Tuesday, December 15, 2015

Dagestani Genetics

Dagestan, in the Caucasus Mountains, has many linguistic groups and ethnicities.  A recent study examined the population genetics of the modern inhabitants of Dagestan.  Genetic differences more closely track linguistic differences than geography.

Y-DNA distinctions were particularly great with Y-DNA haplogroups J1-M267*, R1b-L23, G2a-U1, and R1a-Z93 appearing particularly prominent in some subpopulations.  The first two of most distinctive of the Nakh language speaking people, with the contributions of the other two being relatively minor and the percentages of J1-M267* being greater than that of R1b-L23.  In PCA analysis, Dagestani Y-DNA shows a cline from Europe to Central and South Asia to the Near East to Dagistan.

The mtDNA mix was more uniform across the region crossing linguistic boundaries, suggesting a history of bride exchange with geographically nearby groups. In PCA analysis, Europe's mtDNA looks like a subset of much more diverse Dagestani mtDNA, there is modest overlap with Near Eastern mtDNA, and the mtDNA of Central and South Asia overlaps modestly with the Near East, but not at all with that of Dagestan which encompasses all of the mtDNA diversity of Europe and more.

There were also significant autosomal genetic distinctions between the subpopulations and a Tree-Mix analysis showed little evidence of meaningful admixture between the subpopulations.  In a PCA analysis, Dagestani autosomal genetics are surrounded by a ring of geographically nearby populations - clockwise, Central and South Asians, Near Easterners, Europeans, and other Caucasian (a group in turn adjacent to Central and South Asians).

Mutation based efforts to identify the age of the populations based upon their genetic diversity suggest that the Nakh language speaking people of Dagestan are descendants of the original Neolithic farmers of the region and date to about 6000-6650 years ago, an estimate consistent with the estimate based upon linguistic analysis of differences between languages in that language family.


terryt said...

"The mtDNA mix was more uniform across the region crossing linguistic boundaries, suggesting a history of bride exchange with geographically nearby groups".

I'm not so sure that is the explanation. To me it is more likely that the Y-DNA has spread across pre-existing mt-DNA haplogroup distribution. Especially likely to be so as the 'mtDNA mix was more uniform across the region'. One would expect at least some regional differences if the distribution was a product of bride exchange. And in general we find the mt-DNA in any particular region is older than the Y-DNA. To me the same explanation stands.

andrew said...

Good point. This suggests then, that the mtDNA distribution is pre-Neolithic or at best first wave Neolithic. It also makes the current mtDNA distribution in Europe look like a serial founder effect from this larger Caucasus base.

terryt said...

I think that is probably correct.