Haplogroup X (mtDNA)

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Haplogroup X
Haplogroup X (mtDNA).PNG
Possible time of origin 30,000 YBP
Ancestor N
Descendants X1, X2
Defining mutations 73, 7028, 11719, 12705, 14766, 16189, 16223, 16278[1]

In human mitochondrial genetics, Haplogroup X is a human mitochondrial DNA (mtDNA) haplogroup found in Native Americans, Europeans, and Western Asians.


File:Peopling of eurasia.jpg
mtDNA-based chart of possible large human migrations.

The genetic sequences of haplogroup X diverged originally from haplogroup N, and subsequently further diverged about 30,000 years ago[2] to give two sub-groups, X1 and X2.


Haplogroup X is found in approximately 7% of native Europeans,[3] and 3% of all Native Americans from North America.[4]

Overall haplogroup X accounts for about 2% of the population of Europe, the Near East, and North Africa.

Sub-group X1 is much less numerous, and is largely restricted to North and East Africa, and also the Near East.

Sub-group X2 appears to have undergone extensive population expansion and dispersal around or soon after the last glacial maximum, about 21,000 years ago. It is more strongly present in the Near East, the Caucasus, and Mediterranean Europe; and somewhat less strongly present in the rest of Europe. Particular concentrations appear in Georgia (8%), the Orkney Islands (in Scotland) (7%), and amongst the Israeli Druze community (27%). Subclades X2a and X2g are found in North America, but are not present in native South Americans.[5]


The greatest frequency of haplogroup X is observed in the Druze, a minority population in Israel, Jordan, Lebanon, and Syria, as much in X1 (16%) as in X2 (11%).[6] The Druze also have much diversity of X lineages. This pattern of heterogeneous parental origins is consistent with Druze oral tradition. The Galilee Druze represent a population isolate, so their combination of a high frequency and diversity of X signifies a phylogenetic refugium, providing a sample snapshot of the genetic landscape of the Near East prior to the modern age.[7]

North America

Haplogroup X is also one of the five haplogroups found in the indigenous peoples of the Americas.[8] Although it occurs only at a frequency of about 3% for the total current indigenous population of the Americas, it is a bigger haplogroup in northern North America, where among the Algonquian peoples it comprises up to 25% of mtDNA types.[9][10] It is also present in lesser percentages to the west and south of this area—among the Sioux (15%), the Nuu-Chah-Nulth (11%–13%), the Navajo (7%), and the Yakama (5%).[11]

Unlike the four main Native American mtDNA haplogroups (A, B, C, D), X is not at all strongly associated with East Asia. The main occurrence of X in Asia discovered so far is in the Altay people in Siberia,[12] and detailed examination[6] has shown that the Altaian sequences are all almost identical (haplogroup X2e), suggesting that they arrived in the area probably from the South Caucasus more recently than 5,000 BP. In addition, Zegura et al. 2003 ascertained that only the Altai and southwest Siberian regions "possesses all of the major Native American Y chromosome" and that "mtDNA founding haplogroups, thereby making it the best available candidate for the ancestral source region for the Native American population system."[13]

Earlier (2001) research indicated that Altaians have maintained their native identity and only begun, very recently, to mix with groups (mostly Russians and Kazakhs) who do not show mtDNA haplogroup X. Genetic studies and researchers show, "the analysis of the tribal structure of Southern Altaians has shown that the present-day Altaians have retained their native language and ethnic identity. They have begun to mix with other ethnic groups (mostly Russians and Kazakhs) only recently, so the interethnic admixture is estimated to be <5% (Luzina 1987; Osipova et al. 1997). The haplogroup X mtDNAs have not been found in populations of central Asia, including Kazakhs, Uighurs, and Kirghizs (Comas et al. 1998). Since the frequency of haplogroup X in Russians is extremely low (3 of 336; Orekhov et al. 1999; Malyarchuk and Derenko 2000; authors’ unpublished data), the recent European admixture cannot explain the presence of haplogroup X in the Altaians. Hence, the results of the present study allow us to suggest that haplogroup X was the part of the ancestral gene pool for Altaian populations, being found both in northern and southern Altaians."[12]

In addition, these same (2001) researchers indicated that the mtDNA haplogroup X haplotype present in the Altaians of Siberia is intermediate between Native Americans clades and that of Europeans. As a Russian research group observed, "American Indian and European haplogroup X mtDNAs ... are distantly related to each other". They propose however not an early European colonization of America, but that Altaians contributed to migrants bound for Europe and America; "The network further suggests that the Altaian X haplotypes occupy the intermediate position between European and American Indian haplogroup X mtDNA lineages"[12] However, further research in 2003 indicated that the haplotype present in the Altaians is not intermediate between Native American clades and that of Europeans, and that the Native Americans probably split early from the others, with the split occurring "likely at the very beginning of their expansion and spread from the Near East, ... around, or after, the Last Glacial Maximum when the climate ameliorated".[6]

One theory of how the X Haplogroup ended up in North America is it migrated from central Asia along with the A, B, C, and D Haplogroups, from an ancestor from the Altai Region of Central Asia.[14] Two sequences of haplogroup X2 were sampled further east of Altai among the Evenks of Central Siberia.[6] These two sequences belong to X2* and X2b. It is uncertain if they represent a remnant of the migration of X2 through Siberia or a more recent input.[14]

This relative absence of haplogroup X2 in Asia is one of the major factors used to support the Solutrean hypothesis. However, the New World haplogroup X2a is as different from any of the Old World X2b, X2c, X2d, X2e, and X2f lineages as they are from each other, indicating an early origin "likely at the very beginning of their expansion and spread from the Near East".[14]

The Solutrean hypothesis postulates that haplogroup X reached North America with a wave of European migration about 20,000 BP by the Solutreans,[15][16] a stone-age culture in south-western France and in Spain, by boat around the southern edge of the Arctic ice pack.

In a 2008 article in the American Journal of Human Genetics, a group of researchers in Brazil (except for David Glenn Smith, of U.C. Davis) argue against the Solutrean hypothesis, stating: "Our results strongly support the hypothesis that haplogroup X, together with the other four main mtDNA haplogroups, was part of the gene pool of a single Native American founding population; therefore they do not support models that propose haplogroup-independent migrations, such as the migration from Europe posed by the Solutrean hypothesis ... Here we show, by using 86 complete mitochondrial genomes, that all Native American haplogroups, including haplogroup X, were part of a single founding population, thereby refuting multiple-migration models." [11]

An abstract in a 2012 issue of the "American Journal of Physical Anthropology" states that "The similarities in ages and geographical distributions for C4c and the previously analyzed X2a lineage provide support to the scenario of a dual origin for Paleo-Indians. Taking into account that C4c is deeply rooted in the Asian portion of the mtDNA phylogeny and is indubitably of Asian origin, the finding that C4c and X2a are characterized by parallel genetic histories definitively dismisses the controversial hypothesis of an Atlantic glacial entry route into North America."[17]



This phylogenetic tree of haplogroup X subclades is based on the paper by Mannis van Oven and Manfred Kayser Updated comprehensive phylogenetic tree of global human mitochondrial DNA variation[1] and subsequent published research.

  • X
    • X1
      • X1a
        • X1a1
      • X1b
    • X2
      • X2a
        • X2a1
          • X2a1a
          • X2a1b
        • X2a2
      • X2b
        • X2b1
        • X2b2
        • X2b3
        • X2b4
      • X2c
        • X2c1
      • X2d
      • X2e
        • X2e1
          • X2e1a
            • X2e1a1
              • X2e1a1a
        • X2e2
          • X2e2a
      • X2f
      • X2g
      • X2h

Popular culture

In his popular book The Seven Daughters of Eve, Bryan Sykes named the originator of the European-American subset of this mtDNA haplogroup - corresponding to X2 - "Xenia".

See also

Evolutionary tree of human mitochondrial DNA (mtDNA) haplogroups

  Mitochondrial Eve (L)    
L0 L1–6
L1 L2 L3   L4 L5 L6
  M   N  
CZ D E G Q   O A S   R   I W X Y
C Z B F R0   pre-JT P  U

External links


  1. 1.0 1.1 van Oven M, Kayser M (February 2009). "Updated comprehensive phylogenetic tree of global human mitochondrial DNA variation". Human Mutation. 30 (2): E386-94. doi:10.1002/humu.20921. PMID 18853457.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  2. Soares, Pedro et al 2009, Correcting for Purifying Selection: An Improved Human Mitochondrial Molecular Clock. and its Supplemental Data. The American Journal of Human Genetics, Volume 84, Issue 6, 740-759, 4 June 2009
  3. Bryan Sykes (2001). The Seven Daughters of Eve. London; New York: Bantam Press. ISBN 0393020185.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  4. Malhi and Smith, Brief Communication: Haplogroup X Confirmed in Prehistoric North America, American Journal of Physical Anthropology, Volume 119, Issue 1, (September 2002), Pages 84-86.
  5. U. Perego et al., Distinctive Paleo-Indian Migration Routes from Beringia Marked by Two Rare mtDNA Haplogroups, Current Biology, Volume 19, Issue 1, (13 January 2009), Pages 1-8.
  6. 6.0 6.1 6.2 6.3 Reidla M, Kivisild T, Metspalu E, Kaldma K, Tambets K, Tolk HV, et al. (November 2003). "Origin and diffusion of mtDNA haplogroup X". American Journal of Human Genetics. 73 (5): 1178–90. doi:10.1086/379380. PMC 1180497. PMID 14574647.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  7. L.I. Shlush, D.M. Behar et al., The Druze: A Population Genetic Refugium of the Near East, PLoS ONE, vol. 3, no. 5 (2008), e2105.
  8. "Dolan DNA Learning Center – Native American haplogroups: European lineage, Douglas Wallace". Dnalc.org. Retrieved 28 January 2011.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  9. "The peopling of the Americas: Genetic ancestry influences health". Scientific American.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  10. "Learn about Y-DNA Haplogroup Q" (Verbal tutorial possible). Wendy Tymchuk – Senior Technical Editor. Genebase Systems. 2008. Retrieved 21 November 2009.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  11. 11.0 11.1 Fagundes NJ, Kanitz R, Eckert R, Valls AC, Bogo MR, Salzano FM, Smith DG, Silva WA, Zago MA, Ribeiro-dos-Santos AK, Santos SE, Petzl-Erler ML, Bonatto SL (March 2008). "Mitochondrial population genomics supports a single pre-Clovis origin with a coastal route for the peopling of the Americas". American Journal of Human Genetics. 82 (3): 583–92. doi:10.1016/j.ajhg.2007.11.013. PMC 2427228. PMID 18313026. (Click here for PDF Format)<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  12. 12.0 12.1 12.2 12.3 Derenko MV, Grzybowski T, Malyarchuk BA, Czarny J, Miścicka-Sliwka D, Zakharov IA (July 2001). "The presence of mitochondrial haplogroup x in Altaians from South Siberia". American Journal of Human Genetics. 69 (1): 237–41. doi:10.1086/321266. PMC 1226041. PMID 11410843.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  13. Stephen L. Zegura, Tatiana M. Karafet, Lev A. Zhivotovsky. and Michael F. Hammer. "High-Resolution SNPs and Microsatellite Haplotypes Point to a Single, Recent Entry of Native American Y Chromosomes into the Americas". Mol Biol Evol (2004) 21 (1): 164-175. doi: 10.1093/molbev/msh009 First published online: October 31, 2003. http://mbe.oxfordjournals.org/content/21/1/164.full
  14. 14.0 14.1 14.2 Reidla M, Kivisild T, Metspalu E, Kaldma K, Tambets K, Tolk HV, et al. (November 2003). "Origin and diffusion of mtDNA haplogroup X". American Journal of Human Genetics. The American Society of Human Genetics. 73 (5): 1178–90. doi:10.1086/379380. PMC 1180497. PMID 14574647. It is apparent that the Native American haplogroup X mtDNAs derive from X2 by a unique combination of five mutations. It is notable that X2 includes the two complete Native American X sequences that constitute the distinctive X2a clade, a clade that lacks close relatives in the entire Old World, including Siberia. The position of X2a in the phylogenetic tree suggests an early split from the other X2 clades, likely at the very beginning of their expansion and spread from the Near East northeast of the Altai area, haplogroup X sequences were detected in the Tungusic-speaking Evenks, of the Podkamennaya Tunguska basin (Central Siberia). In contrast to the Altaians, the Evenks did not harbor any West Eurasian mtDNA haplogroups other than X. However, neither of the two Evenk X haplotypes showed mutations characteristic of the Native American clade X2a. Instead, one sequence was a member of X2b and the other of X2. Thus, one possible scenario is that several X haplotypes arrived in Siberia from western Asia during the Palaeolithic, but only X2a crossed Beringia and survived in modern Native Americans.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  15. The North Atlantic ice-edge corridor: a possible Palaeolithic route to the New World. Bruce Bradley and Dennis Stanford. World Archaeology 2004 Vol. 36(4):459–478. http://planet.uwc.ac.za/nisl/Conservation%20Biology/Karen%20PDF/Clovis/Bradley%20&%20Stanford%202004.pdf
  16. Carey, Bjorn (19 February 2006).First Americans may have been European.Life Science. Retrieved on 10 August 2007.
  17. Hooshiar Kashani B, Perego UA, Olivieri A, Angerhofer N, Gandini F, Carossa V, Lancioni H, Semino O, Woodward SR, Achilli A, Torroni A (January 2012). "Mitochondrial haplogroup C4c: a rare lineage entering America through the ice-free corridor?". American Journal of Physical Anthropology. 147 (1): 35–9. doi:10.1002/ajpa.21614. PMID 22024980.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>

Further reading