The Genetic History of France

[Lucas]

https://www.biorxiv.org/sites/all/libraries/pdfjs/web/viewer.html?file=/content/biorxiv/early/2019/07/24/712497.full.pdf


Abstract

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 cohorts. These clusters match extremely well the geography and overlap with historical and linguistic divisions of France. By modeling the relationship between genetics and geography using EEMS software, we were able to detect gene flow barriers that are similar in the two cohorts and corresponds to major French rivers or mountains. Estimations of effective population sizes using IBDNe program also revealed very similar patterns in both cohorts with a rapid increase of effective population sizes over the last 150 generations similar to what was observed in other European countries. A marked bottleneck is also consistently seen in the two datasets starting in the fourteenth century when the Black Death raged in Europe. In conclusion, by performing the first exhaustive study of the genetic structure of France, we fill a gap in the genetic studies in Europe that would be useful to medical geneticists but also historians and archeologists.


But sadly they use for regional data only information about place of birth in specific department. It is useless as such person could have parents from different corners of France.
Only people with four grandparents from department should be sampled.
So I don't think it will be very reliable.

[Lucas]

BTW borders of French regions used by me in LM Genetics maps are more or less in line with their regional clusters:)

https://i.imgur.com/2zGgw4W.png

from study:
https://i.imgur.com/SU87ZYX.png


So I think I should give to Central France region access to Atlantic and reduce SW and NW France respectively. And maybe area east of Lyon and north of Grenoble assign to NE-France.

[Western_French]

Very interesting article thanks for this.

"Only people with four grandparents from department should be sampled" -> Agreed and I am sure this is what they did even if it's not mentioned otherwise the study wouldn't make sense.

[Lucas]

Very interesting article thanks for this.

"Only people with four grandparents from department should be sampled" -> Agreed and I am sure this is what they did even if it's not mentioned otherwise the study wouldn't make sense.

No, they didn't. Read what I quoted.



For every individual, information on places of birth was available, either the exact location (3C 120 study) or the “département” (SU.VI.MAX).

Analyses were performed on individuals who were free of dementia or cognitive impairment by the time their blood sample was taken and who were previously genotyped. The geographical locations of individuals were defined according to the latitude and longitude of their place of birth, declared at enrolment.

BTW They use samples from medical studies, not collected for genealogical puproses.

Place of birth means nothing in modern times when people constantly move on for work. Maybe in central France poor departments most people are autochtonous but not in departments with bigger cities and industry (north and west) or on cote d'azur.

[J. Ketch]

What's the reason for that huge divide through the middle of the country?

From those maps it looks like the Roman influence in France may have been overstated by some.

[Imperator Biff]

Seems like Bretons are almost unadmixed IA Britons.
About damn time we get some studies done on France.

[Lucas]

What's the reason for that huge divide through the middle of the country?

From those maps it looks like the Roman influence in France may have been overstated by some.

You mean those black lines? There are rivers.

[Western_French]

No, they didn't. Read what I quoted.
They use samples from medical studies, not collected for genealogical puproses.

OK, makes the whole study very approximated then.

If the samples are from rural France and from old people, I would trust it more though.

Nowadays, in many parts of France like in the North-East or in the South, it's gettting complicated to get 100% native samples.

[Voskos]

So apparently from figure 4 we see that the southeast can be modelled around 40% british, 30% italy, 30% iberia. Whereas the soutwest can be modelled fully iberian.

[Lucas]

So apparently from figure 4 we see that the southeast can be modelled around 40% british, 30% italy, 30% iberia. Whereas the soutwest can be modelled fully iberian.

And north fully northern:)

[Voskos]

I was speaking about figure 4 with "sourcefind" method, whatever that means. The north itself shows from 20% up to 40% southern ancestry, mostly iberian.

[Lucas]

OK, makes the whole study very approximated then.

If the samples are from rural France and from old people, I would trust it more though.

I don't see such division regretabely.

To be clear I don't state that most people are from different departments than born. But at least substantial portion of them, especially in more industrious departments and with bigger cities which attract immigrants from other regions. And it could affect results.

Personally I trust more SW France results (without Bordeaux) and Central France, Brittany rather too.

[Peterski]

They should have used the same criteria as in the POBI project:

https://www.peopleofthebritishisles.org

[Lucas]

They should have used the same criteria as in the POBI project:

https://www.peopleofthebritishisles.org

Yes, but they don't.

It could be their political agenda. To show that France is big mix...

But at least with some margin of error results are showing the same division which I obtained checking Gedmatch (and academic) French kits in K36.

But I'm sure with strict sampling criteria division would be much more clear. I guess what is their northern France would be divided to Normandy and eastern part. But by using too much mixed kits it was impossible...

[Western_French]

"I trust more SW France results (without Bordeaux) and Central France, Brittany rather too." -> yes, they are the areas less affected by large immigration you are right.

[Leto]

Yes, but they don't.

It could be their political agenda. To show that France is big mix...

Then they may have included French-born Maghrebis and Blacks. In France there are many people with North African and SSA ancestry whose parents were born in France too.

[Peterski]

Not sure why they call this study genetic "history" if there are no ancient samples at all?

[Lucas]

Then they may have included French-born Maghrebis and Blacks. In France there are many people with North African and SSA ancestry whose parents were born in France too.

I think they weren't crazy but who knows:)
EDIT: there is info that only continental ancestry was preferred.

[J. Ketch]

You mean those black lines? There are rivers.
If the river is the main reason for the divide, it would imply that such a divide goes back to the Beaker and Celtic migrations, not some massive Roman transformation of the population as has been alleged.

[Lucas]

Not sure why they call this study genetic "history" if there are no ancient samples at all?

Maybe it will be published full version with ancient samples for comparison? It is preprint on biorxiv only now.

[Lucas]

If the river is the main reason for the divide, it would imply that such a divide goes back to the Beaker and Celtic migrations, not some massive Roman transformation of the population as has been alleged.

You could be right.

Also we can add Rhone river (not drawed) which separate on the map SE cluster from other.

https://i.imgur.com/d8q3Oh0.png

[Lucas]

Although north eastern French results are less reliable (many immigrants form other regions) it is visible that Franconian expansion correlate with those maps.

And I guess Tuscan-like ancestry in SE France is partly autochtonous. If it could be only Roman why onyl there? We shoould see that also in other regions where were Roman cities.

[Western_French]

It's time to make a proper study with 100% autochthonous samples from each departement across the country. In the end, this study looks like a low-cost one but not totally reliable. Soon, it will be too late as that kind of samples won't exist anymore (apart from cemeteries), and we all know France will never allow to dna extraction from cemeteries.

[dududud]

Sampling is no worse than in the English PoBI ​​study. Even the criterion of 4 grandparents does not guarantee problems of sampling; to get around the problem, Aude St Pierre & her colleagues chose to use two cohorts chosen on different criteria: this is the principle of double randomized; everything is indicated in the study

https://twitter.com/genotepes/status/1252612865888059400