Saturday, 14 May 2011

Inland Ocean. Restricted Pole Run: Part III

This is the third part of the restricted pole run of Western Eurasia. All results are from the same set-up and analysis. This part concerns Central Asian and Siberian populations. Central Asia is a sparsely populated Steppe expanse connecting all major Eurasian population centres: West Eurasia, East Eurasia, and South Eurasia, and these with remaining Siberian populations to the North (today mostly replaced by Russians).
Like finding ancient bones is tropical areas, finding ancient population genetic fossils in Steppe populations is probably more difficult. Unlike settled agriculturalist populations, who I think present much more continuity since the Neolithic Revolutions, there have likely been major changes in the sparsely populated, pastoralist inhabited, sand and grass oceans of the Eurasian interior.
For instance historically it can be presumed that such populations were more "West Eurasian" thousands of years ago than they are now, since a North or East Asian component has become important or even predominant. Still, looking at the Fertile Crescent-related components across the populations, we can perhaps get hints about early Western Neolithic influence. Component proportions preserved across all groups likely were derived from founding populations. Those exhibiting clines, maybe more likely introduced more recently.

For more extended interpretations of the components please read my previous two posts.
In retrospect, I think using the "Chuvash5" as the NMPC pole may have underestimated it and overestimated a bit the "Basque5" one. Next time I may use a combination of Chuvash and Lithuanians and see what happens.

Regarding the above results, some considerations:
1) Uzbekistan Jews seem to have, like most Jewish populations, a predominant Levantine element. They give better contrast to patterns consistent between the other Central Asian populations.
2) All Central Asian populations have large Yakut and Mongolian-like components corresponding to a likely Turkic and Mongolic element.
3) All Central Asian populations also have a "Fertile-Crescent" element composed of EMPC+NMPC+2nd Wave in that order of importance. This element is quite similar to that of the Caucasus populations. These last don't have much Turkic/Mongolic. A good model explaining these patterns is that the Central Asia steppe (as opposed to the river valleys of the Ukraine and South Russia) was initially populated by a Fertile Crescent element coming from the Caucasus/Iranian plateau at a relatively later date.
4) The Turkic/Mongolic component varies widely in a cline between them. Removing it, allows for a much better view of Fertile Crescent element patterns:
CAsia is a participant, mostly Kazakh in origin I believe. Hazara may have more EMPC due to admixture with Iranian plateau populations. PonticCaspian, a participant represented in the main graph above, with Moldavian Gagauz and some Ossetian ancestry presents much the same pattern except with higher WMPC (possibly due to proximity to Balkan/West Caucasus populations). Much of the same pattern can be observed in Altaians and Buryats, in a much smaller FC element.
I really don't see population changes after the initial invention/introduction of advanced pastoralism producing such an homogeneous pattern (bear in mind some of these are small components, indeed all of these in the Mongolian case are small, since they're mostly an Eastern population and can be overinflated by the exclusion of major "Siberian" ancestry). Certainly not from Mongolia to the far west. These patterns I think most likely roughly correspond to the original Kurgan pastoralist people, and possibly also to the ancient Tocharian peoples.
5) Northeast Europeans have much NMPC but little EMPC. This "Chuvash5" element could have come from the same region at an earlier time, before or in the beginning of the EMPC expansion/ intrusion. Some small EMPC elements in Northeast European populations may indicate that the expansion Northwards into more marginal lands of NMPC was driven by competition/conflicts with the EMPC intruders.
6) Another explanation for EMPC in Northeast Europeans is a secondary expansion of Steppe peoples into the region, after the NMPC primary expansion.
- WMPC+NMPC in Koryaks, Chukchis and other Siberians should correspond to recent Russian admixture. WMPC may be overestimated in this run, but proportions appear similar in Russians in my previous post.
7) Caucasus mountain valley populations appear to have preserved various demographic "pictures" of past admixture patterns (much like Basques and Sardinians), pointing to demographic changes in the Caucasus-North Fertile Crescent region: firstly mostly NMPC agriculturalists expanding into the rivers of the Ukraine and South Russia, as seen in Lithuanians (and Chuvash); then affected by the EMPC expansion as seen in the Urkarah; later affected by the "2nd wave" (WMPC+NC) as seen in Lezgins and Stalskoe. It seems it was at this last stage that pastoralist populations emerged into the steppes, otherwise it is difficult to explain the remarkable consistency in EMPC vs NMPC proportions in all pastoralist populations sampled.

So the current model I think most likely:
-NMPC was primarily an early (pre-EMPC expansion or simultaneous to it) agriculturalist expansion into the river valleys of South Russia and the Ukraine, likely not affecting the remaining marginal steppe to a large extent.
-Populations from the Caucasus and Iranian plateau were then heavily affected first by the EMPC and then to a smaller extent by the subsequent 2nd wave (WMPC+NC) secondary expansions. These had "higher drag" and didn't affect more northern NMPC populations much (possibly also due to much colder climate rendering secondary wave innovations less applicable).
-At some point not long after the WMPC+Nile Core expansion (so around 3000BC or so), people from the Caucasus and/or Iranian plateau expand into the Steppe with developed pastoralist lifestyles, probably identifiable archaeologically with the Kurgan culture.
-All these steppe populations are subsequently affected, in a more clinal thus more recent way, by Siberian/East Asian elements, corresponding to Turkic/Mongolic expansions.

I thought this would be the last post from this run, but I've decided to leave some South Asian and other individuals I included in the run (just a few samples, results without them aren't appreciably different) for later, since otherwise it's too much for just one post. I'll present the spreadsheet and individual participants then, possibly today if I can find the time.

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