Haplogroup 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.
R1a is believed to have originated somewhere within this same area in Eurasia, most likely in the area from Eastern Europe to South Asia. Basal origin and phylogenyThe most recent publications on this subject have increased our knowledge of the complexity of the R1a. It has been shown that by far the most commonly found type of R1a, now known as R1a1a, represents only one branch of a bigger "family tree". Haplogroup R1a is derived from R1 by a series of 4 known mutations. One version of R1a, a derivative called R1a1a, is currently the most abundant version. There are two series of mutations that produced this variant. First, 4 known SNPs altered R1a, producing R1a1. Second, 7 SNPs altered R1a1 to create R1a1a. Roots of R1a{|border="0" cellspacing="0" cellpadding="0" align="right" style="text-align:center; background:#ffffff; margin-left: 3em; margin-bottom: 2em;"
|-
|
|}
R1a evolved from R1 (R-M173) from a common male-line ancestor who had SNP mutations M420, M449, M511, M513 etc. It is therefore the sister clade of R1b (defined by the M343 mutation, and others). There is little certainty concerning the places in Eurasia where R1, R1a or R1b evolved, although suggest that "the most distantly related R1a chromosomes, that is, both R1a* and R1a1* [...] have been detected at low frequency in Europe, Turkey, United Arab Emirates, Caucasus and Iran".Different meanings of "R1a"{|border="0" cellspacing="0" cellpadding="0" align="right" style="text-align:center; background:#ffffff; margin-left: 3em; margin-bottom: 2em;"
|+ align = Center | Phyletic schemes for R1a
|-
|
|-
|{{cladogram|title=2009 latest scheme
|clades={{clade
|label1=R1a M420
|1=
}}
}}
|}
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 more comprehensive survey of the known mutations is listed by ISOGG, and an equivalent tree is given in .
Prior to 2009 the mutation SRY1532.2 (or SRY10831.2) defined R1a, and this is also how the term R1a is most often used in publications before 2009.
However the term R1a is also now increasingly used to refer to a broader family including not only R-SRY1532.2/SRY10831.2, but also other related R1 (R-M173) lineages which are (a) not in R1b (R-M343) and (b) which do share other several mutations with R-SRY1532.2/SRY10831.2 including M420. In this newer system, R-SRY1532.2/SRY10831.2 moves from "R1a" to "R1a1".
We can divide what is known of the three levels of the family tree of R1a based on the large survey of as follows:
R1a* (new nomenclature). (Articles published before the discovery of M420 will not have distinguished these from other R1-M173 lineages.) This is defined as M420 positive but SRY1532.2/SRY10831.2 negative. believe this clade or clades to be rare, and have so far found 1/121 Omanis, 2/150 Iranians, 1/164 in the United Arab Emirates, 3/612 in Turkey. Mutations understood to be equivalent to M420 include M449, M511, M513, L62, L63.[ ]R1a1* (old R1a*) SRY1532.2/SRY10831.2 positive, but M17 and/or M198 negative. found 1/51 in Norway, 3/305 in Sweden, 1/57 Greek Macedonians, 1/150 Iranians, 2/734 Ethnic Armenians, 1/141 Kabardians. also found 13/57 people tested from the Saharia tribe of Madhya Pradesh, and 2/51 amongst Kashmir Pandits. SNP mutations understood to be always occurring with SRY10831.2 include M448, M459, and M516.[ ]R1a1a (old R1a1)' is defined in various articles by M17 or M198 (two mutations which always appear together so far). Such lineages make up the dominant majority of all R1a, and most statistical or other analysis is by definition focused upon it. This clade also has some sub-clades of its own, although a large proportion of R-M17/R-M198 has however not yet been categorized into branches defined by mutations, and is therefore referred to as R1a1* (old nomenclature) or R1a1a* (new nomenclature). SNP mutations understood to be always occurring with M17 and M198 include M417, M512, M514, M515, and rs34297606.[ ]
So far, 8 sub-clades of R1a1a are known, however only three subclades are known to have significant frequencies.
- R1a1c (old nomenclature) or R1a1a3 (defined by M64.2, M87, and M204) is apparently rare, found in 1 of 117 males typed in S. Iran.
- R1a1a6 (new nomenclature, defined by M434) was announced in . It was found in 14 people from Pakistan to Oman and is likely to reflect a recent mutation that took place in the area of Pakistan.
- R1a1a7 (defined by M458) was announced in and is the largest sub-clade found so far. It is found almost entirely in Europe, with its highest frequencies in Central and Southern Poland. Part of this sub-clade is further distinguished as R1a1a7a (defined by M334).
Distribution of R1a1a (R-M17 or R-M198), the dominant sub-clade of R1aR1a 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. Throughout all of these regions, R1a is dominated by the R1a1a (R-M17 or R-M198) sub-clade.Central and Northern AsiaR1a 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.South AsiaIn 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 lineagesSouth-West AsiaThe 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. suggest that the deserts of central Iran acted as "significant barriers to gene flow," and propose two possibilities. First, Mesopotamian civilization was densely populated relative to immigrating Indo-Iranians; and second, Indo-Iranian languages may have become the predominant language of all Steppe nomads of various ethnic origins. Whichever model is correct, Western Iranian Y-DNA sampled appears to be more genetically similar to that of Middle Eastern Semitic speakers. found R1a in approximately 20% of males from the cities of Tehran and Isfahan. , 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 of south of Iran and the Dash-e Lut (sic.) 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.EuropeIn Europe, R1a, again almost entirely in the M17/M198 sub-clade, is found at highest levels among peoples of Eastern European descent (Sorbs, Poles, Russians and Ukranians; 50 to 65%).
There is a significant presence in peoples of Scandinavian descent. 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.
In Southern Europe R1a is not normally common but it is widespread and found in significant pockets. found significant levels in the Pas Valley in Northern Spain, and also the areas of Venice, and Calabria in Italy.Origins and hypothesized migrations of R1a1a (R-M17/R-M198)Most recent discussions of R1a origins concern the dominant R1a1a (M17/M198) sub-clade. There are two foci of high frequency of R1a1a (the majority of R1a), one in South Asia, near North India, and the other in Eastern Europe, in the area of the Ukraine. On the one hand, the highest frequency level observed in any large population so far has been found in some South Asian groupsCentral Asian origin proposal argued, Citing data from 3 earlier publications, that R-M17 (R1a1a) Y chromosomes most probably have a central Asian origin. Central Asia is still considered a possible place of origin by after their larger analysis of more recent data. However these authors do not clearly distinguish the case being made for Central Asia for the case being made for Asia, particularly South Asia, more generally.Eastern European migration hypothesesTheories that the earliest generations of R1a1a (M17/M198) men originated in Eastern Europe have become less common with the publication of bigger and more international surveys. However suggestions have been made which associate the distribution of R1a clades with several proposed movements of people in history and prehistory in Eastern Europe. As usual, these suggestions mainly concern the R1a1a sub-clade defined by M17/M198, because this is the dominant R1a clade, and the only one for which there is significant data.
The period from the end of the Ice Age until the Mesolithic. The spread from a Ukrainian refugium during the Late Glacial Maximum.The European Neolithic, for example the LBK (Linear Pottery) Culture and Corded Ware Culture.Bronze Age. The spread of Indoeuropean languages and/or Indo-Aryan languages and/or Indo-Iranian languages in the Bronze Age (also associated with the use of horses, and "Kurgan" burials). Historical Era.' The spread of Slavic languages and migrations in late Classical times.
These three proposals involve very different time periods, but they are not mutually exclusive given that R1a lineages may have been taken part in many different human movements over time in the same geographical region.The period from the end of the Ice Age until the Mesolithic
estimated that R1a1a (M17/M198) dispersed in parts of Europe approximately 11,000 years ago, prior to the Neolithic period. Age estimates of this depth for R1a1a come from papers using the methodology described by , the latest such example being and . (Other methods tend to give much younger estimates for any given set of data.) Researchers using this estimation method therefore believe any Bronze Age or more recent dispersals affecting modern R1a1a diversity can not involve the clade as a whole, but only some branches.Neolithic associates this period specifically with the R-M458 sub-clade, as announced in that article. Once again, it should be noted that this is using the Zhivitovsky age estimation method. Other methods would suggest that a broader section of R1a might have been involved in population movements during the period of the European Neolithic. This stance was espoused as well from studies based on modern sample populations suggesting that the lineage arrived further west into Europe during the Neolithic, specifically with the Corded Ware Horizon. The methods used were Coalescent Theory for Scandinavian groups but also comparing the differentiation levels of R1a to other Y-chromosome haplogroups within in the Baltic region. Bronze Age (Indo Europeans, Indo-Aryans, Kurgans and horses)Theories favoring the second category of these migrations have the additional attraction to some authors that they would seem to link R1a1a (M17/M198) to well-known language dispersals which resulted in the development of the modern Indo-Aryan language family in India, Central Asia, and the Middle East. This popular scenario was linked to the "Kurgan hypothesis" concerning these languages, and these accounts were therefore linked to theories that R1a largely dispersed from Europe (or at least the southeastern edge of Europe) and moved subsequently to Asia.
Such a Bronze Age European origin for R1a1a in at least parts of Asia has also been argued on the basis of a 2009 study of DNA results from Andronovo culture remains in South Siberia. The Y DNA was almost exclusively R1a1 This archaeological culture, has also been genetically studied in Kazakhstan, and is thought to have been a carrier of an Indo-Aryan language (the same family of languages as is commonly associated with R1a in modern India) from the direction of Europe. (In particular it has been noted that their mitochondrial DNA is almost entirely of types associated with Europe, and that this Asian population appears to have had a relatively high level of red and blonde hair and blue eyes.)
Evidence that during and before the Bronze Age R1a existed in Europe to the west of its modern core range, and even west of the Balkans, has come from ancient samples, which appear to show that R1a was common in this region well before Slavic languages are thought to have arrived.[ This was probably R1a1a* (M17/M198 positive, M458 negative) according to .]European migrations within the Historic EraThe spread of Slavic peoples and languages might have played a role in further increasing the frequency of R1a1a (M17/M198) in parts of Europe, but if so then by all age estimates this would have been on sub-clades of R1a1. So this is not an explanation of the origins and dispersal of R1a1 as a whole.
, looking at SNP and STR markers occurring in the Czech Republic suggested there was evidence for a rapid demographic expansion beginning about 60 to 80 generations ago, which would equate to about 1500 years ago (approx. 500 AD) to 2000 years ago (approx. 1 AD) with a generation time of 25 years. Similar results have been found in Lithuania. also detected Y-STR evidence of a recent Slavic expansion from the area of modern Ukraine. This evidence corresponds to population movements during the Migration Period.South Asian origin hypothesisSeveral other studies suggest R1a lineages generally may have their origins in South Asia
As more data has been collated, an increasing number of studies have found South Asia to have the highest diversity of microsatellite Y-STR variation within R1a1a (M17/M198), making it likely that South Asia is the original point of dispersal. Studies which have argued this case most strongly include , , and . Studies which have concluded that the data is at least consistent with this scenario include , and . The latter two articles, being the most recent and comprehensive, both make the case for Asian origins of R1a1a the strongest amongst the various possibilities as of late 2009.
A particular interest has been taken in investigating the long-presumed connection between Indo-Aryan origins and higher caste Brahmins. On the other hand, some authors have not accepted this association.
Age estimation techniques play a role in whether authors accept or reject any connection between Indo-Aryan languages, and R1a in any broad sense. In particular, researchers such as Underhill et al. and Mirabal et al., estimate the dispersal of R1a1a (M17/M198) to have started before conventional estimates of the age of this language family, or it's parent, the Indo-European family.West Asian origin hypothesisAs mentioned above, R1a haplotypes are less common in most of the Middle East than they are in either South Asia or Eastern Europe or Central Asia. It has nevertheless been mentioned in speculation about the origins of the clade.
proposed that a Middle Eastern origin for R1a should be considered, depending upon the strength of arguments for a Middle Eastern origin for Indo-European languages.
Most recently, points out, as did , and that the evidence used to argue for South Asian origins of R1a, does not exclude the possibility of a South-West Asian origin:Popular scienceBryan 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
|
|
