The earliest (known) contacts were via the cinnamon routes. It was a long LONG time ago. Its not inconcievable that someone, probably many actually, travelled back to China and just stayed.
I think you're missing the point completely. These people lived there for thousands of years...they lived there for 2,000 (or more) years before any Chinese appeared in the region. There are whole villages, graveyards, dessicated fruit groves, etc. They weren't just passing through. Then there came a severe climate change and the streams and lakes dried up.
That's consistent with an older view, that of diffusion of discoveries (writing, the plow, the stirrup, the abacus, gunpowder, what-have-you) from point of origin (wherever each one originated) outward to the rest of the world.Rethinking a History That's Carved in StoneThree months after the announcement of its discovery in Central Asia, a tiny stone object inscribed with symbols thought to be the writing of an obscure desert culture from 4,000 years ago is more of an enigma than ever. If this is indeed an early form of writing, as its discoverer has suggested, it is strong evidence for a previously unknown civilization that began about 2300 B.C. across much of modern Turkmenistan and parts of Uzbekistan and Afghanistan... An even more puzzling aspect of the discovery has been raised by specialists in ancient Chinese writing. They contend that the inscription bears more than a passing resemblance to Chinese writing -- not an early script, but one that was not used until about 200 B.C... There is no clear evidence for Chinese writing before about 1300 or 1200 B.C. -- 1,000 years after people lived at the Anau site in Turkmenistan where the mysterious inscription was unearthed... Another possibility, which would throw the scholarship of Chinese writing into turmoil, is that the 2300 inscription date is correct. That would suggest that influences from Central Asia or farther west might have contributed to the invention of Chinese writing. Dr. Mair, who holds that such influences were greater than previously thought, has raised this controversial point.
by John Noble Wilford
July 31, 2001
Origins of the Bronze Age
Oasis Civilization in Central Asia
by Fredrik T. Hiebert