The Genetic History of France

Angela

Elite member
Messages
21,823
Reaction score
12,327
Points
113
Ethnic group
Italian
Thanks to Iosif Lazaridis for the link via his twitter account.
See:
Aude Saint Pierre et al
https://www.nature.com/articles/s41...eWZqzh_wWxd3QbBaLb8tL1djT75g8su49oKgniUafWg==


Despite the fact that the clusters were created using only self reported geographical origin, and the modern sources are only the 1000 genomes data, the results make sense.

"[FONT=&quot]The French genomes were found to map at their expected position in between north-west Europe (GBR and CEU), Italian and Spanish individuals from the 1000 Genomes Project."

[/FONT]
"[FONT=&quot]An important division separates Northern from Southern France. It may coincide with the von Wartburg line, which divides France into “Langue d’Oïl” part (influenced by Germanic speaking) and “Langue d’Oc” part (closer to Roman speaking)—Fig S20. This border has changed through centuries and our north-south limit is close to the limit as it was estimated in the IXth century [47, 48]. This border also follows the Loire River, which has long been a political and cultural border between kingdoms/counties in the north and in the south (Fig. 1). Regions with strong cultural particularities tend to separate. This is for example the case for Aquitaine in the South-West which has long represented a civilization on its own. The Brittany region is also detected as a separate entity in both datasets. This could be explained both by its position at the end of the continent where it forms a peninsula and, by its history since Brittany has been an independent political entity (Kingdom and, later, duchy of Bretagne), with stable borders, for a long time [49]. The extreme South-Western regions show the highest differentiation with the neighboring 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. FST between the south-west and the other French clusters was markedly higher than the FST between remaining French clusters. In 3C these values are comparable with what we observed between the Italian and the north-west of Europe (FST = 0.0035). We observed similar trends 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” (Fig. 1). At a finer-scale, the “Adour” river partition the SW to the SO cluster in the 3C dataset. This alignment suggests moderate genetic isolation between riversides and might reflects isolation by resistance in which specific observed features such as river barriers (or altitude) influence connectivity. The Loire is a large, fierce river. Historically, at each slightly high flood it exceeded its banks and covered its valley over a width of several kilometers, leaving behind it, when it withdrew, mud and swamps. Such wide gap presents a serious obstacle to any kind of relations. The slope, even at the flattest part, is not lower than 0.2 m/km, three time more than for Seine River (Fig. S2). Similarly, the Garonne River also displays one of the fastest flow rates and is characterized by low number of fords and bridges: at least since Strabo, Garonne was a border between the Aquitans and Celtic Gauls [50]."

[/FONT]
"[FONT=&quot]However, the decrease we observe in the genetic data does seem to affect mainly the Northern part of France, and for instance is mainly observed in the NO cluster. We see no reason for this trend based on historical records (Fig. S21) except perhaps the last plague epidemics in 1666–1670 that was limited to the NO of France. Alternatively, a more diffuse population in the SO (which is in general hilly or mountainous) may explain a lower impact of these dramatic episodes. Plague is expected to have had a very strong impact on the population demography in the past as some epidemics led to substantial reduction in the population sizes [55]. However, we could not detect in our data any footprint of the Justinian plague (541–767 AD) although, according to historical records it had a major impact on the population at that time. This may be due to difficulty to estimate population changes in ancient times, deeper than 50–100 generations, especially in presence of more recent bottleneck and given our reduced sample sizes in some of the groups and IBD resolution power. We expect that increasing sample size especially for the FineSTRUCTURE subgroups with small sample sizes will help getting more detailed information farther in the past."

[/FONT]
The graphics make all of this even clearer.


uYuf3ed.png

It's the Garonne which separates the two areas of southwestern France.

It's also clear why the Lyon sample, for so long the only French academic sample, was so northern shifted, and why the "Aquitaine" sample was so different. I'd love to see what the southeastern samples look like. Hopefully, they'll release them.

As for the next graphic, I would have expected there to be a demarcation along the Rhone.

uuKsYGA.png


Hwh2vsw.png


LVG9BQ3.png


Once again, the European farmer is the largest single component, over 60% in all of France except for Brittany, where it is close to 50%.
 
Why would you expect there to be a perfect correlation between yDna and autosomal dna?

Surely everyone should know by now that it doesn't always exist.

Plus, in general terms it's a question of different types of R1b.
 

This thread has been viewed 2230 times.

Back
Top