Very interesting.
Mair said that during his searches dealing with the Tarim Mummies they came across human artifacts dated to 250,000 years ago in that region. (he just mentioned this in passing in his book)
About 25,000 B.C. there appears in North China a new human type, found in upper layers in the same caves that sheltered Peking Man. This type is beyond doubt not Mongoloid, and may have been allied to the Ainu, a non-Mongol race still living in northern Japan. These, too, were a palaeolithic people, though some of their implements show technical advance. Later they disappear, probably because they were absorbed into various populations of central and northern Asia. Remains of them have been found in badly explored graves in northern Korea.
4 The Neolithic age
In the period that now followed, northern China must have gradually become arid, and the formation of loess seems to have steadily advanced. There is once more a great gap in our knowledge until, about 4000 B.C., we can trace in North China a purely Mongoloid people with a neolithic culture.