chinese and some were badly affected. A couple from Beijing needed medical attention and were advised to return to a lower altitude and acclimatise before proceeding further.
All of Tibet is at high altitude and getting higher. Deep down, the entire region is part of India, which was once part of Gondwanaland – together with Australia, Antarctica, Africa and South America. When this vast southern continent broke up, the Indian bit headed north at great speed (geologically speaking) and collided with Eurasia.
The undersea part of the Indian tectonic plate ducked down and pushed its way beneath the Eurasian plate which was uplifted to form the highland we call Tibet. If you have difficulty visualising this process then think of a raft being pushed under another raft. The continents are like rafts drifting in a sea of molten magma.
The Indian subcontinent followed behind the undersea part of the Indian plate and made contact with Eurasia about 45 million years ago. It was too light to go under and a bit of a mess ensued. The outcome was the range of mountains we call the Himalayas.
Most of the Tibetan people live in the “lowlands” adjacent to the Brahmaputra valley, which runs along the northern edge of the Himalayas before crossing down into India. The huge sand dunes in the valley date from when the land was below sea level. The Chinese are planting trees to stabilise the dunes. A Tibetan commented to me that, since the country is continually rising, there is not much to worry about. She figured you would need an awful amount of erosion to wash Tibet into the Bay of Bengal. That’s an interesting observation but unlikely to carry weight with the conservationists.
Scarcely any part of Tibet is less than 3000 metres (10,000ft) above sea level. When you talk about “lowland” that’s what you mean. The Tibetans have been in Tibet for 3000 years and have adapted to the high altitude. DNA studies show they carry a gene that enables them to make efficient use of the depleted oxygen in the thin air.
A period of 3000 years corresponds to about 100 generations so it seems this is more than sufficient for the adaptation to occur. People who carry the favourable gene presumably have an advantage over those that don’t. They raise more children and the gene spreads through the population.
The Tibetan’s are a light skinned people with an amazing ability to produce melanin. On a trip into the highlands with my friend Kangi, I met herdsmen with faces tanned black by the high-altitude sun. They were so dark I thought they came from southern India. Later, when we went down to a stream to wash, they displayed skin tones not much different from my European pallor. I guess an ability to take an impressive tan is another favourable adaptation.
The Tibetans were once fierce warriors who terrorised their neighbours with a ferocity that put them in the same league at the Mongol hordes. Then they found Buddha and adopted his teachings. They are now pacifists. Monasteries dot the land and many young men spend time as monks before joining the workforce – somewhat as other young men attend university.