A rather decent analysis of French autosomal genetics has been privately pre-published recently (thanks to Jean Secques for calling my attention to it and to the lead author for making it available online).
Aude Saint Pierre et al. The fine-scale genetic structure of the French population. Submitted to the American Journal of Human Genetics in 2015. Freely accessible → ref. LINK, direct PDF link.
A highlight of the study is that the samples all belong to people born in the 1930s and locations refer to their place of birth, so the results should be reflecting the historical demographics of the French Republic in the early 20th century.
There are no supplemental materials available at this point, so it's only possible to get a glimpse of the general results and we can't go too much into fine detail. These general results are anyhow interesting. Let's see:
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| Figure 6: Prediction of geographic location of individuals from the test set (n=3,733) using multiple linear regression model. A) Expectation: The seven geographical regions of France according to the geographical coordinates of individuals in the test sample; B) Prediction of geographical coordinates according to the multiple linear regression model. |
This figure alone synthesizes the findings: most French citizens cluster in a single unit, which geographically would correspond to NE France (GE region), only SW French (Gascons and Basques mostly) deviate very clearly and roughly fit their own geography towards the Bay of Biscay (or Bay of Gascony, as the French call it). Some samples from the SE (MED and RA regions) also follow this trend. A few outlier samples from the East (GE, RA) look rather Rhenish German, although the lack of controls from outside the Hexagon does not allow me to confirm this appearance.
You may have noticed that I ignored the IDF samples but that is because it is the Paris region (Île-de-France), which was already back in the 1930s too cosmopolitan to be informative. That is of course reflected in all the results with "orange" dots being nearly of all affinities.
Follow the principal component analyses, whose more salient information is again the peculiarity of Southwesterners, i.e. Gascons, Basques, and nearby populations.
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| Figure 2: The scatter plot of the first three PCs from PCA performed on the SNP genotype data of the 4,433 individuals from the 3 Cities study. Individuals are coloured according to the region where they were born. (Note: the legend corresponds to both PCAs) |
Other than the "Gascon" specificity, which takes over PC1, I'd say that PC2 shows an "anti-Mediterranean" tendency and that PC3 instead shows a "pro-Mediterranean" tendency. This I gather from the relative position of the "red" MED cluster. They both weight the same.
Interestingly there is a prominence of the GO region (Mid-West between the Seine and the Garonne) which may indicate some sort of "Armorican" or "Briton-like" specificity. In appearance it could melt both the "pro-" and "anti-Mediterranean" tendencies but without being able to discern the particular dots (ID and location), I cannot swear for that.
Much more clear is the "anti-Mediterranean" tendency of Gascons, Basques and allies when they are strongly detached from the main French cluster and instead they show a "pro-Mediterranean" tendency, overlapping at the extreme with the MED cluster, the closer they are to mainstream French. This happens in both PC2 and PC3.
Little more to say, honestly. Maybe that the small Eastern group of outliers prominent in "anti-Mediterranean" tendency in PC2 probably corresponds pretty well with the outliers of the first graph, which looked German-like. So I guess that the positive side of PC2 probably corresponds with a Northern European tendency.
Interested on what you have to say on this one very particularly, reader.
