Haplogroup A-L1085, also known as haplogroup A0-T, is a human Y-DNA haplogroup. It is part of the paternal lineage of almost all humans alive today. The SNP L1085 has played two roles in population genetics: firstly, most Y-DNA haplogroups have diverged from it and; secondly, it defines the undiverged basal clade A-L1085*. A0-T has two primary branches: A-V148 (also known as haplogroup A0) and haplogroup A-P305 (haplogroup A1).
Origin
Many proposals for haplogroup A-L1085's origin suggest it was associated with the ancestral population of Southern Africa's hunter-gatherers. This is because haplogroup A-L1085 lineages are frequent among the San people. However, the A-L1085 lineages of Southern Africa are subclades of A lineages found in other parts of Africa, mostly among Nilotic peoples but also among other Africans. This suggests that A-L1085 lineages arrived in Southern Africa from elsewhere. The two most basal lineages of Haplogroup A-L1085, A-V148 and A-P305, have been detected in West Africa, Northwest Africa and Central Africa. Cruciani et al. 2011 suggests that these lineages may have emerged somewhere in between Central and Northwest Africa, though such an interpretation is still preliminary due to the incomplete geographic coverage of African y-chromosomes. Initial studies reported that Haplogroup A-L1085 lineages emerged around 60,000 years ago which was significantly more recent than TMRCA for mitochondrial DNA lineages which coalesce to between 150-200kya. Cruciani et al. 2011 with major restructuring of branches pushed back the root of the Y-chromosome tree to 142,000 years ago. In November 2012, a new study by Scozzari et al. reinforced "the hypothesis of an origin in the north-western quadrant of the African continent for the A1b haplogroup, and, together with recent findings of ancient Y-Chromosome lineages in central-western Africa, provide new evidence regarding the geographical origin of human MSY diversity".
Geographical distribution
Central Africa Haplogroup A-M13 has been observed in populations of northern Cameroon (2/9 = 22% Tupuri, 4/28 = 14% Mandara, 2/17 = 12% Fulbe) and eastern DRC (2/9 = 22% Alur, 1/18 = 6% Hema, 1/47 = 2% Mbuti). Haplogroup A-M91(xA-M31,A-M6,A-M32) has been observed in the Bakola people of southern Cameroon (3/33 = 9%). Without testing for any subclade, haplogroup A-L1085 has been observed in samples of several populations of Gabon, including 9% (3/33) of a sample of Baka, 3% (1/36) of a sample of Ndumu, 2% (1/46) of a sample of Duma, 2% (1/57) of a sample of Nzebi, and 2% (1/60) of a sample of Tsogo.
East Africa Haplogroup A-M13 is common among the Southern Sudanese (53%), especially the Dinka (61.5%). Haplogroup A-M13 also has been observed in another sample of a South Sudanese population at a frequency of 45% (18/40), including 1/40 A-M171. Haplogroup A also has been reported in 14.6% (7/48) of an Amhara sample, 10.3% (8/78) of an Oromo sample, 13.6% (12/88) of another sample from Ethiopia, and 41% of a sample of the Beta Israel (Cruciani et al. 2002), and important percentages are also shared by Bantus in Kenya (14%, Luis et al. 2004) and Iraqw in Tanzania (3/43 = 7.0% (Luis et al. 2004) to 1/6 = 17% (Knight et al. 2003)).
North Africa The subclade A1 has been observed in Libyan Berbers, while the subclade A-M13 has been observed in approximately 3% of Egyptian males.
Southern Africa One study has found haplogroup A in samples of various Khoisan-speaking groups with frequency ranging from 10% to 70%. This particular haplogroup was not found in a sample of the Hadzabe from Tanzania, a population occasionally grouped with other Khoisan groups due to the presence of click consonants in their language, but whose language was thoroughly demonstrated to be an isolate as unrelated to them as other languages by work by linguist Bonny Sands.
Europe Haplogroup A has been observed as A1 in European men in England. A Y chromosome has been observed also with low frequency in Asia Minor, in the Middle East and in some Mediterranean islands, among Aegean Greeks, Sicilians (0.2% of A1a in Capo d'Orlando and 0.5% of A1b in all the island), Palestinians, Jordanians and Yemenites. Without testing for any subclade, haplogroup A1b has been observed in a sample of Greeks from Mitilini on the Aegean island of Lesvos and A1b has been observed also on 0.1% of Iberian Jewish. The authors of one study have reported finding what appears to be haplogroup A in 3.1% (2/65) of a sample of Cypriots, though they have not definitively excluded the possibility that either of these individuals may belong to haplogroup B.
Subclade distribution
A-V148* (A0)*) A-V148 is one of two primary branches in A0-T.
A-P305* (A1*) Haplogroup A-P305* is largely restricted to parts of Africa, though a handful of cases have been reported in Europe and Western Asia. A-P305 is found at its highest rates in Bakola Pygmies (South Cameroon) at 8.3% and Berbers from Algeria at 1.5% and in Ghana. The clade also achieves high frequencies in the Bushmen hunter-gatherer populations of Southern Africa, followed closely by many Nilotic groups in Eastern Africa. However, haplogroup A's oldest sub-clades are exclusively found in Central-Northwest Africa, where it, and consequently Y-chromosomal Adam, is believed to have originated about 140,000 years ago. The clade has also been observed at notable frequencies in certain populations in Ethiopia, as well as some Pygmy groups in Central Africa. Haplogroup A-L1085 is less common among Niger–Congo speakers, who largely belong to the E1b1a clade. Haplogroup E in general is believed to have originated in Northeast Africa, and was later introduced to West Africa from where it spread around 5,000 years ago to Central, Southern and Southeastern Africa with the Bantu expansion. According to Wood et al. (2005) and Rosa et al. (2007), such relatively recent population movements from West Africa changed the pre-existing population Y chromosomal diversity in Central, Southern and Southeastern Africa, replacing the previous haplogroups in these areas with the now dominant E1b1a lineages. Traces of ancestral inhabitants, however, can be observed today in these regions via the presence of the Y DNA haplogroups A-M91 and B-M60 that are common in certain relict populations, such as the Mbuti Pygmies and the Khoisan.
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