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Haplogroup J2 (Y-DNA)
In human genetics, Haplogroup J2 (M172) is a Y-chromosome haplogroup which is a subdivision of haplogroup J. It is further divided into two complementary clades, J2a-M410 and J2b-M12[1].
OriginsHaplogroup J2 is widely believed to be associated with the spread of agriculture from the northern Fertile Crescent, the Levant, and Anatolia [2],[3]. The age of J2 has been estimated as 18,500 +/- 3,500 thousand years ago[3]. Its distribution, centered in West Asia and Southeastern Europe, its association with the presence of Neolithic archaeological artifacts, such as figurines and painted pottery [4], and its association with annual precipitation have been interpreted as evidence that J2, and in particular its J2a-M410 subclade belonged to the agricultural innovators who followed the rainfall[5]. Distribution
subclades of J2 Haplogroup Another important fact about the distribution of Haplogroup J2 is that it appears to have dispersed from a Middle Eastern homeland to the west through a primarily maritime or littoral route, as it is found in high concentrations among the populations of the coasts of the Mediterranean Sea in both Eurasia and Africa, and particularly along the coasts of the eastern Mediterranean in Europe. This distribution may be more consonant with a Neolithic or post-Neolithic maritime dispersal from the Middle East, such as through Greek colonization[8] or even Phoenician commercial and colonial activities. In Italy, J2 is found in about 23% of southern Italians, and 17% of central-north Italians[9]. Turkey is one of the countries with major J2 population. 24% of Turkish men are J2 according to a recent study[2], with regional frequencies ranging between 10% and 31%. Combined with J1, one third of the total population of Turkish people belongs to Haplogroup J. In neighboring Greece, as in Italy J2 is also common, with regional frequencies ranging between 11% and 46%. It has been proposed that haplogroup J2a-M410 was linked to populations on ancient Crete by examining the relationship between Anatolian, Cretan, and Greek populations from around early Neolithic sites[10]. Haplogroup J2b-M12 was associated with Neolithic Greece (ca. 8500 - 4300 BCE) and was reported to be found in modern Crete (3.1%) and mainland Greece (Macedonia 7.0%, Thessaly 8.8%, Argolis 1.8%) [11]. Sephardic Jews have about 29% of haplogroup J2[3] and Ashkenazi Jews have 23%[3], or 19%[12]. It has been reported that a sample of Italian Cohens belong to Network 1.2, a group of Y chromosomes characterized by a value of the DYS413 marker less or equal to 18. This deletion has been placed in the J2a-M410 clade[1][11]. However, other Jewish Cohens belong to haplogroup J1 (see Cohen modal haplotype). J2 subclades are also found in the South Caucasus (Georgia, Armenia, Azerbaijan), Iran, Central Asia, and South Asia. Typically, modern populations of the southern Middle East (especially Arabic-speaking ones) have a higher frequency of the related haplogroup J1, whereas the great majority of Haplogroup J representatives among the populations of the Northern Middle East, Europe, and India belong to the subclade J2. Haplogroup J2 has been shown to have a more northerly distribution in the Middle East, although it exists in significant amounts in the southern middle-east regions, a lesser amount of it was found when compared to its brother haplogroup, J1, which has a more southerly distribution. This suggests that, if the occurrence of Haplogroup J among modern populations of Europe, Central Asia, and South Asia does reflect Neolithic demic diffusion from the Middle East, the source population is more likely to have originated from Anatolia, the Levant or northern Mesopotamia than from regions further south. Haplogroup J2a-M410 in India is largely confined to the upper castes[1] with little occurrence in the middle and lower castes and is completely absent from south Indian tribes and middle and lower castes. SubdivisionsHaplogroup J2 is subdivided into two complementary sub-haplogroups: J2a, defined by the M410 genetic marker, and J2b, defined by the M12 genetic marker. A subclade of haplogroup J2a, defined by the M92 marker has been implicated in the ancient Greek colonization [8]. The subclades of Haplogroup J2 with their defining mutation, according to the 2006 ISOGG tree:
J2 (M-172) is divided into eight sub-Haplogroups defined by mutations M12/M102, M47, M67/M92, M68, M137, M158, M339, and M340 (see Diagram), four of which occur at informative frequencies[3]. The less-heterogeneous J2 (J-M172), which occurs as frequently as J1 (J-M267) in some Middle Eastern populations, is the more prevalent in Europe. J-M102 illustrates population expansions from the southern Balkans. J-M67 is most frequent in the Caucasus (especially Armenia and Georgia), and J-M92, which indicates affinity between Anatolia and southern Italy. Whereas J-M67* and J-M92 show higher frequencies and variances in Europe and in Turkey. Likewise, J-M47 and J-M68 characterize very few Near Eastern and Asian samples[3]. ReferencesBibliography
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