Haplogroup BT

Haplogroup BT
Possible time of origin	70,000-80,000 years BP
Possible place of origin	Africa
Ancestor	A2-T
Descendants	B-M60, CT
Defining mutations	Page65.1/SRY1532.1/SRY10831.1, M42, M91, M94, M139, M299, P97, V21, V29, V31, V59, V64, V102, V187, V202, V216, V235

Haplogroup BT M91 also known as Haplogroup A1b2 (and formerly as A4, BR and BCDEF) is a Y-chromosome haplogroup. BT is a subclade of Haplogroup A1b (P108) and a sibling of Haplogroup A1b1 (L419/PF712).

Macrohaplogroup BT has been found in populations on every continent, since prehistoric times. It is the parent of Haplogroups B and CT. However, the basal paragroup BT* has not been found in modern populations.

The ISOGG tree since 2014 has treated M91 as the defining mutation of BT.

Prior to 2002, there were in academic literature at least seven naming systems for the Y-Chromosome Phylogenetic tree. This led to considerable confusion. In 2002, the major research groups came together and formed the Y-Chromosome Consortium (YCC). They published a joint paper that created a single new tree that all agreed to use.

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