May 25, 2004
Y chromosome Haplogroup I
I will write some more when I finish reading this study...
Am. J. Hum. Genet., 75:000, 2004
Phylogeography of Y-Chromosome Haplogroup I Reveals Distinct Domains of Prehistoric Gene Flow in Europe
Siiri Rootsi
To investigate which aspects of contemporary human Y-chromosome variation in Europe are characteristic of primary colonization, late-glacial expansions from refuge areas, Neolithic dispersals, or more recent events of gene flow, we have analyzed, in detail, haplogroup I (Hg I), the only major clade of the Y phylogeny that is widespread over Europe but virtually absent elsewhere. The analysis of 1,104 Hg I Y chromosomes, which were identified in the survey of 7,574 males from 60 population samples, revealed several subclades with distinct geographic distributions. Subclade I1a accounts for most of Hg I in Scandinavia, with a rapidly decreasing frequency toward both the East European Plain and the Atlantic fringe, but microsatellite diversity reveals that France could be the source region of the early spread of both I1a and the less common I1c. Also, I1b*, which extends from the eastern Adriatic to eastern Europe and declines noticeably toward the southern Balkans and abruptly toward the periphery of northern Italy, probably diffused after the Last Glacial Maximum from a homeland in eastern Europe or the Balkans. In contrast, I1b2 most likely arose in southern France/Iberia. Similarly to the other subclades, it underwent a postglacial expansion and marked the human colonization of Sardinia 9,000 years ago.
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In conclusion, although haplogroup I represents only a single piece in the puzzle of European genetic variation, its essential continental specificity and the clearly defined phylogeographic patterns of its subclades contribute uniquely to understanding the human settlement of Europe. Haplogroup I provides an exceptional record of European-specific paternal heritage, including pre-LGM differentiation followed by contraction, isolation, and subsequent post-LGM expansions and spread. Still, the wide CIs in the time estimates dictate caution in definitively linking the phylogeography of this haplogroup with known prehistoric and historic scenarios. Nonetheless, the I1a data in Scandinavia are consistent with a post-LGM recolonization of northwestern Europe from Franco-Cantabria, whereas the expansion of I1b* in the east AdriaticNorth Pontic continuum probably reflects demographic processes that began in a refuge area located in that region.
Posted by Dienekes at May 25, 2004 08:12 PM | PermaLinkI don't think it's yet known what is the frequency of my haplogroup, I1b, in Greece. In one of the Y DNA studies, I forget which one (Di Giacomo et al.?), Haplogroup I was found to be not infrequent in Greece--even in remote Crete. But what branches of this Haplogroup were found in Greece? I don't remember the Y DNA tree, but don't many branches emanate from I-M170? There seemingly can't be much I1a or I1c in Greece, given the distance of their origins.
It would seem to me that the part of I that originated in the Balkans would be more prevalent in Greece than the other branches, and it wouldn't surprise me that the I1b branch would have been present to some degree in ancient Greece, given the proximity of its origin.
The frequency of Haplogroup I in the Balkans proves that invasions of thousands and possibly tens of thousands of years did not alter the indigenous populations.
According to this study, Greeks have 13.8% I in total which is: 1.5% I*, 2.3% I1a*, 8.4% I1b*P37, and 1.5% I1c.
Posted by: Dienekes at May 27, 2004 11:44 PMIt would be interesting to do genetic studies on certain Greek population groups, namely the Tsakonians and the Maniates of southern Greece. I think there's a mountain ridge or line of mountains running north-south that separates the dwindling Tsakonian speakers from other Arcadians. I wonder if these people are genetic isolates or are similar to their neighbors.
The Maniates are an interesting group in that they are reputed to be descendants of ancient Spartans and have a history of isolationism and belligerence, possibly providing genetic isolation. An aquaintance of mine from Mani said that no Turkish foot was set there--of course this may be an exaggeration, but what is meant is that Turks never established a foothold there. She said Maniate women fought Turks with "drepania" (sickles?).
Time is of essence in the study of the Greek rural population because I've read that many Maniates moved out of Mani--some went to Athens--and Greece is becoming populated with other races. My mom, who goes to Greece almost every year, said her village has Russians, Albanians and others, whereas before it only had Greeks.
It seems that Greek genetic studies focus on urban areas, which probably contain Greeks from all over Greece.
Posted by: Dean at May 28, 2004 08:36 PM