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Haplogroup X is a human mitochondrial DNA (mtDNA) haplogroup. It is found in America, Europe, Western Asia, North Africa, and the Horn of Africa.

Haplogroup X
Haplogroup X (mtDNA).PNG
Possible time of originca. 45,000–20,000 years ago[1]
AncestorN
DescendantsX1, X2
Defining mutations73, 7028, 11719, 12705, 14766, 16189, 16223, 16278[2]
mtDNA-based chart of possible large human migrations.

Haplogroup X arose from haplogroup N, roughly 30,000 years ago (just prior to or during the Last Glacial Maximum). It is in turn ancestral to subclades X2 and X1, which arose ca. 20,000 and ca. 12,000 years ago, respectively.[1]

DistributionEdit

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

Overall, haplogroup X is found in around 2% of the population of Europe, the Near East and North Africa. It is especially common, 14.3%, among the natives of Bahariya Oasis (Western Desert, Egypt.[5] The X1 subclade is much less frequent, and is largely restricted to North Africa, the Horn of Africa and the Near East.

Subclade X2 appears to have undergone extensive population expansion and dispersal around or soon after the Last Glacial Maximum, roughly 20,000 years ago. It is more strongly represented in the Near East, the Caucasus, and Southern Europe and somewhat less strongly present in the rest of Europe. The highest concentrations are found in Georgia (8%), Orkney (Scotland) (7%), and amongst the Druze community in Israel (27%). Subclades X2a and X2g are found in North America, but are not present in native South Americans.[6]

ArchaeogeneticsEdit

Haplogroup X has been found in various other fossils that were analysed for ancient DNA, including specimens associated with the Alföld Linear Pottery (X2b-T226C, Garadna-Elkerülő út site 2, 1/1 or 100%), Linearbandkeramik (X2d1, Halberstadt-Sonntagsfeld, 1/22 or ~5%), and Iberia Chalcolithic (X2b, La Chabola de la Hechicera, 1/3 or 33%; X2b, El Sotillo, 1/3 or 33%; X2b, El Mirador Cave, 1/12 or ~8%) cultures.[7] Haplogroup X has been found in ancient Egyptian mummies excavated at the Abusir el-Meleq archaeological site in Middle Egypt, which date from the late New Kingdom and Roman periods.[8] Fossils excavated at the Late Neolithic site of Kelif el Boroud (Kehf el Baroud) in Morocco, which have been dated to around 5,000 years old, have also been found to carry the X2 subclade.[9]

DruzeEdit

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%).[10] 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.[11]

North AmericaEdit

Haplogroup X is also one of the five haplogroups found in the indigenous peoples of the Americas.[12] (namely, X2a subclade).

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.[13][14] 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%).[15]

Unlike the four main Native American mtDNA haplogroups (A, B, C, D), X is not strongly associated with East Asia. The main occurrence of X in Asia discovered so far is in the Altai people in Siberia.[16]

One theory of how the X Haplogroup ended up in North America is that the people carrying it migrated from central Asia along with haplogroups A, B, C, and D, from an ancestor from the Altai Region of Central Asia.[17] Two sequences of haplogroup X2 were sampled further east of Altai among the Evenks of Central Siberia.[10] 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.[17]

This relative absence of haplogroup X2 in Asia is one of the major factors used to support the Solutrean hypothesis during the early 2000s. The Solutrean hypothesis postulates that haplogroup X reached North America with a wave of European migration emerging from the Solutrean culture, roughly 20,000 years ago .[18][19] a stone-age culture in south-western France and in Spain, by boat around the southern edge of the Arctic ice pack. Since the later 2000s and during the 2010s, evidence has turned against the Solutrean hypothesis, as no presence of mt-DNA ancestral to X2a has been found in Europe or the Near East. New World lineages X2a and X2g are not derived form the Old World lineages X2b, X2c, X2d, X2e, and X2f, indicating an early origin of the New World lineages "likely at the very beginning of their expansion and spread from the Near East".[17] A 2008 study came to the conclusion that the presence of haplogroup X in the Americas does not support migration from Solutrean-period Europe.[20] The lineage of haplogroup X in the Americas is not derived from a European subclade, but rather represent an independent subclade, labelled X2a.[21] The X2a subclade has not been found in Eurasia, and has most likely arisen within the early Paleo-Indian population, at roughly 13,000 years ago.[22] A basal variant of X2a was found in the Kennewick Man fossil (ca. 9,000 years ago).[23]

SubcladesEdit

TreeEdit

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[2] and subsequent published research.

  • X
    • X1
      • X1a
        • X1a1
      • X1b
    • X2
      • X2a
        • X2a1
          • X2a1a
          • X2a1b
        • X2a2
      • X2b
        • X2b1
        • X2b2
        • X2b3
        • X2b4
      • X2c
        • X2c1
        • X2c2
      • X2d
      • X2e
        • X2e1
          • X2e1a
            • X2e1a1
              • X2e1a1a
        • X2e2
          • X2e2a
      • X2f
      • X2g
      • X2h

See alsoEdit

ReferencesEdit

  1. ^ a b X is estimated at 31.8+12.8
    −12.1
     kya
    (95% CI) in: "Correcting for Purifying Selection: An Improved Human Mitochondrial Molecular Clock Supplementary material (p. 87)" (PDF). 2009: 89. Archived from the original (PDF) on 29 December 2009. Cite journal requires |journal= (help)
  2. ^ a b 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.
  3. ^ Bryan Sykes (2001). The Seven Daughters of Eve. London; New York: Bantam Press. ISBN 978-0393020182.
  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. ^ Martina Kujanova; Luisa Pereira; Veronica Fernandes; Joana B. Pereira; Viktor Cerny (2009). "Near Eastern Neolithic Genetic Input in a Small Oasis of the Egyptian Western Desert". American Journal of Physical Anthropology. 140 (2): 336–346. doi:10.1002/ajpa.21078. PMID 19425100.
  6. ^ Perego UA (2009). "Distinctive Paleo-Indian Migration Routes from Beringia Marked by Two Rare mtDNA Haplogroups". Current Biology. 19 (1): 1–8. doi:10.1016/j.cub.2008.11.058. PMID 19135370.
  7. ^ Mark Lipson; et al. (2017). "Parallel palaeogenomic transects reveal complex genetic history of early European farmers". Nature. Retrieved 16 November 2017.
  8. ^ Schuenemann, Verena J.; et al. (2017). "Ancient Egyptian mummy genomes suggest an increase of Sub-Saharan African ancestry in post-Roman periods". Nature Communications. 8: 15694. doi:10.1038/ncomms15694. PMC 5459999. PMID 28556824.
  9. ^ Fregel; et al. (2018). "Ancient genomes from North Africa evidence prehistoric migrations to the Maghreb from both the Levant and Europe". bioRxiv 191569.
  10. ^ a b 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.
  11. ^ Shlush LI, Behar DM, Yudkovsky G, et al. (2008). "The Druze: a population genetic refugium of the Near East". PLoS ONE. 3 (5): e2105. doi:10.1371/journal.pone.0002105. PMC 2324201. PMID 18461126.
  12. ^ "Dolan DNA Learning Center – Native American haplogroups: European lineage, Douglas Wallace". Dnalc.org. Retrieved 28 January 2011.
  13. ^ "The peopling of the Americas: Genetic ancestry influences health". Scientific American.
  14. ^ "Learn about Y-DNA Haplogroup Q". Wendy Tymchuk – Senior Technical Editor. Genebase Systems. 2008. Archived from the original (Verbal tutorial possible) on 22 June 2010. Retrieved 21 November 2009.
  15. ^ 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)
  16. ^ 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.
  17. ^ a b c 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. 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.
  18. ^ "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
  19. ^ Carey, Bjorn (19 February 2006)."First Americans may have been European.Life Science. Retrieved on 10 August 2007.
  20. ^ "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." (Fagundes et al. 2008)
  21. ^ "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. 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.
  22. ^ X2a is dated 12.8+7.1
    −6.7
     kya
    in Soares et al. (2009).
  23. ^ "X2a has not been found anywhere in Eurasia, and phylogeography gives us no compelling reason to think it is more likely to come from Europe than from Siberia. Furthermore, analysis of the complete genome of Kennewick Man, who belongs to the most basal lineage of X2a yet identified, gives no indication of recent European ancestry and moves the location of the deepest branch of X2a to the West Coast, consistent with X2a belonging to the same ancestral population as the other founder mitochondrial haplogroups. Nor have any high-resolution studies of genome-wide data from Native American populations yielded any evidence of Pleistocene European ancestry or trans-Atlantic gene flow." Raff, Jennifer A.; Bolnick, Deborah A (2015). "Does Mitochondrial Haplogroup X Indicate Ancient Trans-Atlantic Migration to the Americas? A Critical Re-Evaluation". PaleoAmerica: A Journal of Early Human Migration and Dispersal. 1 (4): 297–304. doi:10.1179/2055556315Z.00000000040.

External linksEdit

Further readingEdit