Haplogroup A is the foundational Y-DNA lineage that connects all living human males.
In short: Haplogroup A is not a single genetic group but a catch-all for Y-chromosomes that predate the major migration out of Africa. It represents the deepest branches of the human family tree, with its most ancient lineages found exclusively in Africa, holding secrets to our earliest origins and deepest ancestral history.
Haplogroup A is defined by the absence of the M91 mutation, which characterizes the later haplogroup BT. Because it is a negative definition—essentially everything that is not BT—it encompasses all Y-chromosomal lineages that diverged between the most recent common ancestor of all living men, estimated at 270,000 years ago, and the emergence of BT roughly 140,000 to 150,000 years ago. This makes it the most basal group in the human patrilineal tree.
The geography of these lineages is heavily concentrated in Africa. While the oldest sub-clades are found in Central and Northwest Africa, modern frequencies are highest among the Khoisan hunter-gatherers of Southern Africa and various Nilotic groups in Eastern Africa. The discovery of the A00 lineage in 2013, sometimes called Perry's Y, pushed the estimated time depth of the haplogroup to approximately 275,000 years, aligning with the appearance of early anatomically modern humans like those found at Jebel Irhoud.
The distribution of these lineages has been significantly reshaped by history. The Bantu expansion, which spread the E1b1a haplogroup across much of the continent about 5,000 years ago, largely replaced earlier lineages. Today, haplogroup A persists primarily in relict populations like the Mbuti and Khoisan. While rare outside Africa, trace amounts have been identified in the Middle East, Europe, and among the African diaspora, including a notable 18th-century case in Yorkshire, England, where seven men sharing the surname Revis were found to carry the A1a subclade.
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Sources
- Summary by Intellect · source: Haplogroup A (Y-DNA)
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