posted
I know this is not surprising but it was a good read for me. Goes along with whats been said on here and historical events that happened in that region.
Abstract
quote:Background: Recent genomic analyses suggest that the current North African gene pool was mainly influenced by population flow coming from the East that altered the genetic structure of autochthonous Berber populations. Such genetic flow has not been extensively addressed yet using North African populations of Middle-eastern origin as reference. Aim: To discern the Middle-eastern component in the genetic background of Tunisian Arabs, and evaluate the extent of gene flow from the Middle East into North African autochthonous Berber populations. Subjects and methods: We have examined 113 Tunisians of well-known Arabian origin from Kairouan region, using 15 autosomal Short Tandem Repeats (STRs) loci. Results: No deviations from Hardy-Weinberg equilibrium were observed, and all loci presented high levels of heterozygosity. Principal coordinate and STRUCTURE analyses were consistent in clustering together North African and Middle Eastern populations, likely reflecting the recent gene flow from the East dating back to the Arab conquest period. This demographic migration and the Arabisation process that submerged the original Berber language and customs seems to have be accompanied by substantial gene flow and genetic admixture. Conclusion: This study represents an additional step to obtain a comprehensive understanding of the complex demographic history of North African populations.
posted
Looking at Figure 2 here... Samples 6-8 represent Egyptians (Siwa Berbers, Arabs, and Copts). I observe that, in this particular graph, at k levels 1-2 they have quite a bit of ancestry similar to "sub-Saharan Africans". At k = 1, they have a lot of the red component that's ubiquitous in the SSA sample. Moving on to k = 2, the SSA-like component is blue instead of red, but it's still sizable in the Egyptian samples.
This is a bit different from most other studies I've seen in which modern Egyptians don't necessarily have more SSA-like ancestry than other North Africans. In this study on the other hand, at the first two k levels the SSA-like influence seems almost stronger in Egyptians than the rest of North Africa. How come?
Note that one of the samples representing "sub-Saharan Africa" is Somali.
Posts: 7169 | From: Fallbrook, CA | Registered: Mar 2004
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quote:Originally posted by Nodnarb: Looking at Figure 2 here... Samples 6-8 represent Egyptians (Siwa Berbers, Arabs, and Copts). I observe that, in this particular graph, at k levels 1-2 they have quite a bit of ancestry similar to "sub-Saharan Africans". At k = 1, they have a lot of the red component that's ubiquitous in the SSA sample. Moving on to k = 2, the SSA-like component is blue instead of red, but it's still sizable in the Egyptian samples.
This is a bit different from most other studies I've seen in which modern Egyptians don't necessarily have more SSA-like ancestry than other North Africans. In this study on the other hand, at the first two k levels the SSA-like influence seems almost stronger in Egyptians than the rest of North Africa. How come?
Note that one of the samples representing "sub-Saharan Africa" is Somali.
GOOD eye Nodnarb. I don't know why I did not catch that about the Egyptian one.
Again good eye.
Posts: 1900 | From: NY | Registered: Sep 2014
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posted
^ I'm waiting on someone like Swenet or beyoku, who really knows how to examine these things, to explain it better than I could. But personally, I think the inclusion of Somalis as one of the three SSA samples (the other two beings Namibians and Tanzanians) might have affected the results by making the Egyptians look more SSA-like in the lower k resolutions. If, say, Nigerians or Congolese had been used in place of the Somalis, that SSA component wouldn't appear so strong in the Egyptian samples (since those other populations were further removed from the indigenous Egyptians to begin with).
-------------------- Without data you are just another person with an opinion - Deming Posts: 12143 | From: When you have eliminated the impossible, whatever remains, however improbable | Registered: Jun 2007
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quote:Originally posted by Nodnarb: ^ I'm waiting on someone like Swenet or beyoku, who really knows how to examine these things, to explain it better than I could. But personally, I think the inclusion of Somalis as one of the three SSA samples (the other two beings Namibians and Tanzanians) might have affected the results by making the Egyptians look more SSA-like in the lower k resolutions. If, say, Nigerians or Congolese had been used in place of the Somalis, that SSA component wouldn't appear so strong in the Egyptian samples (since those other populations were further removed from the indigenous Egyptians to begin with).
No, K2 including SSA populations displays African and non-African clusters... Somali's & Tanzanians apparently Have a peculiar OOA distinction starting at K2, which should give you confidence in the overall results. Moreso, with the inclusion of YRI, you would only see a higher % membership of the African individuals if previous studies hold true...
I always thought that the SSA components in Egypt were always distinguishable in Principle component analysis, or at least, more precisely, cluster analysis (K2)... But regardless of all that, the most notable attribute of the loci observed is that they're A U T O S O M A L which is always a better indicator of admixture or clustering in general.
...also distinguishable is the coastal Moroccan cluster starting at K4, which is overlooked, strangely, but I guess its the "small sample size" (n=146; Khenifra + Doukkala).Posts: 1785 | From: New York | Registered: Jul 2016
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quote:Originally posted by the lioness,: It sounds like more plasticity denial
terrible attempt at instigating....
...I thought you've been doing this for a while. Lioness productions ain't producing it seems
Posts: 1785 | From: New York | Registered: Jul 2016
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posted
It was going to work until you stepped in and ruined it, stick to your K2, I got this
Posts: 43042 | From: , | Registered: Jan 2010
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posted
There is not a lot you can get with only 15 Autosomal STR in Structure/Admixture analysis.
Posts: 2463 | From: New Jersey USA | Registered: Dec 2007
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posted
the inclusion of Somalis as one of the three SSA samples (the other two beings Namibians and Tanzanians) might have affected the results by making the Egyptians look more SSA-like in the lower k resolutions. If, say, Nigerians or Congolese had been used in place of the Somalis, that SSA component wouldn't appear so strong in the Egyptian samples (since those other populations were further removed from the indigenous Egyptians to begin with).
Keep in mind that Somalis, are just as sub-Saharan as Zulus or Tanzanians. And the foundational settling of the Egyptian Nile Valley region was by sub-Saharan Africans. Course the Sahara itself is a moving target. Cultures now found south of the desert once were in place far to the north.
Posts: 5935 | From: The Hammer | Registered: Aug 2008
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quote:Originally posted by Nodnarb: ^ I'm waiting on someone like Swenet or beyoku, who really knows how to examine these things, to explain it better than I could. But personally, I think the inclusion of Somalis as one of the three SSA samples (the other two beings Namibians and Tanzanians) might have affected the results by making the Egyptians look more SSA-like in the lower k resolutions. If, say, Nigerians or Congolese had been used in place of the Somalis, that SSA component wouldn't appear so strong in the Egyptian samples (since those other populations were further removed from the indigenous Egyptians to begin with).
I agree with your assessment but think it should be balanced with Beyoku's comment; you might not see that play out at this level of resolution.
For instance, in the STRUCTURE analysis in the paper below, Egyptians are either in their own pattern (Egyptian sample) or in the northern Sudanese pattern (the Coptic sample) and are seemingly not particularly related to the Somali sample. PCA shows the same thing as far as Somalis (and this time, also northern Sudanese as a whole) seemingly not being more decisively related to modern Egyptians compared to other samples west of Somalia. In genome-wide analysis you would never see this lack of decisiveness.
Another thing you would never see in genome-wide analysis: in some of the analyses you can even see results that resemble DNA Tribes' odd results (e.g. modern Egyptian samples showing a completely unrealistic affinity with certain samples over others). It basically underscores what I said about not taking the Amarna report literally and why.
CORRECTION: In STRUCTURE the Egyptian sample from Egypt is also in the pattern that includes northern Sudanese (i.e. it's not just the Coptic sample that's in this pattern).
Posts: 8792 | From: Discovery Channel's Mythbusters | Registered: Dec 2009
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