Tuesday, November 20, 2012
Scythian mtDNA from Iron Age Russia
I already blogged about these and other ancient Russian samples very briefly a few weeks ago after reading the Oleg Balanovsky thesis (see here). However, what I didn't realize at the time was that a more extensive description of the samples was included in a 2011 thesis by someone called Clio Der Sarkissian. So here we go again...
Based on informative haplotype matches, the Rostov Scythians show clear affinity to modern European samples, especially those from Eastern Europe, including Poles and Russians. However, as mentioned in my previous blog entry, the Scythian mtDNA is much more exotic than that of most modern Eastern European populations, carrying heavy influence from North and East Eurasia, and some minor input from the Near East. Hence, on the PCA plot this ancient Rostov sample pulls away from the mainstream Eastern European cluster, and lands close to groups that also carry various exotic admixtures, like Tatars (TA2), Shugnans from Tajikistan (shu), Udmurts (UD), Komis (KO), and Pomors from Northern Russia (pom).
We'll need more Scythian aDNA, including Y-chromosomes and autosomal DNA from different periods and locations, to learn precisely how these groups acquired their eastern admixture. However, we already know from archeology and historical texts that Scythians were highly mobile and came into contact with a myriad of groups from across Eurasia, so their mtDNA should reflect that.
In any case, looking at the PCA plots above, it seems unlikely that the Rostov Scythians originated in West Asia or South Central Asia. These and other areas have been proposed, at one time or another, as alternatives to the more widely accepted theory of an Eastern European homeland for the proto-Scythians. But note the distances between the Scythian sample and modern Ossetians (SE-N and SE-S), Georgians (GEO), Armenians (ARM), Kurds (kur) and Iranians (IRN) on the PCAs above. These are remarkably large considering the geographic location of Rostov-on-Don (ie. not too far away from the Caucasus).
Note also the unusually western position of the Indo-Iranian Shugnans from Tajikistan on the PCA plots. They're very close to the main European cluster, and this is due to their relatively high frequencies of West Eurasian mtDNA haplogroups, especially mtDNA H (29.4%). Isolation in the Pamir mountains and subsequent genetic drift probably has a lot to do with this outcome, but I suspect there's more to the story. That's because back in 2008 we learned that two Shugnan individuals matched an ancient mtDNA K1b haplotytpe from Corded Ware remains from a site in eastern Germany (see here). Thus, the Shugnans might be in-part direct descendants of Europeans who migrated all the way to the Pamirs sometime during the metal ages.
This thesis is something of an epic, and unfortunately I don't have time at the moment to do it justice with one blog entry, so please check it out for yourselves, since it's publicly available. However, it's also worth mentioning that Der Sarkissian is yet another scholar who's noticed that the major portion of modern Eastern European genetic diversity seems to have come from somewhere in the west, like Central Europe.
She suggests that the west to east movements of the Indo-European Slavs and Germanics were responsible for this shift in the character of Eastern European DNA, from significantly East Eurasian-like to basically West/Central European. I think anyone with at least a reasonable grasp of population genetics has to agree with this sentiment based on latest DNA results from modern and ancient Europeans, and it's something I've talked about regularly on these blogs. Indeed, I'd say that the people who were to become the Scythians on the Russo-Kazkah steppe were also part of this long running tradition of eastward movements across Europe, except that they moved deep into Asia, and then back to Eastern Europe again.
Clio Der Sarkissian, Mitochondrial DNA in ancient human populations of Europe, Thesis, 2011, The University of Adelaide, South Australia, School of Earth and Environmental Sciences
Post-Mesolithic population replacements/extinctions in Northeastern Europe
Ancient Siberians carrying R1a1 had light eyes - take 2
The history of slavs in the light of Y chromosome and mtDNA variability
Russian mtDNA, Goths of the Ukrainian steppe, and a proto-Slavic expansion from present-day Poland (Morozova et al. 2011)