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In human genetics, Haplogroup A is a Human Y-chromosome DNA haplogroup. Unlike all other Y-DNA haplogroups, it is not defined by a specific mutation, but as the foundational clade of the patrilineal lineage of contemporary human population, by definition rooted in this population's Y-MRCA (or "Y-chromosomal Adam"). Formerly also known as "clade I",〔A. Underhill, P. Shen, A.A. Lin, L. Jin, G. Passarino, W.H. Yang, E. Kauffman, B. Bonné-Tamir, J. Bertranpetit, P. Francalacci, et al. ''Y chromosome sequence variation and the history of human populations'', Nat. Genet., 26 (2000), pp. 358–361〕 bearers of extant sub-clades of haplogroup A are entirely found in Africa (or among descendants of recently extracted African populations), in contrast with the descendant haplogroup BT ("clade II-X") bearers of which participated in the Out of Africa migration of anatomically modern humans. The most basal subclades of haplogroup A are, by age of divergence, "A00", "A0", "A1" (also "A1a-T") and "A2-T". Haplogroup BT, ancestral to all non-African haplogroups, is a subclade of A2-T. ==Origin== (詳細はhaplogroup BT, i.e. defined by the absence of the defining mutation of that group (M91). By this definition, haplogroup A includes all mutations that took place between the Y-MRCA (estimated at some 200 kya) and the mutation defining haplogroup BT (estimated at some 80–70 kya), including any extant subclades that may yet to be discovered. Bearers of haplogroup A (i.e. absence of the defining mutation of haplogroup BT) have been found in Southern Africa's hunter-gatherers, especially among the San people. In addition, the most basal mitochondrial DNA lineages are also largely restricted to the San. But the A lineages of Southern Africa are more recently derived sub-clades of A lineages found in other parts of Africa. This suggests that A lineages arrived in Southern Africa from elsewhere.〔 (as PDF )〕 The two most basal lineages of Haplogroup A, A0 and A1 (prior to the announcement of the discovery of haplogroup A00 in 2013), have been detected in West Africa, Northwest Africa and Central Africa. Cruciani et al. (2011) suggest that these lineages may have emerged somewhere in between Central and Northwest Africa.〔 Scozzari et al. (2012) also supported "the hypothesis of an origin in the north-western quadrant of the African continent for the A1b (i.e. A0 ) haplogroup". 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Haplogroup A (Y-DNA)」の詳細全文を読む スポンサード リンク
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