[Cronos]

"That whole Xinjiang Uygur Autonomus Region is covered with Caucasian skeletons and mummies that date to 2,000BC. The Chinese skeletons and mummies do not start to show up in that region until about 100BC."

To put it bluntly, Xinjiang is not really part of China and neither is Tibet -- China ends at the Gobi desert -- the natural range that kept the Mongoloid race separate from the Caucasian race -- just as the Sahara separated the Caucasians from the Afroids.

Xinjiang belongs to Central Asia, a place where Iranic and Indic tribes were known to have roamed for millennia. Then, around the time of Christ, these were pushed westwards by the Turkic-Mongoloid peoples, as best demonstrated in Afghanistan-Iran:

In Afghanistan, the Turkic peoples moved quickly westwards and separated the Irani speaking Tajiks from Iran. Then, the Mongols came and moved directly south and became the Hazara tribes now found in central Afghanistan, some of which moved further south and formed the Moghul (Mongol) dynasty in India. The Turkic peoples meanwhile moved west to Anatolia.

[blam]

"Xinjiang belongs to Central Asia, a place where Iranic and Indic tribes were known to have roamed for millennia. "

These 'Celtic-like' people were in the area prior to any Iranian or Indian tribes, they did come later though.