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Thread: Fine Scale population structure of Spain and genetic impact of historical invasions

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    2 members found this post helpful.

    Fine Scale population structure of Spain and genetic impact of historical invasions

    The authors claim that the NorthWest African can be dated to the Moorish period. We'll see; I'm pretty skeptical about dating methods.

    Fine scale population structure of Spain and the genetic impact of historical invasions and migrations.


    Authors:
    C. Bycroft1 ; C. Fernandez-Rozadilla1,2 ; A. Carracedo2 ; C. Ruiz-Ponte2 ; I. Quintela-García3 ; P. Donnelly1,4 ; S. Myers1,4



    Institutes
    1) Wellcome Trust Centre for Human Genetics, University of Oxford; 2) Galician Public Foundation of Genomic Medicine (FPGMX)-Grupo de Medicina Xenómica-Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERer)-Universiy of Santiago de Compostela, Spain; 3) Grupo de Medicina Xenomica, Universidade de Santiago de Compostela, Centro Nacional de Genotipado – Plataforma de Recursos Biomoleculares y Bioinformaticos – Instituto de Salud Carlos III (CeGen-PRB2-ISCIII); 4) Department of Statistics, University of Oxford, 1 South Parks Road, Oxford, OX1 3TG, UK.


    Abstract:
    "As well as being linguistically and culturally diverse, the Iberian Peninsula is unusual among European regions in that its demographic history includes a prolonged and large-scale occupation by people of predominately north-west African origin. Therefore, the Iberian Peninsula provides a unique opportunity for studying fine-scale population structure and admixture, and to test cutting-edge methods of detecting complex or subtle population genetic patterns.Previous studies using Y-chromosome, mtDNA as well as autosomal data have detected limited genetic structure in Iberia. However, powerful new methods and larger datasets mean it has recently become possible to detect and characterise genetic differentiation at a sub-national level. We performed the largest and most comprehensive study of Spanish population structure to date by analysing a dataset of ~1,400 Spanish individuals typed at ~700,000 SNPs. Using the fineSTRUCTURE method we detected striking and rich patterns of population differentiation within Spain, at scales down to tens of kilometres. Strikingly, the major axis of genetic differentiation in Spain runs from west to east, while conversely there is remarkable genetic similarity in the north-south direction.To infer details of historical population movements into Spain, we analysed Spain alongside a sample of ~6,000 individuals from Europe, North Africa, and sub-Saharan Africa. Across Spanish groups, we identify varying genetic contributions from north-west African ancestral populations, at times that all fall within the period of Islamic occupation. We also identify Basque-like admixture within Spanish groups to the south of the Basque-speaking region, implying southerly gene flow from this region. This analysis has revealed details of the strengths and weaknesses of different approaches to investigating population genetic history, as well as providing important new insights into the complex genetic history of Spain."


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    Some of that northwest african can be from the moorish period but surely not for the most part since it has no north/south pattern like it should have.Let us look at portugal, if the northwest african admixture was from the moorish period we would see that admixture mainly in the south(alentejo and algarve) and it is not what happens, in fact it is quite widespread throughout the country, the amount of that northwest african is actually bigger in southerners in values of 3-4% in some cases maybe 1% maximum I would atributte to moorish ocupation since the theory of that amixture is that it is very old and since it came from north africa it is to expect that it would leave more impact in the south closer to africa than in the north.

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    Angela, will it be discussed in Baltimore October 6-10?

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    Quote Originally Posted by Pax Augusta View Post
    Angela, will it be discussed in Baltimore October 6-10?
    Wednesday, October 7th is the date for the presentation:
    https://ep70.eventpilotadmin.com/web...HG15&id=211117

    I don't think there's usually much discussion involved.

    With the Reich Lab papers, they usually go online before publication date, but a lot of academics don't do that, usually, I think, because the publications demand that it be on a pay per view basis for a while. So, it may be a while until we get access.

    @suebiking,

    I'm interested to see their evidence and reasoning. They're obviously aware, as can be seen from the abstract itself that the variation in Spain is east/west, not north/south.
    " Strikingly, the major axis of genetic differentiation in Spain runs from west to east, while conversely there is remarkable genetic similarity in the north-south direction."

    I'd also be careful in how to interpret these findings. No one should be surprised that, if you drill down deep enough, to small enough amounts of variation, you'll be able to find diversity in any country. That's what the POBI study of the British Isles discovered...the differences are very small, as they stated, but they do exist.

    Levels of genetic variation are relative. There's no comparison, for example, between the amount of genetic variation in Spain versus the amount of genetic variation in Italy. Any PCA would tell us that...just look at the amount of sheer "space" that is needed to contain all of Italian variation.

    "

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    Yes indeed, I give them merit for that, maybe befora the reconquista there some major differences between north and south but with the repopulation events most of that difference vanished. In contrast the difference between east and west didn't disappear, I sincerely believe that the major difference between east and west is the migration from north africa that did not affect the east so much also we got to take into account that the most untoutched areas since the neolithic are in the east. In my point of view this north west african is what makes the west iberian genome so unique although if this migration is indeed neolithic or even mesolithic I think it is safe to say that those are now tipycal iberian genes, it is just labeled north-west african because it is more present there these days, right?

    Now, I don't want to ge off-topic but allow me to ask, west iberians these days have around 6% of this northwest african admixture so this migration would have to be huge in numbers, do we have any arqueological proof of this, surely a migration from the mahgreb to europe would be accompanied by new technology, is it possible that it could be related with the foundation of "La Almagra Pottery Culture"?

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    Quote Originally Posted by suebiking View Post
    Yes indeed, I give them merit for that, maybe befora the reconquista there some major differences between north and south but with the repopulation events most of that difference vanished. In contrast the difference between east and west didn't disappear, I sincerely believe that the major difference between east and west is the migration from north africa that did not affect the east so much also we got to take into account that the most untoutched areas since the neolithic are in the east. In my point of view this north west african is what makes the west iberian genome so unique although if this migration is indeed neolithic or even mesolithic I think it is safe to say that those are now tipycal iberian genes, it is just labeled north-west african because it is more present there these days, right?

    Now, I don't want to ge off-topic but allow me to ask, west iberians these days have around 6% of this northwest african admixture so this migration would have to be huge in numbers, do we have any arqueological proof of this, surely a migration from the mahgreb to europe would be accompanied by new technology, is it possible that it could be related with the foundation of "La Almagra Pottery Culture"?
    The genes are "North African" in the sense that they "match" genes found in North Africa, no matter when they arrived. That doesn't mean that these aren't percentages typical of Spaniards.

    One of the reasons it's difficult to tell how much influence went from North Africa to Iberia or vice versa is because the changing climate has covered a lot of the remains with sand. It's certainly possible there was some exchange both ways in the Mesolithic and the Neolithic.

    If they've been able to date the gene flow, that will answer a lot of questions. That was one of the problems with the Botigue et al study: they didn't use Roll Off or Alder to date the admixture.
    http://www.pnas.org/content/110/29/11791.abstract
    http://dienekes.blogspot.com/2013/06...and-north.html

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    Quote Originally Posted by Angela View Post
    The genes are "North African" in the sense that they "match" genes found in North Africa, no matter when they arrived. That doesn't mean that these aren't percentages typical of Spaniards.

    One of the reasons it's difficult to tell how much influence went from North Africa to Iberia or vice versa is because the changing climate has covered a lot of the remains with sand. It's certainly possible there was some exchange both ways in the Mesolithic and the Neolithic.

    If they've been able to date the gene flow, that will answer a lot of questions. That was one of the problems with the Botigue et al study: they didn't use Roll Off or Alder to date the admixture.
    http://www.pnas.org/content/110/29/11791.abstract
    http://dienekes.blogspot.com/2013/06...and-north.html
    If I remember correctly there was a bit of North African (or was it SSA) admixture in WHG and SHG, at least in some of them. This points to some Mesolithic flow.
    There is also a suspicion that second wave of farmers, the one with domesticated animals, entered Iberia from West Africa. Pointing to some Early Mesolithic gene flow from there.
    Be wary of people who tend to glorify the past, underestimate the present, and demonize the future.

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    Quote Originally Posted by Angela View Post
    If they've been able to date the gene flow, that will answer a lot of questions. That was one of the problems with the Botigue et al study: they didn't use Roll Off or Alder to date the admixture.
    http://www.pnas.org/content/110/29/11791.abstract
    http://dienekes.blogspot.com/2013/06...and-north.html
    But fortunately Lazaridis et al. did, and they found African admixture in Spain to date from many generations before Islam even existed. Even Moorjani et al. found it was pre-Islamic, but unlike Lazaridis et al. the authors of that paper amazingly enough tried to argue that it was due to events from Islamic times despite the fact that their own dating contradicts this claim.

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    Well let's just wait till some remains are tested, then we'll have our answers, let's hope that if found the dna is in good conditions for autosomal runs.

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