Why the Uyghurs as we didn’t know them didn’t exist until after 1000 AD

The period between 300 AD about 750 AD is sometimes termed the “Buddhist Age.” The reason for this is is that this was the period when Buddhism was established in China, and, was still a force in mainland South Asia. It is also when Buddhism was arguably the dominant religion in much of Central Asia. In fact, Buddhism probably arrived in China mostly through this route, via the city-states of the Tarim basin.

A point of interest for many in the public is that some of these Tarim basin Buddhists looked very “Western.” That is, they had European features and coloring. The reason for this is that their ancestors were the eastern edge of the Indo-European migrations on the steppe. Many of them famously spoke Tocharian languages, an extinct branch of the Indo-European languages. But others spoke Iranian languages. Iranian not in that they came from Iran, but that they were descended from proto-Iranians of the steppe.

A few years ago there was a discussion on this weblog and elsewhere about very recent admixture dates for the western and eastern admixture components in the Uyghurs. That is, after 1000 AD. This struck many as too recent. I think perhaps I have an answer for what happened.


The admixture plot to the right has Uyghurs with some ancient and modern samples. The Uyghurs are about 50% East Asian, as you’d expect. But the balance of their ancestry is split between Indo-European populations, and those of Neolithic Iran (with a slight bias toward the former).

Were the Indo-Europeans who arrived in the Tarim basin 4,000 years ago different from their cousins to the west? I doubt it. Rather, the “Iranian” ancestry came later. And I think I know how it came: the modern Uyghur language is actually descended from a dialect of Karluk Turk. It is not related to the ancient Uyghur language. After 1000 AD the process of Islamicization that occurred in the Tarmin basin expanded from the western edge, in Kashgar, until the final Buddhist Uyghur kingdom of Turfan in the east fell.

A simple model of elite diffusion suggests Islamicization and language-shift occurred without demographic perturbation. But another alternative is that the switch to Islam and the Salar language resulted in gene flow from Central Asia proper, into the Tarim basin. The people of Central Asia were Turkicizing at this period, but their origin was as Iranians. Many of these people were an admixture of people from the Pontic steppe, and, the Iranian agriculturalists.

If in the future someone does a temporal transect of the Tarim basin, I predict that one thing they will note is the sharp rise in Iranian agriculturalist ancestry over time, with a particular jump around 1000 AD (though the Sogdians were also a presence in these city-states).

12 thoughts on “Why the Uyghurs as we didn’t know them didn’t exist until after 1000 AD

  1. I am not sure this makes sense.

    Even Buddhism came into the Tarim Basin from the West and Southwest, from regions rich in Iran_N ancestry. So why should one wait for the western genetic influx until the Islamic period ?

    Further, Iranian Neolithic ancestry was widespread all across Central Asia and even on the steppe already around 4000 BC. So why should Iran_N ancestry have come into the Tarim Basin much later ?

  2. Might be worth putting some Central Asian Eneolithic / Copper Age proxies in rather then the neolithic Iran which are Western Iran.

    Not sure one way or t’other about Uyghur ethnogenesis model, only thing I would note is probably worth comparing to Damgaard’s “137 ancient human genomes from across the Eurasian steppes” – https://www.nature.com/articles/s41586-018-0094-2?

    My impression is using those samples the Eurogenes data, the Tian Shan groups from west end of north of Tian Shan Inner Asian Mountain Corridor (Saka / Hun / “Iron Age Nomad” / Wusun) from at least 500 BCE seem to show an admixture cline from Bronze Age Mongolia to Central Asia (Turkmenistan Iron Age, Haji Firuz Iron Age, etc) and in present day closest to Tajiks.
    Uyghurs look on a cline with a still more southern end point than this, but Iron Age samples are not terminating in pops like Sintashta, or even more Iran_N influenced Sarmatians and Scythians. Kazakhstan_Karluk sample from 1000 AD is basically the same as Uyghurs in composition.

    But I don’t know what that does or does not tell us about Tarim.
    (Extremely messy looking PCA using Eurogenes data: https://imgur.com/a/vTnZOES)

  3. I am thouroughly confused:

    “Iranian not in that they came from Iran, but that they were descended from proto-Iranians of the steppe.”

    “Many of these people were an admixture of people from the Pontic steppe, and, the Iranian agriculturalists.”

    Are the people from the Pontic step, the proto-Iranians? and are the Iranian agriculturalists related to the proto-iranians?

  4. Even Buddhism came into the Tarim Basin from the West and Southwest, from regions rich in Iran_N ancestry. So why should one wait for the western genetic influx until the Islamic period ?

    buddhism was not associated with a language shift. so it is probably more like buddhism coming into china. islam came with a language shift.

  5. Are the people from the Pontic step, the proto-Iranians? and are the Iranian agriculturalists related to the proto-iranians?

    the iranian languages are from the pontic steppe. scytihans and sarmatians spoke iranian language, but were never in iran.

  6. And the second question? Are the Iranian Agriculturalists, Persians?

    I believe that in discussions of Indian ancestry you talked about Iranian agriculturalists, but from context, I thought you were referring to pre-Indo-European inhabitants of the area that is modern Iran.

  7. like in south asia, most of the ancestry in iran, is not from indo-iranians. it is from ‘iranian agriculturalists’, who date to the early holocene, and began to expand out of the zagros. the ‘indo-iranian’ ancestry seems to increase the further north and east you are in iran as well, so the fars, where the persians emerged from (home two major dynasties), is almong the less ‘iranian’ in the sense of total ancestry derived from the steppe.

  8. That’s pretty close to when Genghis Khan (and sons) conquered everything from Turkey to China, which seems like a pretty reasonable time for a major shift in population genetics.

  9. Modern Uighurs did come from further west. Even their relationship with medieval Uighurs is in doubt. Some think present day “Uighurs” are a modern invention.

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