Basque genetic distinctiveness (again)

By Razib Khan | December 28, 2011 11:05 pm

With all the talk about Basques I decided to do my own analysis with Admixture. Dienekes gave me a copy of his IBS file, which has all the 1000 Genomes Spanish samples, including Basques. I merged it with the HGDP sample, which has French Basques (just “Basques” in the plots below) and French non-Basques. I pruned most of the populations, but kept the Mozabites, which are a Berber group from Algeria. The number of markers was ~350,000, and I ran it up to K = 8, or 8 component populations. I stopped there because the components were starting to break up in a very choppy manner.

In general I do think that the idea that non-Basque Spaniards have Moorish genetic input seems supported. It isn’t definitive though. And you have to be careful, there are lower parameter values where Sardinians seem to have an affinity with Mozabites to a great extent, even more than Spaniards. But that disappears as you move up the number of K’s. But who is to say which K is the correct K? The consistent Sub-Saharan African among non-Basque Spaniards (also evident in the Behar et al. data set) component probably convinces me that there was a Moorish impact, since these are likely to have come with the Islamic conquest, and not Phoenicians.

All the files from the Admixture run (and csv files with tabular results) are here.

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CATEGORIZED UNDER: Personal Genomics
MORE ABOUT: Admixture, Basques
  • Dwight E. Howell

    Considering the fact the Moors ran most of what is now Spain for some time some impact seems logical but then if the markers you are looking at could have come from the Phoenicians ruling them out seems high risk. These people dealt with the coastal part of what is now Spain for a long time and they ran part of North Africa for a long time.

    Any attempt to sort that out would require doing extensive research on preconquest remains both in North Africa and in what is now Spain. This will most likely be done in time…

  • http://dienekes.blogspot.com Dienekes

    The Mozabites are an ancient blend (>100 generations) between Caucasoids and an African element.

    http://dienekes.blogspot.com/2011/04/comparing-five-methods-of-admixture.html

    The Caucasoid element is most similar to the element that is modal in Sardinians and Basques.

    Non-Basque admixture with Mozabites is above that of other Europeans, which suggests that there is indeed some remnant of NW Africans there

    https://docs.google.com/spreadsheet/ccc?key=0ArJDEoCgzRKedGdRbkxKMDdlZkJWc21tdkpldWxwVmc#gid=0

    Which amounts to 3-4% in Spain and about double in Portuguese Dodecad participants. Within Spain itself there is no very strong difference in the levels of this component, except in the case of Basques that seem to lack it altogether.

  • Elfino

    I am spanish. As far as I know, moors didn’t integrate with spaniards, there was a conversion to islam of the habitants of the iberian peninsula (Of course, probably there was some mixing).

    I think that the influence from north Africa could come from roman (think on the slaves from all the roman empire that came to spain) and prerroman times. But you would have to test spanish tombs of V AD…

  • Miguel Madeira

    When I was in high school, the “dominant theory” in my History teachers was that Iberos (the inhabitants of the Iberia before the Celts) were from North Africa; these could explain the high “north-african” genes in spaniards, but could be contradictory with the almost absence of this genes in Basques)

  • http://forwhattheywereweare.blogspot.com/ Maju

    When I read the title I thought you had made an Iberian-only analysis. Seems not.

    “In general I do think that the idea that non-Basque Spaniards have Moorish genetic input seems supported”.

    The apportion of North African component in Iberians is small (in contrast the European component in North Africans is much more marked): I get 2.3% for the Spaniard sample, what is nearly nothing considering the geographic proximity. It’s probable however that this component has a West-East cline, with larger apportions among Portuguese, Galicians, westernmost Spaniards in general, as suggested by the cline of haploid DNA (Y-DNA E-M81 and mtDNA U6 and L(xM,N)).

    This cline cannot have been produced by the Islamic period but can well have been caused by a Neolithic or even Paleolithic founder effect.

    IF you’d run only the IBS sample and a Moroccan control, you’d see if the cline of “Moorishness” goes West to East, as I expect, or not.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    IF you’d run only the IBS sample and a Moroccan control, you’d see if the cline of “Moorishness” goes West to East, as I expect, or not.

    the henn et al. overlaps with dienekes’ IBS at only 27,000 markers :-( though PCA might work.

  • http://forwhattheywereweare.blogspot.com/ Maju

    Does not need to be Moroccan, Mozabites… even Canarians might do (although an unmixed/less mixed North African sample would be better). I can even imagine that the component would eventually show up at some K-depth alone if you run only Iberian samples (better without Basques), as this component could be 5-10% in some areas (West), based on Y-DNA specially.

    In any case, as I have said before, haploid genetics do not suggest any correlation of North African genetic influence with the Muslim period, because some of the areas with greater “North African” Y-DNA (and also mtDNA as far as I know) are precisely the very core of the Christian Reconquista: Galicia, Asturias, León, Cantabria, Northern Portugal, and not at all the last stand of the Moors (East Andalusia). See Adams 2008 for greater detail.

    As some Spanish commenters have mentioned, most Andalusi Muslims were Iberian converts (and many Andalusis were not even Muslim at all). After all North Africa had been conquered just a few years earlier and was not even properly converted at the time (that happened mostly under the “Taliban” rule of Almoravids and Almohads, two vaguely related fanatic groups). There was some Berber influence in some taifas of coastal Andalusia (Málaga and Almería notably had Berber dynasties, while Valencia and Denia had “Slavic” Muslim dynasties but all the rest had Andalusi, i.e. Iberian dynasties).

    The North African element must have another older origin. I suspect two scenarios: Neolithic founder effect after Cardial “bounce” in North Morocco or Paleolithic backflow in the context of the Oranian (Iberomaurusian) genesis, which probably brought a lot of Iberian blood to North Africa (some 25% of mtDNA and some 10% of Y-DNA, and maybe 5-25% of autosomal DNA, are surely of Iberian origin).

  • Grey

    K-values

    It seems to me there’s two ways of looking at this. You can view every geographically bounded population (nation) as a unique element or view them as a unique compound of a potentially quite limited number of major elements that exist like tectonic plates under the surface.

    I may not understand it right but it seems to me that if the latter case is more correct then as you raise the K value at first you will identify the major components but as you raise it more you run the risk of slipping over into identifying the most unique blends or (uniquely unblended) i.e. are Basques a unique component or are they a uniquely unblended representative of one of the other major components?

    Moors in Spain

    If you have elite conquest then the winners will be living in the castles and palaces and will have servant girls from the conquered population and will have children with them. I don’t think there will ever be an exception to that rule. However it does seem in many places the genetic consequences of elite conquest are smaller than might be expected.

    Some possible explanations:

    1) Volk or military elite: If the conquerors bring their wives they’ll have full blooded legitimate children and half-blooded illegitimate ones. If they don’t bring wives their legitimate and illegitimate children will be half-blooded from the start and their children’s illegitimate children will be quarter. I think this must make a dramatic difference.

    2) Pre-modern political elites were a military elite: The male line of the pre-modern political elite did a lot of getting killed. If you imagine a battle like Agincourt the modern equivalent might be like half the members of Congress losing a male family member in one battle. I think conquering elites in the past would have replenished by promoting junior ranks of their ethnic aristocracy to higher ranks and filling in the lower ranks from the conquered population or their more mixed illegitimate children. So after a few hundred years a Moorish Duke of Zaragossa might only be 1/8 Moorish.

    I think the recorded Norman experience in England is likely to be representative of a standard pattern. This may depend on how psycho the conquering elite are.

    3) Concentration and Massacre: Seiges often ended in massacre. If a conquering elite took over as the rulers of a town and surrounding countryside their genetic impact might be 3-4% outside the town and 20-30% inside. Then when the next conquering elite comes along and the town gets massacred most of the genetic impact goes too.

    4) Big initial massacre: Not very pleasant but if a 5% male elite conquers a terriotory and massacres the previous 5% male elite then even if they have 3 or 4 times as many descendents per head as the base male population that’s still only 15-20% impact. However if you’re Genghis and you replace the original 5% elite and massacre 50% of the rest then your group is suddenly 10% of the surviving male population and your long-term genetic impact will be doubled. (This is more a possible explanation of exceptions to the limited impact rule.)

  • Amanda S

    Another historical event to bear in mind was the seventeenth century expulsion of the Moriscos (descendents of the Moors converted to Christianity) from Spain.

    http://en.wikipedia.org/wiki/Expulsion_of_the_Moriscos

    This involved a large number of people. It didn’t occur in Portugal which might explain why Portugal has double the amount of North African admixture as Spain has.

  • Elfino

    There are communities in Spain that doesn’t integrate (unfortunatelly) with the rest of the people. For example, gipsies arrived to Spain in the XV th century, but even today I think there must be little influence in the rest of the iberian population.

    Amanda, I believe that Moriscos were descendants of iberian muslims (iberians converted to that religion), not from the north of Africa.

  • http://forwhattheywereweare.blogspot.com/ Maju

    @Amanda: I have discussed recently the “expulsion of the Moriscos” in a different debate and seems totally hyped. There were instances of actual ethnic cleansing but mostly all stayed as before, not the less because many converted and yet many others had never quit being Christians. Someone reads of some thousands and in his/her mind they become millions and the population of whole kingdoms… but the fact is that nothing happened that might have radically changed the genetic landscape in the end.

    “It didn’t occur in Portugal which might explain why Portugal has double the amount of North African admixture as Spain has”.

    There was forced conversion in Portugal as well and anyhow it does not explain why ALL Western Iberia has Portugal-like or greater North African component, including areas that should not at all (within this sadly hyper-simplistic frame that you spouse), like Galicia, Asturias, Cantabria and León. The North African component in Iberia must be at least Neolithic, when such founder effects were still possible.

    Elfino said:

    “Amanda, I believe that Moriscos were descendants of iberian muslims”…

    In most cases yes. While there must have been some flow, not just in the Muslim period but also before, between North Africa and Iberia, almost all Iberian Muslims were of Iberian origin, of course, while in North Africa there were many native Christian (usually Arian monophysite but also Catholic) and even Jews (Berbers of Jewish religion). The rather strict cultural-religion division we see today only began since the Almoravid/Almohad period, i.e. in the critical period of the Reconquista (and was then reinforced by massive forced conversion and acculturation that took quite many generations to accomplish).

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This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

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