Haplogroup A (Y-DNA)

In human genetics, Haplogroup A (M91) is a Y-chromosome haplogroup. Haplogroup A is localized to East Africa and Southern Africa and represents the oldest and most diverse of the human Y-chromosome haplogroups. It is believed to be the haplogroup corresponding to Y-chromosomal Adam.

It is common among the Khoisan people, including the Bushmen, which - together with its high diversity - suggests that it was their original ancestral haplogroup. For example, Knight et al. (2003) reported 12-44% presence of haplogroup A in various Khoisan tribes. Surprisingly, it was not found in a sample of the Hadzabe from Tanzania, who are traditionally considered as an ancient remnant of Khoisan people because of the presence of click consonants in their language. Yet it is present in high frequency in East Africa.

Semino et al. 2001 found haplogroup A in 10.3% of an Oromo sample and 14.6% of an Amhara sample from Ethiopia. Especially high frequency (41%) can be found in Ethiopian Jews (Cruciani et al. 2002) and important percentages are also shared by Bantus from Kenya (14%, Luis et al. 2004), a small sample of Iraqw from Tanzania (17%, Knight et al. 2003), and Fulbe from Cameroon (12%, Cruciani et al. 2002). However, the highest presence of haplogroup A in East Africa was discovered in a sample of the Sudanese population - 42.5% (Underhill et al. 2000).

It must be noted, however, that the subclade found in East Africa (A3b2) is different from those found in the Khoisan samples and only remotely related to them (it is actually only one of many subclades within haplogroup A). This finding suggests an ancient divergence of the East African group from the same ancestral population in the south.

In 2007, seven men from Yorkshire, England sharing a distinctive surname were identified as being from the A1 subgroup of haplogroup A. It was discovered that these men had a common male-line ancestor from the 18th century, but no previous information about African ancestry was known. The A1 subgroup is extremely rare. In addition to the seven Yorkshire men, only 25 living carriers of the A1 subgroup are known, all of West African ancestry.