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Wednesday, September 14, 2011

Sharp genetic discontinuity between Eastern Europe and the Caucasus


The rather artistic PCA below shows genetic clines that run through West Eurasia. It basically suggests that Europe and the Caucasus were populated by similar populations from the Near East, but didn't mix much after that. There appears to be some Russian influence among a few samples from the Caucasus, but no significant admixture from the Caucasus in Ukraine or Russia.




The Caucasus, inhabited by modern humans since the Early Upper Paleolithic and known for its linguistic diversity, is considered to be important for understanding human dispersals and genetic diversity in Eurasia. We report a synthesis of autosomal, Y chromosome and mitochondrial DNA (mtDNA) variation in populations from all major subregions and linguistic phyla of the area. Autosomal genome variation in the Caucasus reveals significant genetic uniformity among its ethnically and linguistically diverse populations, and is consistent with predominantly Near/Middle Eastern origin of the Caucasians, with minor external impacts. In contrast to autosomal and mtDNA variation, signals of regional Y chromosome founder effects distinguish the eastern from western North Caucasians. Genetic discontinuity between the North Caucasus and the East European Plain contrasts with continuity through Anatolia and the Balkans, suggesting major routes of ancient gene flows and admixture.

Bayazit Yunusbayev et al., The Caucasus as an asymmetric semipermeable barrier to ancient human migrations, Mol Biol Evol (2011) doi: 10.1093/molbev/msr221 First published online: September 13, 2011

4 comments:

Onur said...

I have been corresponding via email with Mait Metspalu, one the authors of both this paper and the Behar et al. 2010 paper, for some months. In our correspondence Mr. Metspalu informed me that all of the Turkish samples used in this paper are exactly the same samples as all the Turkish samples used in Behar et al. 2010 (19 in total) and, more importantly, that all of the Behar et al. Turks (consequently also all of this paper's Turks) were sampled from the region of Turkey that is historically known as Cappadocia. This confirmed my suspicions, as ever since the publication of the Behar et al. 2010 paper I had been suspecting that the Turks used in Behar et al. 2010 were from a rather limited region of Turkey, and their contrast with the genetically much more heterogeneous Dodecad Turks, who are from all over Turkey, had increased my suspicions. Now my suspicions are confirmed by Mr. Metspalu. So, as Dodecad Turks are from all over Turkey while all the Turks used in this paper and the Behar et al. 2010 paper are exclusively from the historic Cappadocia region, the Dodecad Turks are much more representative of the ethnic Turkish genetic variation than the Turks used in this paper and the Behar et al. 2010 paper.

According to the Dodecad Project's standard ADMIXTURE analysis results, the most noticeable differences between the Dodecad Turks and this paper's/Behar et al 2010's Turks are that the average of the sum of the Mongoloid component percentages is 5.2% for the Dodecad Turks (as of now 23 samples in total) and 6.9% for this paper's/Behar et al 2010's Turks (as I said, 19 samples in total), that the average of the South Asian component percentage is 2.3% for the Dodecad Turks (less than that of the Dodecad Armenians [20 samples in total as of now], which is 2.8%, and almost equal to that of the Dodecad Assyrians [12 samples in total as of now], which is 2.2%) and 3% for this paper's/Behar et al 2010's Turks, and that on average the Dodecad Turks have more West European, more Mediterranean, more Southwest Asian and less West Asian component percentages than this paper's/Behar et al 2010's Turks. Also according to the Dodecad Project's standard ADMIXTURE analysis results, the average of the sum of the Mongoloid component percentages of the Dodecad Turks (5.2.%) is very similar to the average of the sum of the Mongoloid component percentages of the HGDP Adyghe (5.5%), for whom Mr. Metspalu informed me that they are at the same time the Adyghe samples used in this paper and the Behar et al. 2010 paper by the way.

Davidski said...

Do you know if the raw data from this paper is going to be available at GEO?

Onur said...

Hi David,

I've contacted Mr. Metspalu in response to your question, and he has informed me that the raw data from this paper will indeed be available in GEO format but also that it will take some for that. He has also stated that the raw data will be available on his website in bed format too. He has invited you to directly contact him on this matter; his email address can be found on the web.

Onur said...

BTW, Mr. Metspalu also told me that all of the Behar/Yunusbayev Turks are from the autocthonous Turks of the historic Cappadocia region, so, for instance, they do not descend from the emigrants from the Balkans or the Caucasus to that region. So the Behar/Yunusbayev Turks can at most represent Turks from the historic Cappadocia region. I say at most, as Mr. Metspalu doesn't know from which provinces of the historic Cappadocia region they are, he only knows that they are all from the historic Cappadocia region and all autocthonous Turks of that region. So they may be from a single province of the historic Cappadocia region or from multiple provinces of it, only the sample collectors know these details according to Mr. Metspalu.