Wednesday, August 8, 2018

Contemporary Corsican Y-DNA Sheds Light On Southern European Pre-History

Historical Background

Bernard's blog provides a capsule history of Corsica and then explores a new paper on its genetics:
The most widely accepted hypothesis is the colonization of the Corsican-Sardinian bloc from Tuscany during different ice ages. Thus the first colonization of Corsica can go back to the Mesolithic between 18,000 and 15,000 years. The oldest archeological evidence is the Mesolithic collective burial of Campo Stefano located in the south of Corsica. It is 8940 years old. Other Mesolithic sites are identified in the south-west Filitosa and southern Corsica, as well as in Sardinia. 
A major demographic change occurred in the Neolithic from the sixth millennium BC. The archaeological remains are carved stones and pottery of printed ceramics, cardial or Campaniform. 
The Corsican prehistory ends when the Greeks settle on the island building the city of Alalia in 565 BC. JC. The Greeks were followed by Romans, Vandals and Byzantines.
There were also early Iron Age Greek colonies in Italy and Southern France before the full ascendancy of the Western Roman Empire.

The genetic data recounted below suggests that the Romans, and even less so, the Vandals and Byzantines didn't appear to have had much of a demic impact on Corsica. Corsica was eventually claimed by France, the country which controls it today, and the demic impact of subsequent Northern Italian and French rulers also appears to have been modest, although broad similarities between Northern Italy, Southern France and Corsica could obscure these sources of admixture.
After being ruled by the Republic of Genoa since 1284, Corsica was briefly an independent Corsican Republic from 1755 until it was officially ceded by the Republic of Genoa to Louis XV as part of a pledge for debts in 1768. Due to Corsica's historical ties with the Italian peninsula, the island retains to this day many Italian cultural elements: the native tongue is recognised as a regional language by the French government. Corsica was ruled by various powers over the course of its history, but had several brief periods of self-government. 
Napoleon was born in 1769 in the Corsican capital of Ajaccio. His ancestral home, Maison Bonaparte, is today a significant visitor attraction and museum.
The Genetics of Corsica and its Vicinity

Bernard summarizes the findings of a new genetics paper on Corsica as follow:
Y chromosome DNA in Corsica shows several waves of populations. The oldest is characterized by the arrival of haplogroup I2 in the Mesolithic. Deep demographic changes in the Neolithic are identified by the presence of haplogroup G. The Copper Age sees the arrival of haplogroup R on the island. The difference in distribution of the two subclades R1b-U152 and R1b-U106 may correspond to the two groups of statue-menhirs erected in the Bronze Age and distributed to the north and south. The settlement of the Greek city of Alaria seems to correspond to the maximum frequency of haplogroup E1b-V13. 
Regarding relations between Corsica and Sardinia, the results of this study suggest two different genetic histories, Nuragic and TorrĂ©enne . The distribution of haplogroup G also suggests a continuity between southern Corsica and Sardinia, while that of haplogroup I suggests a distinction. Indeed the Corso-Sardinian block is characterized by a climatic contrast. The glacial sediments in northern Corsica suggest three glacial episodes, whereas these sediments are absent in Sardinia. It is reasonable to think that the first Mesolithic arrived in Sardinia, where the climate is more favorable, before joining Corsica when the temperature has softened.
From Bernard's blog via Google translate from French (emphasis and link re Alaria added) discussing Julie Di Cristofaro, et al., Prehistoric migrations through the Mediterranean basin shaped Corsican Y-chromosome diversity PLOS (2018). 

I largely concur with Bernard's analysis above, although the estimated date of Y-DNA R's arrival may be a bit early for what could have been an early Bronze Age arrival instead.

Some of the interesting points in the raw data pertain to Y-DNA in Provence and Tuscany which are used for comparison purposes (I've interlineated editorial commentary in brackets and added emphasis to some of Bernard's translated blog text. I've also made some minor translation corrections.)
Haplogroup R is the most common in Corsica with a value of 51.8%. This haplogroup reaches 90% in Provence and 45.3% in Tuscany. The subclade R1b-U152 is predominant, especially in North Corsica. Nevertheless the subclade R1b-U106 is present in South Corsica. In Europe, R1b-U152 is the most common in Switzerland, Italy, France and Western Poland. Early DNA studies have shown that haplogroup R has spread in Western Europe in the Copper Age and the Bronze Age. 
Haplogroup G has a frequency of 21.7% in Corsica and 13.3% in Tuscany. It is absent in Provence. The subclade G2a-L91 reaches 11.3% in Corsica and is absent in Tuscany. G2a-L91 and G2a-PF3147 reach their highest frequency in Sardinia and Southern Corsica. Early DNA studies have shown that haplogroup G spread in Europe with Neolithic farmers. 
Haplogroup J shows an intermediate frequency in Corsica (11.8%) between those of Provence (6.6%) and Tuscany (17.6%). The subclade J2a-M67 is homogeneous on the island with a TMRCA of 2380 years. [Ed. i.e. 430 B.C.E., which is in the early Iron Age.] Subclade J2a-Page55 is present in northwestern Corsica. 
Haplogroup E is mainly represented by its subclade E1b-V13. Its frequency in Corsica (5.5%) is intermediate between those of Provence  (3%) and Tuscany (10.4%). The diffusion of E1b-V13 is supposed to be related to the Neolithic expansion.  [Ed. E1b-V13, which is my Y-DNA clade, is the predominant Y-DNA E clade in Europe and probably arrived via Greece and the Balkans.]
Haplogroup I is present in Corsica under its two clades I1 (0.3%) and I2 (2.4%). It is absent in Provence and present in Tuscany: I1 (0.3%) and I2 (6.3%). Clade I1 is mainly present in Northern Europe [Ed. with a Neolithic era expansion.], while clade I2 is mainly divided into two subclades: I2-P37 and I2-M436. The latter is present mainly in the Balkans. Ancient DNA studies have shown us that I2 is associated with the Mesolithic in Europe. It is also present in the Neolithic especially in the south of France. The subclade I2-M26 found in 30% of the samples in Sardinia is very little present in Corsica. 
Haplogroup Q is present in Corsica with a frequency of 2.4%. He is absent in Provence and has a frequency of 0.6% in Tuscany. [Ed. A frequency of Y-DNA Q that high in Corsica is probably a founder effect. Y-DNA Q is quite rare in Europe.]
Bernard doesn't discuss the distribution of Y-DNA T-M70 which was also present, but this would appear to be a good candidate for a Cardial Pottery Neolithic source, based upon its distribution within Corsica and where Y-DNA T is found elsewhere.

The Y-DNA R1b-U152 distribution probably implies a Bell Beaker related source in these areas, which is notable as I had been unclear on the extent of Y-DNA R1b distributions in Switzerland, Southern France and Northern Italy (I admit that I had never really even wondered about its presence in Corsica).

As far back as attested history goes, Northern Italy was Italic (probably due to early Iron Age migrations) with an intrusive Etruscan migration as well in that time period. The earliest attested linguistic data for Southern France was that it was ruled by Celtic tribes, although there may have been Vasconic speakers in the far Southwest.

Bernard and I both think that Greek colonization in the early Iron Age is a more likely source of Y-DNA E1b-V13 in these populations than Neolithic era expansions something that also fits the relative frequencies in Provence and Tuscany. Y-DNA J and E1b-V13 likely arrived at around the same time., even though Y-DNA J is more widely distributed in Corsica than Y-DNA E1b-V13. This Greek colonization event could also be the source of some of the Y-DNA I2 in the sample.


Samuel Andrews said...

Seems like Corsica has a pretty similar Y DNA gene pool to Italy which makes it possible there's "recent" ancestry from Italy.

andrew said...

@Samuel Andrews It is certainly possible and it is fairly hard to say when certain DNA arrived.