| HAPLOGROUP X (MTDNA)
Haplogroup X Possible
time of origin ca. : 45,000–20,000 years ago
Haplogroup X is a human mitochondrial DNA (mtDNA) haplogroup. It is found in America, Europe, Western Asia, North Africa, and the Horn of Africa.
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.
Distribution
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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. 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.
Archaeogenetics
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Druze
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North
America :
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. 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%).
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.
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. Two sequences of haplogroup X2 were sampled further east of Altai among the Evenks of Central Siberia. 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.
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. 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". A 2008 study came to the conclusion that the presence of haplogroup X in the Americas does not support migration from Solutrean-period Europe. The lineage of haplogroup X in the Americas is not derived from a European subclade, but rather represent an independent subclade, labelled X2a. 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. A basal variant of X2a was found in the Kennewick Man fossil (ca. 9,000 years ago).
Subclades
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Haplogroup X diverged from Haplogroup N more than 30,000ybp. It further split more than 20,000ybp into 2 main subgroups, X1 and X2. Haplogroup X is found in Europe, the Near East, Central Asia, North Africa and North America, and is believed to have migrated to the Americas about 15,000 years ago, making up a very small component of the Native American population (less than 3%). Bryan Sykes in his book named this mtDNA haplogroup Xenia.
Haplogroup X subclade X1 appears to be largely restricted to North Africa, East Africa and the Near East. It is characterized by an HVR2 mutation at 146. Haplogroup X1 is further divided into X1a and X1b.
Subclade X2 is more widely distributed throughout Mediterranean Europe, the Caucasus, the Near East and North America. Haplogroup X2 is divided into further subgroups. X2a is found in a few geographically diverse Native American populations, such as Navajo, Yakima and Ojibwa. It is characterized by a HVR mutations at 200 and 16213. Recent work has identified 2 sub branches of X2a. X2a1 in the Great Lakes area, and X2a2 in the west. Another Native American subgroup X2g has been identified as separate from X2a. X2b is the most geographically diverse, covering Europe and the Near East. It is characterized by an HVR2 mutation at 226. Recently an X2b1 subclade has been identified in a group of Moroccans. X2c is characterized by an HVR1 mutation at 255. X2d and X2e are characterized by mutations in the coding region that can not be differentiated from other X2's without additional mtDNA testing beyond HVR1 and HVR2. X2f is characterized by a HVR2 mutation at 257.
This Motif table is used to estimate the subclades for Haplogroup X. Exact identification requires markers in the mtDNA coding region not covered by standard mtDNA HVR1 and HVR2 testing.
One theory of how the X Haplogroup ended up in North America is they migrated from central Asia along with the A,B,C, and D Haplogroups. It is interesting that no Haplogroup X traces have been found in Siberia. The nearest X Haplotypes have been found is the Altai region of central Asia. This theory is supported by yDNA studies [Zegura.]
Schurr postulates that Haplogroup X arrived in North America via the central corridor which became free of ice about 12500 ybp.
Another theory, The Solutrean Hypothesis, is that the there was a early pre-Clovis Atlantic migration route in addition to the Asian Bering Straight land bridge as shown on the following map :
Other more imaginitive theories include :
The Mormon hypothesis, which states the Haplogroup X in North American could be the result of descendants of Lehi and Sariah as mentioned in the Book of Mormon.
The Neanderthal Hypothesis. That Haplogroup X mtDNA is descended from the Homo Sapiens Neanderthalis. While there are some X motif markers present in some Neanderthal mtDNA samples, there are also many more differences.
And finally, the Atlantis hypothesis, Where Haplogroup X is identified with the remenants of the Atlantean civilization.
Source :
https://en.wikipedia.org/ https://www.familytreedna.com/ |
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