I know I'm making myself tiresome, but there's not much of a story here. The presence of various Caucasian / Middle Eastern peoples from Central Asia in China (as soldiers and traders) has been known from literary sources for a long time. The Sui dynasty is a little bit before the Silk Road became a major factor and before China made its biggest incursions West, but this isn't big surprise.

Genetic material is most valuable when it tells us something different than what we thought we knew -- for example, the Turkish origins of the Etruscans had been only a rumor. The Tokharian discoveries apparently confirmed something that was suspected on the base of language group, but not known for sure. This particular find isn't as exciting.

60 years ago Boodberg (talking of language groups mostly) hypothesized that Central Asia was first Sinitic (ca. 1000 BC), next Indo-European (Middle Eastern, but also Tokharian), and last of all Turko-Mongol. The dates square with the hypothesized origin of cavalry warfare north of the Black Sea ca. 700 BC, followed by its spread E and W reaching China around 300 BC.

Racially, as far as I know steppe and C. Asian peoples have always included mixed Caucasian / E. Asian traits, with different mixes. The Turks are a good example of a linguistically-defined people with very little racial identity at all, ranging from probably 80-90% E. Asian in the east to 80-90% Middle Eastern (probably with a significant W. European component) in Turkey.

I can recommend: Keightley, David, ed., The Origins of Chinese Civilization, California, 1983.

Most of what's on the internet about the genetics of the Turks of Turkey is amazing nationalistic garbage. Wiki says:

"While most historians believe that the actual migration of Turks was relatively small, a genetic testing carried out on a small sample revealed that as much as 30% of Turks have varying degrees of Central Asian ancestry. Although, result of another genetic testing carried out on a much larger sample suggests that the actual Central Asian ancestry could be less than 9%."

Wiki isn't reliable either, of course, though that's in the ballpark, I think. The Turks of Central Asia have a big E. Asian component.

For a specialist in Chinese history there may not be very much "new" here. For a broader audience like me, who has really studied history on a broader scale, EVERYTHING is new here.

I see no reason, why to downplay the fascination of discovering a culture and a cultural region and a phase of world history, that was no one aware of outside the circles of the specialist's.

A lot of science is undone because of shortage of communication (or exchange of fascination) between scholars of very different discipline's and because of shortage of communication of knowledge to a broader audience.

Look what geneticist Frederika Kaestle is asking in "National Geographic". If you know a LITTLE BIT about "Sogdian history", you say: Very dumb questions! At least: Not very precise questions. (Questions without "background-knowledge".) - But who has known yet anything about - - - "Sogdian history"???

It seems, that for a long time, this knowledge was not very welcome in China. And because in China we have the richest sources about the history of "this region" and about the Sogdians, we become aware now of "all that", because Chinese scholars are free now, to become aware more and more of - "all that".

I think, you can see a paradox here: In Chinese art of the Tang-area Sogdians are most clearly shown as Caucasians. But if you look at the art in Samarkand and in the Tarim at that time, you can find Caucasian features (for example blonde hair and so on) between a lot of "Middle Eastern type"-features also. What is the explanation for that? Were they mixed? Surley.

But may be there is another explanation also: "Style". If you have "buddhist art", people are mostly not shown "100 % Caucasian", they mostly look "Middle Eastern". And also Assyrian art and so on.

But what's the matter now with (non-buddhist, non-manichaen ...) "original" Chinese art of the Tang area? Chinese people are shown as 100 % "East Asian". And Sogdians are shown as - - - 100 % Caucasian. - Style? May be. May be something like "pronouncing differences"? Or is this a preference of Chinese psychology for 100 % Caucasian features? We have some incidences for that (ask an East Asian of today ...).

Mostly Sogdians in Chinese art are shown as very sympathetic people, as comedians and so on. It seems: Everyone loved them. Everyone was delighted about them, everyone was amused. In those times, it seems, they were very welcome in Tang-China. - Any parallels to today???

We speek about "ionische Heiterkeit" (greek serenity). Has there exist something like a "Sogdian/Tang chinese serenity"???

If you look at modern day Asian art such as Pokemon you also see round eyes. Founders effect?

"Or is this a preference of Chinese psychology for 100 % Caucasian features? We have some incidences for that (ask an East Asian of today ...)."

If the remarks that I hear on a frequent basis about long noses, heavy brows, and sunken eye sockets are any indication, I suspect that this is unlikely.