Sunday, April 30, 2006

Finnetics   posted by Razib @ 4/30/2006 11:56:00 PM

Via Dienekes I found this important new paper on Finnish genetics, Regional differences among the Finns: A Y-chromosomal perspective. This is a meaty paper, so I put it up in the GNXP forum files ("finnY"). Here is the abstract:

Twenty-two Y-chromosomal markers, consisting of fourteen biallelic markers...eight STRs...were analyzed in 536 unrelated Finnish males from eastern and western subpopulations of Finland...These results suggest that the western and eastern parts of the country have been subject to partly different population histories, which is also supported by earlier archaeological, historical and genetic data. It seems probable that early migrations from Finno-Ugric sources affected the whole country, whereas subsequent migrations from Scandinavia had an impact mainly on the western parts of the country. The contacts between Finland and neighboring Finno-Ugric, Scandinavian and Baltic regions are evident. However, there is no support for recent migrations from Siberia and Central Europe.

Points of note.

1) mtDNA and Y lineages often give different results. As the paper emphasizes this may be because of different population histories (e.g., Mestizos tend to exhibit Western European Y chromsomal profiles and Amerindian mtDNA because of their ethnogenesis), or, it may be because of sociological dynamics (patrilocality tends homogenize mtDNA distributions while fostering local Y substructure). Other factors like selective sweeps on mtDNA could also result in a difference.

2) There is a east to west gradient in markers. This shouldn't surprise too much. About 10% of the variation was accounted for by this population vs. population difference (80% was intragroup, while 10% was between groups within the subpopulation).

3) I've noted before that R1b, which is modal in much of western Europe, is rather rare in Finland (and is found in moderate frequencies in Sweden). Also, M17, which is associated with Slavs in a European context, is also found at moderate levels in Finland (M17 in England seems to be associated with settlement in the Danelaw by Norwegians and Danes).

4) I am a bit confused as to whether these data included Finns of Swedish ethnicity.

5) The authors note that they do detect the signature of migrations to areas where there is recent attested resettlement by Finns from a particular locale.

6) The authors reiterate findings that the Finnish Y lineages show no evidence of some found at high frequencies in Siberian groups which also carry the common Finno-Ugric Tat C marker. In other words, we can probably eliminate the possibility of a recent admixture event with a Siberian group to explain the peculiarities of the Finnish Y chromosomal profile (either the Siberians received Tat C from Finland, or, I think more likely there are particular similarities amongst the circumpolar peoples of Eurasia which have a deep time depth before their later diversification and admixture).

7) The nonrecombinant portion of the Y chromosome has a lot more sequence to analyze than the mtDNA. This gives researchers more information to work with, but, my understanding is that the molecular clock is far less precisely calibrated than on the mtDNA, so the time frame tends to be sketchier.

Overall, this paper reinforces the idea that Finns are distinct from the peoples of Western Europe, seeing as they have little evidence of R1b, but that they share considerable continuity with other Scandinavians, as well as peoples to the East (Slavs). One issue that I think needs to be addressed is that the mental model people have in regards to the genesis of the Finns is often of a group of Siberian tribes hurtling through "Slav space" and settling amongst a bunch of Scandinavians and slowly admixing. I think it is easy for people to imagine "clumps" of populations in a larger distinct matrix, and then model the mixture of clumps resulting in the peoples we see around us. I suspect that the reality is that many of the genetic gradients are the result of more prosaic deme-to-deme mate exchange and movement over time. Large migrations might have played a role, but the introgression of M17 into Finland (if it wasn't indigenous to Finland in the first place) need not be explained by a few movements of Slavic tribes, rather, it might have been due to the long term residence of Slavs along the southern edge of the Finnish world and the inevitable bleeding over of marriage networks.

In any case, the paper has a lot of historical context and conjecture, and I'm curious what some of the Finnish readers think about those points.