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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 the haplogroup A1b1 (L419/PF712).[2]

Haplogroup BT
Y-DNA tree.GIF
Possible time of originabout 150-145,000 years ago[1]
Possible place of originpossibly Africa[2]
DescendantsB-M60, CT
Defining mutationsPage65.1/SRY1532.1/SRY10831.1, M42, M91, M94, M139, M299, P97, V21, V29, V31, V59, V64, V102, V187, V202, V216, V235

Macrohaplogroup BT has been found in populations on every continent, since prehistoric times. It is the progenitor clade of the paternal haplogroups B and CT (all members of haplogroup B or CT are members of BT, but not all members of BT are necessarily members of B or CT).

Sufficient data is not always available to determine which, if any, member haplogroup a Y chromosome in BT belongs to. For instance, a survey of Y chromosomes in over 2000 men from different parts of Africa[3] reported that 7.5% carried haplogroup BT(xDE, KT), i.e. were members of haplogroup BT but not DE or K; such a sample might or might not include members of haplogroups B, C, or F (excluding K), or some undiscovered branch(es) of BT belonging to none of these.

In ancient DNA, an Upper Paleolithic European (Gravettian), Vestonice15,[4] belonged to BT, but was not excluded from any subhaplogroup. Later Stone Age individuals excavated at Fingira Rock, Malawi, dated to around 6100 years ago (2/2 males), and at Mount Hora, Malawi, dated to around 8000 years ago (1/1 males), all belonged to Y haplogroup BT(xCT)[5] (i.e. they did not belong to haplogroup CT but may have belonged to haplogroup B).


The ISOGG tree since 2014 has treated M91 as the defining mutation of BT.[6]

  • B M60, M181, P85, P90
  • CT P9.1, M168, M294

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.

The revised y-chromosome family tree by Cruciani et al. (2011) compared with the family tree from Karafet et al. (2008). Cruciani et al. (2011) define BT via M91 and P97, and as a consequence, ISOGG has listed BT since February 2012, and treated M91 as defining mutation for BT since 2014.[7]

See alsoEdit


  1. ^ Kamin M, Saag L, Vincente M, et al. (April 2015). "A recent bottleneck of Y chromosome diversity coincides with a global change in culture". Genome Research. 25 (4): 459–466. doi:10.1101/gr.186684.114. PMC 4381518. PMID 25770088.
  2. ^ a b Cruciani, Fulvio; Trombetta, Beniamino; Massaia, Andrea; Destro-Bisol, Giovanni; Sellitto, Daniele; Scozzari, Rosaria (2011). "A Revised Root for the Human y Chromosomal Phylogenetic Tree: The Origin of Patrilineal Diversity in Africa". The American Journal of Human Genetics. 88 (6): 814–818. doi:10.1016/j.ajhg.2011.05.002. PMC 3113241. PMID 21601174.
  3. ^ Ansari Pour, Naser; Plaster, Christopher; Bradman, Neil (2013). "Evidence from Y-chromosome analysis for a late exclusively eastern expansion of the Bantu-speaking people". European Journal of Human Genetics. 21 (4): 423–429. doi:10.1038/ejhg.2012.176. PMC 3598330. PMID 22892538.
  4. ^ Fu, Qiaomei; Posth, Cosimo; Hajdinjak, Mateja; Petr, Martin; Mallick, Swapan; Fernandes, Daniel; Furtwängler, Anja; Haak, Wolfgang; Meyer, Matthias; Mittnik, Alissa; Nickel, Birgit; Peltzer, Alexander; Rohland, Nadin; Slon, Viviane; Talamo, Sahra; Lazaridis, Iosif; Lipson, Mark; Mathieson, Iain; Schiffels, Stephan; Skoglund, Pontus; Derevianko, Anatoly P; Drozdov, Nikolai; Slavinsky, Vyacheslav; Tsybankov, Alexander; Cremonesi, Renata Grifoni; Mallegni, Francesco; Gély, Bernard; Vacca, Eligio; Morales, Manuel R. González; et al. (2016). "The genetic history of Ice Age Europe" (Full text). Nature. 534 (7606): 200–5. doi:10.1038/nature17993. PMC 4943878. PMID 27135931.
  5. ^ Skoglund, Pontus; Thompson, Jessica C; Prendergast, Mary E; Mittnik, Alissa; Sirak, Kendra; Hajdinjak, Mateja; Salie, Tasneem; Rohland, Nadin; Mallick, Swapan; Peltzer, Alexander; Heinze, Anja; Olalde, Iñigo; Ferry, Matthew; Harney, Eadaoin; Michel, Megan; Stewardson, Kristin; Cerezo-Román, Jessica I; Chiumia, Chrissy; Crowther, Alison; Gomani-Chindebvu, Elizabeth; Gidna, Agness O; Grillo, Katherine M; Helenius, I. Taneli; Hellenthal, Garrett; Helm, Richard; Horton, Mark; López, Saioa; Mabulla, Audax Z.P; Parkington, John; et al. (2017). "Reconstructing Prehistoric African Population Structure". Cell. 171 (1): 59–71.e21. doi:10.1016/j.cell.2017.08.049. PMC 5679310. PMID 28938123.
  6. ^ Y-DNA Haplogroup A and its Subclades - 2012 (BT as subclade of A1b-P108) Y-DNA Haplogroup A and its Subclades - 2014 (BT as subclade of A1b-P108); Y-DNA Haplogroup Tree 2015 (BT-M91 listed as subclade of A1a-M31). ISOGG has listed M42 as a mutation characteristic (but not defining) of BT since 2012.
  7. ^ ISOGG Haplogroup A (2012): "BT is shown on this tree, though it is not considered to be a part of Haplogroup A, in order to make it clear that, as a sibling clade of A1b1, BT and all other haplogroups are downstream of A1b. Listed 15 February 2012." (also note that the group labelled "A1b" in the image is the "A0" of ISOGG (2012)).
"Y-chromosomal Adam"
A00 A0-T [χ 3]
A0 A1 [χ 4]
A1a A1b
A1b1 BT
F1  F2  F3  GHIJK
I   J     LT [χ 5]       K2 [χ 6]
L     T    K2a [χ 7]        K2b [χ 8]     K2c     K2d K2e [χ 9]  
K-M2313 [χ 10]     K2b1 [χ 11] P [χ 12]
NO   S [χ 13]  M [χ 14]    P1     P2