Haplogroup R1a

Haplogroup R1a (R1a) is the name given to a major human Y-chromosome haplogroup within R1 (R-M173). In other words, it is one of the major male-lines of all humanity.

It is found at high frequencies in a wide geographic area extending from South Asia to Central and Eastern Europe and Southern Siberia.^[1]

R1a is believed to have originated somewhere within this same area in Eurasia, most likely in the area from Eastern Europe to South Asia. Major reviews of data published in 2009 have lead to a slight preference towards Asia rather than Europe, as will be discussed in detail below.

R1a has a relatively close common ancestry with several other major R haplogroup branches, most notably, R1b, the most common male lineage of Western Europe, and R2, found in South Asia.

Subclades

The phylogenetic ("family tree") naming system commonly used for this haplogroup remains inconsistent in different published sources. Although it has not yet used much in published surveys, a fuller survey of known mutations is listed by ISOGG, and also given in Underhill et al. (2009).^[2]

Prior to 2009 the mutation SRY1532.2 (or SRY10831.2) defined R1a. However R1a* existed which did not have this mutation but had other defining mutations of basal R1a, M420, M449, M511 and M513 (and/or L62 and L63). Henceforth SRY1532.2 variant clade was moved R1a1 and those mutants that define R1a1 were moved into R1a1a. Underhill et al. (2009) also defines the nascent R1a1 clade with M448, M459, and M516, SNPs. The pre-2009 R1a1 clade which was defined by M17 and M198 with the new name R1a1a had been furhter populated with 5 new SNPs: M417, M512, M514, M515, Page07. This renaming is not universally used and the old and new clades are compared on the right.

With the old nomenclature, the most common clade R1a* with the new nomenclature is now broken down into two rare groups of mutations: R1a*, and R1a1* together representing ~1% of all R1a typed Y chromosomes. The most common clade of R1a is therefore R1a1, and the most common clade of R1a1 is R1a1a. Sharma et al. (2009) found 22.8% R1a*, out of 57 people tested from the Saharia tribe of Madhya Pradesh. Other examples include Northern Iran (1 case out of 33 tests), Crete (1 case of R1a(xM198) out of 193 tests), and Greek Macedonia.^[3][4][5]

Distribution

R1a has been found in high frequency at both the eastern and western ends of its core range, for example in some parts of India and Tajikistan on the one hand, and Poland on the other.

Central and Northern Asia

R1a frequencies vary widely between populations within central and northern parts of Eurasia, but R1a is found in areas including Western China and Eastern Siberia. This big variation is possibly a consequence of population bottlenecks in isolated areas and/or the large movements of Turco-Mongols during the historic period. For example, exceptionally high frequencies of R1a1 (R-M17 or R-M198; 50 to 70%) are found among the Ishkashimis, Khojant Tajiks, Kyrgyzs, and in several peoples of Russia's Altai Republic.^[6][7][8] Although levels are comparatively low amongst some Turkic-speaking groups (e.g. Turks, Azeris, Kazakhs, Yakuts), levels are very high in certain Turkic- or Mongolic-speaking groups of Northwestern China, such as the Bonan, Dongxiang, Salar, and Uyghurs.^[6][9][10] R1a lines propogated north-eastward and are scattered amoung certain indigenous Eastern Siberians, including:Kamchatkans and Chukotkans, and peaking in Itel'man at 22%.^[11]

South Asia

In South Asia high levels have been observed in some populations. For example, in the eastern and northern parts of India, among the high caste Bengalis from West Bengal like Brahmins and Kshatriyas (72%), Uttar Pradesh Brahmins (67%), Bihar Brahmins (60%), Punjab (47%), and Gujarat (33%) of male lineages^[12] have been observed in this lineage. It is also found in relatively high frequencies in several South Indian Dravidian-speaking tribes including the Chenchu and Valmikis of Andhra Pradesh and the Kallar of Tamil Nadu suggesting that M17 is widespread in tribal southern Indians^[13].

South-West Asia

The M17 marker is found in five to ten percent of Middle Eastern men. This is true even in western Iranian populations where Persian, a major Indo-European language with close relatives in high frequency areas in Central and South Asia, is spoken. However, on the Eastern side of Iran, around 35% of men carry the M17 maker.^[14] Wells et al. (2001) suggest that the deserts of central Iran acted as "significant barriers to gene flow," and propose two possibilities. First, that the Mesopotamian civilization was densely population relative to immigrating Indo-Iranians; and second, Indo-Iranian languages may have become the predominant language of all Steppe nomads of various ethnic origins. Regueiro et al. (2006), in a study of Iran, noted much higher frequencies in the south than the north and suggested "the lineage may have had an influence on the populations south of the Iranian deserts and where the Dash-e Lut desert would have played a significant role in preventing the expansion of this marker to the north of Iran". The authors suggested that R1a must have originally arrived there prior to any Kurgan/Indo-European expansion into the area, and that the R haplogroup as a whole including R1a may even have roots near Iran.

Europe

In Europe, R1a is found at highest levels among peoples of Eastern European descent (Sorbs, Poles, Russians and Ukranians; 50 to 65%).^[15][16][17] Levels in Hungarians have been noted between 20 and 60% ^[18] The Balkans shows lower frequencies, and significant variation between areas, for example >30% in Slovenia, Croatia and Greek Macedonia, but <10% in Albania, Kosovo and parts of Greece.^[17][19][20]. R1a was present in Europe at least 4600 years ago, as demonstrated by Y-DNA extracted from the remains of three individuals near Eulau, Saxony-Anhalt, Germany, discovered in 2005. The discovery demonstrated the appearance of R1a with Corded Ware culture in Central Europe.^[21][22]

There is a significant presence in peoples of Scandinavian descent.^[23] In Iceland, for instance, R1a accounts for nearly a quarter of the local male Y-DNA. Vikings and Normans may have carried the R1a lineage westward; accounting for a small presence in the British Isles.^{[24][25][26][27]}

In Southern Europe R1a is not normally common but it is widespread and found in significant pockets. Scozzari et al. (2001) found significant levels in the Pas Valley in Northern Spain, and also the areas of Venice, and Calabria in Italy.

Origins

As of November 2009 R1a is defined by the following mutations: L62?, L63?, M420, M449, M511, M513.

The exact point of origin of R1a's dispersal pattern found today remains the subject of discussion. It presumably originated somewhere in the Eurasian landmass, where it is most commonly found today. There is a broad discussion of the possible origin of the largest subclade within R1a*/R1a1* tiers, R1a1a. Establishing the origin of this haplogroup maybe considerably easier than establishing the place of origin of R1a* since R1a* is relatively scarce.

Because R1a* and R1a1* are spread at low frequencies across a broad area, it is difficult to pinpoint sites of diversity, while many studies point toward R1a1a diversity, it should be remembered that R1a1a arose from a single R1a1 Y chromosome and could have done so anywhere that R1a1 had spread at the time R1a1a evolved. Sharma et al. (2009) indicated a site of basal R1a diversity around Bhopal, India with 13 individuals bearing the R1a* mutation, however unlike other study subjects, these R1a were not included as part of the more comprehensive study of Underhill et al. (2009). Mirabal et al. (2009), and Underhill et al. (2009), concluded that there are two separate "poles of the expansion" with similar ages, with South Asian R1a older than European R1a. Of 117 R1a examined from India, none where R1a* or R1a1* (all were R1a1a) contradicting Sharma et al. 2009.

Popular science

Bryan Sykes in his book Blood of the Isles gives (from his imagination) the populations associated with R1a in Europe the name of Sigurd for a clan patriarch, much as he did for mitochondrial haplogroups in his work The Seven Daughters of Eve.

See also

• Human Y-chromosome DNA haplogroups
• Genetics and Archaeogenetics of South Asia
• Pole, Hungarian, two good friends
• Y-DNA haplogroups by ethnic groups
• Nordic R1a Y-DNA Project

Notes

References

Projects

• FTDNA R1a Y-chromosome Haplogroup Project
• R1a International Y-DNA Project
• Danish Demes Regional DNA Project: Y-DNA Haplogroup R1a
• British Isles DNA Project