Friday, January 8, 2016

Just how "African" & "West Eurasian" are Horn Africans like Somalis and Tigrinyas?

Alright, some of you who maybe revisiting this post will likely notice that it's nothing like it used to be. I've decided to pseudo-delete the old post by editing in new and more concise info. Partly because the way this post used to be felt a little too convoluted for its simplistic purpose.

Instead, I found that I managed to explain things much more comprehensively but also concisely to an acquaintance who was rather persistently inquiring about the exact West Eurasian admixture levels among Horn Africans such as Somalis and Tigrinyas:



That message above should serve as a good enough substitute to the majority of the meanderings found in the prior version of this post. It's much more "West Eurasian" centric than this post was originally meant to be but; you can just take the West Eurasian estimates discussed above and see the "African" elements as the rest of the ancestry, of course.

If anyone is interested in the ball-park admixture levels of several of the other Horn African samples we have nowadays then, to give you a simple idea of how admixed many of them are, here is the general cline in regards to West Eurasian ancestry levels in the Horn region among the groups whom we have samples from currently:


Anuaks<Gumuz<Aris<Borana Oromos<Wolaytas<Somalis~Certain Oromos<Xamir Agaws ("Afar")<Beta Israels~Certain Oromos<Amharas<Tigrinyas<Tigres~Bejas


I've thrown in Tigres because, despite them not appearing in any studies with autosomal DNA data, a friend managed to get his hands on one or two Tigre samples via 23andme and they seemed slightly more West Eurasian than Tigrinyas, much like the Beja samples from Dobon et al. did. So, the Tigre insertion above is just a guess based on what he showed me and the fact that Tigres are lowland semi-nomadic pastoralists (unlike other Ethiopian Semitic speakers) who are known to intermingle with Bejas whilst their language seems to have a Beja/North-Cushitic substratum. [1]

Nevertheless, whether or not Tigres are, on average, more West Eurasian than Tigrinyas will need to be corroborated by more samples in the future or a decent peer-reviewed study where the ethnic group is included.

Reference List:



Notes:

1. The reference list is strangely empty this time around because most of the data I referenced in that message I linked to can be found all over this blog or in the sources shared in the old version of this blog post which you now have a picture of. So... Help yourself.

2. You can use methods like "masking" in some f-stats, from what I recall, but even so... All three methods are ultimately not perfect without good reference samples. 

6 comments:

  1. Hey Awale, we've spoken on this before, but you still don't find a problem with your argument? At the moment there is no way to accurately discern the proportion of "Basal Eurasian" (BA) ancestry in any given population, without a useable BA genome; that would include groups in the Horn of Africa (HOA), accordingly, there is no way to tell how much of the BA in such populations arrived there in one or multiple pulses of gene-flow. If we were to assume that your numbers are correct, one can argue that Habeshas and Somalis are ~50% and ~40% Near Eastern, but to translate that into "Western Eurasian" (WE) is being disingenuous. Near Eastern acts more as a geographic code and is applicable to the "package" argument that you're making, while WE describes a specific ancestral population represented by the likes Western hunter-gatherers (WHG) and the UHG present in modern-SW Asians and to a lesser extent North Africans and Horners. BA is as distinct to WE than to East Eurasian populations like the Dai and Onge. So yeah Somalis might be ~40% Near Eastern but only a portion of that is Western Eurasian. I guess it comes down to the appropriate use of terminology.

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    1. I don't see what the issue is here, my old friend. I've explained this to you before and we were in agreement. I think you're too fixated on semantics like the term "West Eurasian".

      I am not using West Eurasian here as some sort of "genetic criterion based term". I.e. "Only European Hunter-Gatherers and/or Ancient North Eurasians count as West Eurasian. Anatolian Neolithics don't count because of Basal Eurasian..." I'm instead using it as a GEOGRAPHIC term. The Near East, discounting Egypt, is a part of West Eurasia:

      https://lh3.googleusercontent.com/JUoFToprWgcFfQZOwyG-fZI4ce4bDQl88X5Ka0N7om2In8w13tWI25eQ3SvEyafsQCb5=w287-h285-p-no

      The people who brought this ancestry to the Horn originally back-migrated from West Eurasia = this is ancestry from West Eurasia and most closely associated to modern "West Eurasians" such as Peninsular Arabians, but as I noted in the notes section; the actual "Eurasian" / European Hunter-Gatherer-related element in Horn Africans such as Somalis and the Tigrinya is likely much lower because of Basal Eurasian.

      I'm merely looking at the term "West Eurasian" as a GEOGRAPHIC term not some peudo-racialist terminology where you have to be part of some "pure line" (shared node between WHG, EHG & ANE for example) to fit. Nearly half of the ancestry in various Maasais is "Northeast African" or "Horn African" (these are principally GEOGRAPHIC terms, and many of their ancestors did come from this region and are most closely associated with many of its current inhabitants) but of course in more detail; "Horn African" in this context is a mixture as well of "East African/Nilo-Saharan-esque ancestry + West Eurasian ancestry" and in Horners' case "West Eurasian" itself is a mixture of what looks to be European Hunter-Gatherer-esque ancestry and Basal Eurasian but I utilize the term "West Eurasian" because:

      a) There was an obvious back-migration from this region that facilitated the presence of this ancestry in us
      b) The inhabitants of this region and North Africa, both ancient and modern, are the closest relatives of our "West Eurasian" side

      Simple as that. You're making a fuss out of nothing, my good man.

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    2. Do we know how much of the ENF ancestry is composed of Basal Eurasian and or European Hunter gatherer among Somalis?

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    3. No, we don't. But our West Eurasian admixture, for now, fits best with Neolithic Levantines and they seem to be about ~30% Basal Eurasian with the rest seeming to be European Hunter-Gatherer-LIKE ancestry.

      https://1.bp.blogspot.com/-He8KH5HoUL4/V2SipopvDiI/AAAAAAAAFBY/KiqCB6AK6NIjQXFVoQ18ADphFo2N-PzjQCKgB/s1600/BE.png

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  2. Hi sir i just saw the dna ancestry tet results of two different Somalis
    http://dna.ancestry.co.uk/ethnicity/F3BBE527-FFE6-4764-A3D5-AEBC5EEED714/share/01ab8935-d5a6-47c8-9876-22708a76f42e/ba2f5be6-3862-417c-aa4f-bfaf8a61dffc

    http://dna.ancestry.co.uk/ethnicity/F3BBE527-FFE6-4764-A3D5-AEBC5EEED714/share/01ab8935-d5a6-47c8-9876-22708a76f42e/ba2f5be6-3862-417c-aa4f-bfaf8a61dffc
    how do you interpret the North African ancestry
    and if we counted it as a mostly Eurasian component wouldn't that make the total count higher than the 60/40 percentage?

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    1. Ibrahim, apologies for the late approval. Anyway, I wouldn't confuse myself with services like 23andme or AncestryDNA. AncestryDNA in particular lacks proper Horn region reference samples (if I recall correctly) and thus produces rather funky results for whatever Somali or "Ethiopian" whom they sample and I'm not even sure about the make-up of their "Middle Eastern" cluster (could easily be some "African" there).

      Just stick to the kinds of results you see via various ADMIXTURE calculators (those in studies and those made by chaps like Davidski over at Eurogenes), formal stats and so on. They're more sound.

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