In human genetics, Haplogroup E1b1a (M2) is a Y-chromosome haplogroup. From 2002 to 2008, it was known as Haplogroup E3a.

It can also be referred to with mutational nomenclature as E-M2.

Haplogroup E1b1a is mainly restricted to sub-Saharan Africa, where it reaches frequencies of over 80% in West Africa.^[1] Rosa et al. (2007) and others suggest that it likely originated in and expanded from West Africa within the last 20,000 to 30,000 years based on the fact that the frequency and diversity of E1b1a in this region are among the highest found.^[2][3]

E1b1a is barely observed in the Horn of Africa, North Africa, and Southwest Asia, where the E1b1b haplogroup dominates, and its small presence in those areas is generally attributed to the slave trade and/or the Bantu expansion.^[4][5]

E1b1a is the single most common Y-chromosome haplogroup among people of Sub-Saharan African descent both inside and outside of Africa. It is observed at frequencies of 58%-60% in African Americans.^[1] "Because it is also predominant in West Africa, many African-Americans also trace their genetic history to this line of descent. Members of this haplogroup can also be found in Great Britain." ^[6]

The evidence for an early expansion (or origin) into West Africa which is part of the Sudanese belt (a region south of the Sahara extending from western to central Africa) is more complex and perhaps involved a separate expansion. The tangible proof for a different expansion of E-M2 into West Africa from a Bantu Expansion is supported by previous studies which demonstrated that haplogroup E1b1a and its subclade haplogroup E1b1a7 also called E-M191, harbor opposite clinal distributions in the Sudanese Belt region, a finding that is at odds with the hypothesis of a Bantu Expansion of these two lineages in the area. For example, Haplogroup E1b1a7 has a frequency of 23% in Cameroon (where it represents 42% of haplotypes carrying the DYS271 mutation or E-M2), 13% in Burkina Faso (16% of haplotypes carrying the DYS271 mutation or(M2)) and only 1% in Senegal ^[7], whereas Haplogroup E1b1a* or E-M2 reaches its highest frequency (81%) in Senegal ^[8]. In other words, as you move to West Africa from west Central Africa the less subclade M-191 is found and the more M-2 is found, this lead Cruciani to concluded "A possible explanation might be that haplogroup E1b1a or E-M2 were already present across the Sudanese belt when the M191 mutation, which defines haplogroup E1b1a7, arose in central western Africa." ^{[9] [2]}

See also

• Human Y-chromosome DNA haplogroup

Notes

External links

• Distribution of E1b1a/E3a in Africa
• Spread of Haplogroup E3a, from National Geographic
• Haplogroup E Tree

ca:Haplogrup E3a del cromosoma Y humà