Genetic study on North Africans

[Kamal900]

Genome-Wide and Paternal Diversity Reveal a Recent Origin of Human Populations in North Africa

PLoS One. 2013; 8(11): e80293.
Published online Nov 27, 2013.

"Early genetic studies have identified an Upper Paleolithic component in current northern African populations, and suggested that the Neolithic transition occurred through cultural diffusion [9], [10]. Studies using autosomal markers such as short tandem repeats (STRs), polymorphic Alu insertions, HLA class II polymorphisms, and GM and KM allotypes have shown close genetic affinity of North Africans to Eurasian populations and found evidence of gene flow from sub-Saharan populations [11]–[24]. Recent genome-wide analysis of North Africans found substantial shared ancestry with the Middle East, and to a lesser extent sub-Saharan Africa and Europe (see Figure S1 for a geographical description of the region). An autochthonous Maghrebi ancestry that increases from east to west across northern Africa was also identified. It was suggested that this ancestry likely derive from “back-to-Africa” gene flow more than 12,000 ya [25]. In addition, it has been suggested that recent gene flow between the Middle East and North Africa was probably promoted by shared cultures after the Islamic expansion, increasing genetic similarities between North Africans and Middle Easterners [26]. Interestingly, genome-wide analysis also shows that increased genetic diversity in Southern Europe, which is higher than in other regions of the continent, is a result of recent gene flow from North Africa [27]."

" In contrast to the Middle Eastern influence, studies have reported only limited contribution of sub-Saharan paternal lineages to the North African gene pool [39], [40]. Previous analyzes of mtDNA lineages in North African populations suggest significant Eurasian origins [41]–[43] with lineages dating back to Paleolithic times [41] and with recent gene flow from sub-Saharan Africa linked to slave trade [44]. mtDNA variations showed an East-West cline accompanied by a genetic discontinuity on the Libyan/Egyptian border, suggesting a differential gene flow in the Nile River Valley [45].\"

"The first two components account for 55.35% of the variation and reveal a strong geographical clustering of the populations analyzed (Figure 2A). The first component separates sub-Saharan Africans which have higher frequencies of B-M60 A-M91, E-M2, and E*-M96 haplogroups. The first component also shows clustering of the Europeans characterized by R*-M207 and I-M170 and Middle Easterners which have higher frequencies of E-M78, E-M123, J-M267, and J-M172. The second component separates all North African populations except Egyptians from all other populations and shows that E-M81 plays a major role in this structure. The Tuareg appear to be drawn towards sub-Saharans while Egyptians clustered with Middle Easterners close to Palestinians"


http://www.ncbi.nlm.nih.gov/pmc/arti...-0080293-g002/

"Genetic affinity between the studied groups was further investigated by calculating pairwise genetic distances (RST) using Y-STR haplotypes. The MDS (Figure 2B) shows a geographical clustering similar to the PCA. The first dimension splits the sub-Saharan Africans from all other populations. The North Africans cluster close to Middle Easterners with Tuareg drawn towards sub-Saharans and Egypt close to Palestinians."

"Results show significant variance among groups when Morocco, Algeria and Tunisia were pooled in one group and Libya, Tuareg, Egypt and the Middle East pooled in the second group. Variance among groups decreases but remains significant when Libyans and Tuareg are added to the first group. Conversely, significant differences between groups are lost when Egyptians are added to the North African group (Table S3). This result is also reflected in the PCA and MDS and shows Egypt's strong affinity to the Middle East rather than to North Africa."



"PCA on genome-wide SNPs (Figure 4A) shows that North Africans are diverse and closer to Middle Easterners and Europeans than to Sub-Saharan Africans. Egyptians appear the closest to Middle Easterners and Europeans while South Moroccans are drawn towards Sub-Saharans. Tunisian samples (Chenini-Douiret Berbers) form an orthogonal cluster close but distinct from other North Africans which mostly appear in overlapping clusters."


http://www.ncbi.nlm.nih.gov/pmc/arti...-0080293-g004/

"We constructed trees that infer population relationships using TreeMix [62]. This method estimates both population splits and the possibility of population mixture. First, we build a maximum-likelihood tree setting the position of the root at the Yoruba (Figure 4B). South Moroccans and Saharawi appear close to Yoruba while Egyptians are on a branch leading to Middle Easterners and Basque. Next, we set TreeMix to allow migration edges (m) and test by increasing m sequentially up to m = 20. The initial tree structure remains mostly unchanged when migration edges are added. All North Africans except Tunisians appear admixed from an ancestral population to Yoruba."

More --> http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3842387/

Whats your opinion about the study?

[Tooting Carmen]

So Arabs had much more genetic impact than did Black Africans then?

[Kamal900]

So Arabs had much more genetic impact than did Black Africans then?

The study suggests that paternally Arabians contributed their genetic lineages(paternally) while Black africans contributed their genes more in the maternal side. My people seem to be the closest to Egyptians than to Syrians and Lebanese in both dimensions.

[Yuffayur]

So Arabs had much more genetic impact than did Black Africans then?

No, it's neolithic rather than Arab.

[Yuffayur]

I hope they will post a (new) macro study in Northern Africans, rather than one with Morocco S and Morocco N, which does not mean anything, I hope they will use regional samples like Atlassian, Middle atlassian, Oranian, Riffian, Kabyle, Chaouia, not a simple "Algeria" , "Tunisia", I hope they will do the same with Egypt, there are some studies in Eastern Africans and there are some samples from central and southern Egypt, btw the plots use Y-DNA distribution not admixture.

[Kamal900]

I hope they will post a (new) macro study in Northern Africans, rather than one with Morocco S and Morocco N, which does not mean anything, I hope they will use regional samples like Atlassian, Middle atlassian, Oranian, Riffian, Kabyle, Chaouia, not a simple "Algeria" , "Tunisia", I hope they will do the same with Egypt, there are some studies in Eastern Africans and there are some samples from central and southern Egypt, btw the plots use Y-DNA distribution not admixture.

What do you think of the PCA plot charts showing Egyptians being genetically the closest to us Palis than to other peoples? It would seem that Southern Moroccans have more SSA admixture than the northern ones, but i have seen one Mauritanian student in my class and he look very pale and caucasoid. Turegs seem to lean towards SSA because of black admixture in them(they are a mix between berbers and blacks).

[StonyArabia]

So Arabs had much more genetic impact than did Black Africans then?

It's neolithic, but the area with the greatest Arabian impact would be Libya. The Arabs had an impact on the paternal lineages, but this is more recent and traces to the 10th century, when the Shia Bedouin tribes invaded North Africa like the Banu Hilal. At this time time most of North Africa adhered to Shiaism, but the Zirid a Berber group broke away and became Sunnis, this angered the Fatamid Caliphs, so they enlisted the Banu Hial and other related Bedouin tribes to invade North Africa in this process. The Banu Hilal would be responsible for Arabization of North Africa, however due to being a minority they could not maintain their ethnic and sectarian affiliation, so they became assimilated with the numerous Berbers and became Sunnis themselves in the process but Arabization occured. Today the Banu Hilal influence is greatly found in culture, and to some extent bloodlines in Libya, as well the tribes that followed them. The more you go west the less the Arabian impact is, the more you go east it's more heavy.

[oblivion]

Wow so Egyptians are more near eastern than north african... Very interesting.. I plot with palis and even comes up as my top population in gedmatch along with bedouins. I am confused about libyans and the touareg tho.. How do they cluster more middle eastern?

[gold_fenix]

Oblivion you are copt not? Do copts are apart genetically of the common Egyptians?

[Isleño]

The study suggests that paternally Arabians contributed their genetic lineages(paternally) while Black africans contributed their genes more in the maternal side. My people seem to be the closest to Egyptians than to Syrians and Lebanese in both dimensions.

It seems to match the findings by a commercial study from DNA Tribes. The autosomal breakdown of the North African component is described in many sources as an ancient back migration that is 20,000 years old, but also possibly some from later migrations. In the screenshots below, the Levantine/Arabian component is representative of this ancient Caucasoid back migration: