Looks like the climate in that area changed radically over the last 4,000 years.
Yes, very much. There are graveyards in the area that have large concentric circles of tree logs planted upright. There were many trees there at one time. These valleys leading into the Tarim basin were fed by streams from the melting glaciers that had accumulated during the Ice Age...when the glacier ice ran out, this whole area dessicated, even the large lakes that were there. The people must have had to move on...Mongoloid skeletons began appearing in the area around 100-200BC...and then mixtures. There were still pure Caucasian grave sites in the area all the way up to the 1300's AD.
Lots of salt left in the area and I do make note that the European Celts were settled around a lot of the salt mining areas in Europe.