Few facts to consider. First, the dee butter is the most important commodity among nomads. Most of Tibetan nomadic population of high-altitude Plato still live out of Yak herds and caravan trade, not agriculture, unlike fertile western provinces.

Second, there is much more influence in traditional households from closely related tribes of neighboring Nepal and Sikkim and Bhutan (Sherpa, Lepcha, Tamang, Bhutia) than from Ladakh or Chinese mainland, so it is more reasonable to think of Nepalese/Indian influence.

Third, there were more trade and migration with Nepal and North India than China or Kashmir. Some caravan routes ran there, of course, but they were not that busy as those to Kathmandu, Sikkim or Bhutan.

You could see that most of heritage buildings in Lhasa has been decorated by Nepalese craftsmen and artists.

'North India', 'Nepal' and the like are reasonably clear locations based on modern states but China and Tibet's relationship to it is less clear in what you say, both for its current status (let's not forget most of historic Tibet is not in the Tibetan Autonomous Region) and history of shifting borders and smaller states.

> Yet there are traces of human life there dating back at least 20,000 years BP (Before Present, Present being defined as January 1, 1950, as used in radiocarbon dating).

What's wrong with writing '20,000 years ago'? Seriously, 'BP' instead of 'ago'‽

Because the real present is constantly moving. To prevent confusion several sciences use 1950 as the present, so if somebody quotes an article where something is radiocarbon dated as 80 years BP, you don't then have to look up the age of the article.

'Western' is a bit of a stretch ... Wild barley (H. vulgare ssp. spontaneum) ranges from North Africa and Crete in the west, to Tibet in the east.