- Human pathology

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Wednesday 28 September 2005

- Approximately 10 miles separate the Horn of Africa from the Arabian Peninsula at Bab-el-Mandeb (the Gate of Tears). Both historic and archaeological evidence indicate tight cultural connections, over millennia, between these two regions. An important gene flow occured across the Red and Arabian Seas.

- Nine distinct subclades, including three newly defined ones, were found to characterize entirely the variation of Ethiopian and Yemeni subhaplogroup L3 lineages.

- Both Ethiopians and Yemenis contain an almost-equal proportion of Eurasian-specific haplogroup M and haplogroup N and African-specific lineages and therefore cluster together in a multidimensional scaling plot between Near Eastern and sub-Saharan African populations.

- Phylogeographic identification of potential founder haplotypes revealed that approximately one-half of haplogroup L0-L5 lineages in Yemenis have close or matching counterparts in southeastern Africans, compared with a minor share in Ethiopians.

- Newly defined subhaplogroup L6, the most frequent haplogroup in Yemenis, showed no close matches among 3,000 African samples, highlighting the complexity of Ethiopian and Yemeni genetic heritage.

- The introduction of maternal lineages into the South Arabian gene pool from different source populations of East Africa is consistent.

- A high proportion of Ethiopian lineages, significantly more abundant in the northeast of that country, trace their western Eurasian origin in haplogroup N through assorted gene flow at different times and involving different source populations.

- Sub-Saharan African maternal origin

  • More than a third of Yemen Hadramawt were of clear sub-Saharan origin. (12629598)
  • Other Arab populations carried approximately 10% lineages of sub-Saharan origin, whereas non-Arab Near Eastern populations, by contrast, carried few or no such lineages, suggesting that gene flow has been preferentially into Arab populations. (12629598)
  • Most of this gene flow probably occurred within the past approximately 2,500 years. (12629598)
  • However, there is little evidence for male-mediated gene flow from sub-Saharan Africa in Y-chromosome haplotypes in Arab populations, including the Hadramawt. (12629598)
  • Results are consistent with substantial migration from eastern Africa into Arabia, at least in part as a result of the Arab slave trade, and mainly female assimilation into the Arabian population as a result of miscegenation and manumission. (12629598)


- Richards M, Rengo C, Cruciani F, Gratrix F, Wilson JF, Scozzari R, Macaulay V, Torroni A. Extensive female-mediated gene flow from sub-Saharan Africa into near eastern Arab populations. Am J Hum Genet. 2003 Apr;72(4):1058-64. PMID: 12629598

- Kivisild T, Reidla M, Metspalu E, Rosa A, Brehm A, Pennarun E, Parik J, Geberhiwot T, Usanga E, Villems R. Ethiopian mitochondrial DNA heritage: tracking gene flow across and around the gate of tears. Am J Hum Genet. 2004 Nov;75(5):752-70. PMID: 15457403