Haplogroup G (Y-DNA)



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 or Southern Asia, likely in the region that is now northern India, Pakistan, and Afghanistan. The haplogroup began to spread with the Neolithic Agricultural Revolution, perhaps with the appearance of the early horse nomads of the Eurasian steppe.

Distribution
Haplogroup G has an overall low frequency in most populations but is widely distributed within the Old World in Europe, Western Asia, northeastern Africa, Central Asia, South Asia, and Southeast Asia (including parts of China and the Malay Archipelago). 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 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 Southern Asia, haplogroup G is found at a rate of 10% to 20% among Iranians, Pashtuns (ethnic Afghans), and Kalash, and at a lesser percentage among some other populations in Pakistan, India, and Sri Lanka, 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 the northwest of the Indian subcontinent at the start of the first millennium. 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), G2a (P15) and G2c (M377). G3 (P287) exists but is rarely found in the G population. The highest reported concentration of G1 is in Iran, with next most frequent concentrations in neighboring countries. G2 represents the majority of haplogroup G Y-chromosomes in all countries, and a recently discovered subcategory (likely to be called G2a3) accounts for a high percentage of G in all sampled countries.

A clade of closely related Ashkenazi Jews represent virtually all G2c persons, with just three other G2c haplotypes having been reported so far: one Turk from Kars in northeast Turkey near Armenia, one Pashtun, and one Burusho in Pakistan. The extreme rarity of G2c in northeast Pakistan could indicate that G2c 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 Greco-Bactrian Kingdom). These two reported Pakistani G2c haplotypes are quite divergent from the Ashkenazi Jewish clade, and therefore do not at all indicate a recent common origin. The Turkish G2c is somewhat closer, but not identical. It remains to be seen if testing will reveal G2c haplotypes in other populations — this is some indication that G2c occurs at low levels in the Near East. Early reports that Ashkenazi G men 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 G2c men. All G2c men 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 most other G haplotypes. 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 men worldwide.

Phylogeny
This is a synthesis of the data about the internal phylogeny of haplogroup G from the latest upcoming studies:

(Temporarily embargoed till publication)