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Friday, November 14, 2008

Y chromosomes of Sicily


In May of 2008, Cornelia Di Gaetano et al submitted an article to the European Journal of Human Genetics studying the Y chromosome makeup of the island of Sicily. Sicily has one of the highest frequencies of Haplogroup J2 (M172) in the mediterranean. J2-M172 made up 33% of the Y chromosome signatures on the island and was non-randomly distributed occurring at higher frequencies in the eastern areas of the island. This distinction was evident in the subclades, M67 and M92, which have previously been linked to Greek and proto-greek colonization. Both M67 and M92 were twice as frequent on the eastern portion of Sicily which displays more archaelogical traces from the Greek classic era. Even the paragroup of undistinguished J2 haplotypes (M172) was more than twice as frequent in Eastern Sicily. One of the more interesting subclades, referred to as J2a1k (DYS445=6) showed an interesting non-random distribution in Sicily. This subclade is also commonly referred to as J2a1h (ISOGG) or J2a-Lambda (J2 DNA Project). Most striking was differences in frequencies between Mazara Del Vallo and Sciacca. Mazara Del Vallo is a port city established by the Phoenicians in the 9th century B.C. while Sciacca, known as Thermae in Greek times, was founded in the 5th century B. C. by the Greeks. These 2 cities, founded by different groups are only 57 KM apart. Yet 11.11% of the Y chromosomes in Mazara del Vallo were J2 M172 with DYS 445=6 while this subclade was absent from the sample data from Sciacca. Trapani, another port city in Western Sicily also exhibited high levels of J2-M172 with DYS 445=6 at 9.09%. This subclade was absent from the inland cities of Santa Ninfa and Piazza Armerina and the northern Sicily town of Caccamo. The data seems to suggest that J2a1h (J2a1k)'s distribution is stronger in coastal regions of Western Sicily and more rare in inland and Eastern parts of the island. The sole exception to this trend was the data from Troina which did report 10% J2 M172 with DYS 445=6. Overall the non-random and high levels of J2 on the island of Sicily seem to reflect the complex history of the island and might represent multiple migrations by multiple groups over various periods of the islands history.

The general heterogeneous composition of Hgs seen in our Sicilian data is consistent with similar patterns observed in other major islands of the Mediterranean, like Sardinia and Crete, possibly reflecting the complex histories of settlements in these islands during the Holocene.

(Link)

3 comments:

Al Aburto said...

Very nice read and paper. Thank you M172! I think though that the discussion of J2a1h was not very affirmative. I mean, how does one deduce that J2a1h arrived with the "first farmers"? Also, why was the Phoenician aspect not connected to J2a1h when it seemed somewhat obvious from the discussions? Regardless, a thought provoking blog post and article.

m172 said...

yes, the paper seems to have lost direction with respect to Western Sicily and there is no solid theory provided with respect to J2a1h in the paper.

BES said...

Thanks, great posting, David! But no fair calling J2a1* (which my paternal line belongs to) "undistinguished"! ;-) . . . I know you meant "undifferentiated.". . It's a paragroup rather than a clade; it's paraphyletic (http://en.wikipedia.org/wiki/Paraphyletic), to throw around a couple more technical terms.

The findings on Sicily, which you've described so clearly, largely agree with what Whit Athey and I estimated using a Bayesian analysis of YHRD data from these same towns in Sicily. The only difference was that we did find some J2a1h in Piazza Armerina, and a higher rate in Eastern Sicily than Western, when Troina, Piazza Armerina and Ragusa were pooled for the East, and the rest pooled for the West, but of course we didn't have access to actual DYS445 data. We did see the strong contrast between Mazara and Sciacca. Sicily is a complex mosaic, and the East-West division isn't always the most meaningful one.

Another pattern they haven't explored at all is the distinction between the J2a1h who have 10 at DYS391, and those with 9. There are numerous other marker values that distinguish the haplotypes with 391=9, which so far have been found to be more common and widely distributed, from the others, which have a more limited distribution. In the sampling by Di Gaetano et al, the group with 391=9 is found in four locations in all corners of the island, while J2a1h with 391=10 is found only in Trapani (where it was the only kind) and Troina. Those two towns are both in the North of the island, though we don't yet know whether that's a really meaningful pattern.

The sample size from each location is still so small, and so many towns and villages haven't been touched, that we can look forward to a much clearer, higher-resolution picture in the future. Data from the Sicily DNA Project should be jointly analyzed with the Di Gaetano data for a start.