Haplogroup G (Y-DNA)

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In human genetics, Haplogroup G (M201) is a Y-chromosome haplogroup. It is a branch of Haplogroup F (M89), and is theorized to have originated, according to the latest thinking, in the Near East, and began to spread with the Neolithic Agricultural Revolution, perhaps with the appearance of the early horse nomads of the Eurasian steppe.

Haplogroup G has an overall low frequency in most populations but is widely distributed within the Old World in Europe, western Asia, the Middle East, northeastern Africa, Central Asia, South Asia, and Southeast Asia (including parts of China). It is most frequent in the Caucasus (found at over 60% in ethnic North Ossetian males and ~30% in Georgian males). In Europe, haplogroup G is found at ~5% in central and southern sections of the continent. It has relatively high concentrations in the Catalan-speaking region of northern Sardinia (over 25%) and the Tyrol region of Austria (about ~15%). In the British Isles, Scandinavia, and the Baltic countries it is uncommon; Britain and Norway for example at 1-2%.

In South Asia, haplogroup G2 is found at a rate of about 10% in Pakistan, and at a lesser percentage among some populations in India, including the Tamils. In Central Asia, G is found in small percentages in a belt extending from the Caucasus through the Central Asian steppes out to the Uyghurs of Xinjiang Province in western China.

The initial distribution of haplogroup G in Europe may reflect a migration of agriculture-bringing Anatolian people into the Mediterranean Basin. The haplogroup may also have been brought by invading Sarmatians, Alans and Jasz (all descendant groups of the 'Iranian' Scythians), which is a good fit with the historically attested spread of these peoples across the Central Asian steppe, from Xinjiang in the east to Iberia and Tunisia in the west, with a branch (the Sakas) entering nortwest Indian sub-Continent at the start of the first millenium. Around 10% of Ashkenazi Jewish males have haplogroup G, and the Jewish diaspora to Europe from the Middle East and the Arab Moor occupation of Spain are two other probable routes into Europe for certain types of G.

Three commonly occurring subgroups of Haplogroup G have been identified so far: G1 (M285), G2 (P15) and G5 (M377). Mutations distinguishing G3 and G4 exist but are rarely found in the G population. The highest reported concentration of G1 is in Iran, with next most frequent concentrations in neighboring countries. G2 contains the majority of haplogroup G Y-chromosomes in all countries, and a recently discovered subcategory (likely to be called G2c) accounts for a high percentage of G in all sampled countries.

A clade of closely related Ashkenazi Jews represent virtually all G5 persons, with just two other G5 haplotypes having been reported so far, one Pathan, and one Burusho in Pakistan. The extreme rarity of G5 in northeast Pakistan could indicate that G5 in this area originates outside the region and was brought there in the historic period, perhaps from further west (this area was part of both the Achaemenid Persian Empire, conquered by Alexander the Great, and then formed a part of the Graeco-Bactrian Kingdom). These two reported G5 haplotypes are quite divergent from the Ashkenazi Jewish clade, and therefore do not at all indicate a recent common origin. It remains to be seen if testing will reveal G5 haplotypes in other populations - this is some indication that G5 occurs at low levels in the Near East. Early reports that Ashkenazi G persons were all G1 are now proven incorrect. There are also Jewish genetic clades within G2 and G1 whose members are not closely related to the G5 persons. All G5 persons tested so far have a rare null value for the DYS425 marker, (a missing "T" allele of the DYS371 palindromic STR), the result of a RecLOH event, a finding not yet seen among other G haplotypes. Those G2 persons most closely related to G5 Jews have an unusual incidence of crypto-Judaism in their family histories. Among Jews worldwide, haplogroup G comprises between 10% - 20% of the population. Though forming some recognizable clades, Jews today comprise a small percentage of the total number of G persons worldwide.

[edit] References

- Haplogroup G SNP project
- Some Information and Theories on Haplogroup G
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