New Genetic Study of the French

The study of the genetic structure of different countries within Europe has provided significant insights into their demographic history and their actual stratification. Although France occupies a particular location at the end of the European peninsula and at the crossroads of migration routes, few population genetic studies have been conducted so far with genome-wide data. In this study, we analyzed SNP-chip genetic data from 2 184 individuals born in France who were enrolled in two independent population cohorts. Using FineStructure, six different genetic clusters of individuals were found that were very consistent between the two cohortsl

Results of FineSTRUCTURE analysis reveal fine-scale population patterns within France at a very fine level that are very consistent in the two datasets (Figure 1). FineSTRUCTURE identified respectively 17 and 27 clusters in 3C and SU.VI.M.AX, demonstrating local population structure (Figure S2). Even though the sampling distributions of individuals varies slightly between datasets both analyses show very concordant partitions with a broad correlation between clusters and geographic coordinates. The major axis of genetic differentiation runs from the south to the north of France.

The extreme South-West regions show the highest differentiation to neighbor clusters. This is particularly strong in 3C dataset, where we even observe an additional cluster. This cluster is likely due to a higher proportion of possibly Basque individuals in 3C, which overlap with HGDP Basque defined individuals. The FST between the south-west and the other French clusters were markedly higher than the FST between remaining French clusters. In 3C these values are comparable to what we observed between the Italian and the British heritage clusters (FST=0.0035). Similar trends are observed in SU.VI.MAX even though the level of differentiation with the SW was weaker.

We also observe that the broad-scale genetic structure of France strikingly aligns with two major rivers of France “La Garonne” and “La Loire” (Figure 3). At a finer-scale, the “Adour” river partition the SW to the SO cluster in the 3C dataset.

While historical, cultural and political borders seem to have shaped the genetic structure of modern-days France, exhibiting visible clusters, the population is quite homogeneous with low FST values between-clusters ranging from 2.10-4 up to 3.10-3. We find that each cluster is genetically close to the closest neighbor European country, which is in line with a continuous gene flow at the European level. However, we observe that Brittany is substantially closer to British Isles population than North of France, in spite of both being equally geographically close. Migration of Britons in what was at the time Armorica (and is now Brittany) may explain this closeness. These migrations may have been quite constant during centuries although a two waves model is generally assumed. A first wave would have occurred in the Xth century when soldiers from British Isles were sent to Armorica whereas the second wave consisted of Britons escaping the Anglo-Saxon invasions37. Additional analyses, on larger datasets may be required to discriminate between these various models.

OsricPearl wrote:Absolutely. It's one of the reasons I find France so fascinating. It's the middle of Western Europe, both in a geographic sense and a genetic sense. ( I wonder what the eastern European equivalent would be, Poland?)


Any country that produces these two men as natives:


Is really cool. I think that France has the greatest visual variation of any country in western Europe, so it's only natural that it should have the greatest genetic variations. However, according to the study, they are still quite homogeneous.

Neon Knight wrote:^ It makes little sense that they can differentiate between Poles and other East Europeans, but not between French and Germans. Either they are not using the best available methods of analysis or their sample sizes are too small or too vague. But it would help if the samples from academic studies were made available to them.