суббота, 11 мая 2019 г.

Uralic-specific genome-wide ancestry did make a signifcant impact in the East Baltic

I’ve started analyzing the ancient genotype data from the recent Saag et al. paper on the expansion of Uralic languages and associated spread of Siberian ancestry into the East Baltic region. The paper is freely available here and the data here.
I really like the paper, but I don’t agree with the authors’ claim that the appearance of Y-chromosome haplogroup N in what is now Estonia and surrounds during the Iron Age is «not matched by a clear shift in autosomal profiles». In my opinion it certainly is, and, as one would expect, it’s a shift towards a genetic profile associated with western Uralic speakers.
I’d say that the easiest way to find this signal is with a Principal Component Analysis (PCA) focusing on fine scale genetic substructures within Northern Europe, like the one below. The relevant datasheet is available here.

Note that the East Baltic Iron Age samples, all from burial sites in what is now Estonia, appear to be peeling away from their Bronze Age predecessors and overlapping strongly with present-day Estonians, who are Uralic speakers. Indeed, the PCA suggests to me that the formation of the greater part of the present-day Estonian gene pool took place in the East Baltic during the transition from the Bronze Age to the Iron Age. In other words, when Uralic languages are generally accepted to have arrived in the region from near the Ural Mountains in the east.
I was also able to closely replicate these outcomes with my Global25 data using the method described here. However, in this effort, present-day Estonians are, overall, shifted slightly west relative to the Estonian Iron Age samples (EST_IA), which might be due to the presence of low level Germanic ancestry in Estonia dating to the medieval period. The relevant datasheet is available here.

Interestingly, the Estonian Bronze Age samples (EST_BA) come from stone-cist graves which are widely hypothesized to have been introduced to the East Baltic from the Nordic Bronze Age civilization. I even recall reading a paper on the topic which claimed that the remains buried in such stone-cist graves were those of Proto-Germanic-speaking Scandinavian migrants. Well, I haven’t had a chance to study these samples in any great detail yet, but considering that in both of the PCA above they’re overlapping strongly with Latvian Bronze Age samples (LVA_BA) and sitting far away from the nearest Scandinavians, I’d say they’re probably of local stock from way back.
See also…
It was always going to be this way
On the association between Uralic expansions and Y-haplogroup N
Inferring the linguistic affinity of long dead and non-literate peoples: a multidisciplinary approach


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