Haplogroup R1a

A subclade of Haplogroup R1, R1a is a Y-chromosome haplogroup "currently found in central and western Asia, India, and in Slavic populations of Eastern Europe".^[1] It has been found in high frequency at both extremes of its range:

In South Asia, in the eastern and northern parts of India, for example among the West Bengal Brahmins, 72%, and Uttar Pradesh Brahmins, 67% of male lineages^[2] 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^[3]. While further to the north, in Central Asia, the Ishkashimi have been tested as 68%, and the Tajik/Khojant 64%. In the western extreme of the central range of R1a, around 50% of male lines amongst Sorbs, Poles, Belarusians, Hungarians and Ukrainians have consistently proven to be R1a positive in various surveys, with slightly lower frequencies being found in mainland Croatia^[4], Slovenia^[5] and amongst Greek Macedonians^[6].

R1a male lineages are also found scattered in significant amounts extending out of these central areas - as far East as Siberia, and as far west as Iberia and the British Isles. There is a significant presence in Scandinavia, whence branches seem to have moved still further west, to Britain with the Vikings. In Iceland, for instance, R1a accounts for nearly a quarter of the Icelandic male Y-DNA. Scozzari et al. (2001) found significant levels in the Pas Valley in Northern Spain, and also the areas of Venice, and Calabria in Italy.

Some earlier studies came to the conclusion that R1a may have arisen 15,000 years ago in the vicinity of Ukraine, possibly expanding from either the Ukrainian LGM refuge following the end of the last ice age, or from the Pontic-Caspian steppe as a result of the hypothetical Kurgan migrations theory.^[6][7][8].

However, some newer studies show that R1a lineages may have their origins in North India ^[2][9][10]. Oxford University's Stephen Oppenheimer in his book The Real Eve: Modern Man's Journey Out Of Africa, agree's with Cambridge geneticist Toomas Kivisild findings in that "For me and for Toomas Kivisild, South Asia is logically the ultimate origin of M17 and his ancestors", and that "one estimate for the age of this line in India is as much as 36,000 years old"^[11].

Origins

R1a's origins remain disputed. It presumably originated somewhere in the Eurasian landmass, where it is most commonly found today. There are two focuses of high frequency of R1a, one in South Asia, near North India, and the other in Eastern Europe, in the area of Ukraine. The highest diversity is measured in the Balkan and Crete.^{[12] [13]} Rival theories each propose one of these geographic locations as the origin of R1a, though with varied suggested dates, while other theories consider the possible role of West Asia.

Eastern European Origin Theories

European LGM refuges, 20 kya.

Although in south eastern Europe overall the R1a haplogroup occurs at just 16% frequency, high-resolution Y chromosome analysis by Pericic et al. (2005) shows a maximum diversity of R1a STR variance among Croatians and Bosnians. While diversity is a recognised signal of a point of origin, it cannot on its own supply a date for the spread from that origin:

At least three major episodes of gene flow might have enhanced R1a variance in the region: early post-LGM recolonizations expanding from the refugium in Ukraine, migrations from northern Pontic steppe between 3,000 and 1,000 B.C., as well as possibly massive Slavic migration from A.D. 5th to 7th centuries.

Passarino et al. (2002) support the Ukrainian LGM refuge scenario, suggesting that R1a expanded from the area of the Dniepr-Don Valley in Ukraine between 13,000 and 7,600 years ago, after the Last Glacial Maximum receded.

Semino et al. (2000) propose two dates of expansion, suggesting that the spread of R1a from a point of origin in Ukraine following the Last Glacial Maximum may have been magnified by the expansion of males from the Kurgan culture area of present-day southern Ukraine, from where, according to Gimbutas proposals,^[14] Indo-European languages spread.

Historical distribution of the Slavic languages. The area shaded in light purple is the Prague-Penkov-Kolochin complex of cultures of the 6th to 7th c. AD, likely corresponding to the spread of Slavic tribes at the time. The area shaded in darker red indicates the core area of Slavic river names (after EIEC p. 524ff.)

Spencer Wells, director of the Genographic Project at the National Geographic Society, identified southern Russia/Ukraine as the likely origin of R1a (as identified by genetic marker M17) on the basis of both microsatellite diversity and frequency distribution.^[15] He enlarged on the correlation of R1a with the expansion of the Kurgan people.

The current distribution of the M17 haplotype is likely to represent traces of an ancient population migration originating in southern Russia/Ukraine, where M17 is found at high frequency(>50%) It is possible that the domestication of the horse in this region around 3,000 B.C. may have driven the migration. The distribution and age of M17 in Europe and Central/Southern Asia is consistent with the inferred movements of these people, who left a clear pattern of archaeological remains known as the Kurgan culture, and are thought to have spoken an early Indo-European language. The decrease in frequency eastward across Siberia to the Altai-Sayan mountains (represented by the Tuvinian population) and Mongolia, and southward into India, overlaps exactly with the inferred migrations of the Indo-Iranians during the period 3,000 to 1,000 B.C.^[7]

Investigation of SNP and STR markers occurring within subgroup R1a1 in the Czech Republic confirmed that the results are compatible with a presence of the gene during or soon after the LGM. Population growth beginning in the first millennium B.C. was detected. The overall diversity suggests 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.^[16] This would correlate with the Slavic expansions.

Stephen Oppenheimer believes after extensive genetic testing and analysis that the Modern "Out of Africa" theory ties in with R1a1 (M17) in that, it "could have found his way initially from India or Pakistan, through Kashmir, then via Central Asia and Russia, before finally coming to Europe"..."as part of an archaeologically dated Paleolithic movement from east to west 30,000 years ago."^[17][18].

South Asian Origin Theories

In a seminal work titled The Real Eve: Modern Man's Journey out of Africa (New York: Carroll and Graf Publishers, 2003), the prominent Oxford University scholar Stephen Oppenheimer concludes that South Asia is the origin of M17 and his ancestors. He observes:

Spencer Wells noted that the Indo-European-speaking Sourashtrans, a population from Tamil Nadu in southern India, have a much higher frequency of M17 [R1a] than their Dravidian-speaking neighbours, the Yadhavas and Kallars, adding to the evidence that M17 [R1a] is a diagnostic Indo-Iranian marker.^[7] However Saha et al. examined R1a1 in South Indian tribals and Dravidian population groups more closely, and questioned this concept. Their analyses of the haplogroups "indicated no single origin from any lineage but a result of a conglomeration of different lineages from time to time. The phylogenetic analyses indicate a high degree of population admixture and a greater genetic proximity for the studied population groups when compared with other world populations".^[19]

A particular interest has been taken in investigating the long-presumed connection between Indo-Aryan origins and high caste Brahmins. Studies have generally failed to support this association. The R1a lineage forms around 35–45% among all the castes in North Indian population (Namita Mukherjee et al. 2001) and the Badagas of the Nilgiris. Sengupta et al. have confirmed R1a's diverse presence even among Indian tribal and lower castes (the so-called untouchables) and populations not part of the caste system. ^[9] Chaubey et al. draw the same conclusion that both caste and tribal populations are autochthonous to India.^[20] S. Sharma et al. aimed aimed to resolve the issue of the origin of caste system in India in their study of a large number of Brahmins, Dalits and Tribals. Overall, no consistent difference was observed in Y-haplogroups distribution between the groups, except for some differences confined to a given geographical region.

Several Indian studies have pressed the case for an Indian origin for R1a1 from the diversity and distinctiveness of microsatellite Y-STR variation. Sengupta et al. conclude that there must have been an independent R1a1 population in India dating back to a much earlier expansion than the Indo-Aryan migration.^[9] Sahoo argued from Y-chromosomal data against any major influx into the Indian subcontinent from regions north and west of India, of people associated either with the development of agriculture or the spread of the Indo-Aryan language family.^[21]

In a study published in the American Journal of Human Genetics by S. Sharma (2007), genetic testing showed the highest frequency (up to 72.22%) of Y-haplogroups R1a1* in Brahmins, hinted at its presence as a founder lineage for this caste group. The associated averaged phylogentic ages for R1a* was (~18,478 years), and R1a1*(~13,768 years)^[22]

West Asian Origin Theories

Kivisild et al. (2003), on the other hand, feel that the same type of evidence used to argue for Southern Asia being the origin of R1a, could also be used to argue for a Western Asian origin.

Semino et al. (2000) 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.

Subclades

• R1a (SRY1532)
  • R1a1 (M17, M198) Typical of Eastern Europeans, Central Asians, and South Asians
    • R1a1a (M56) Found in a significant minority of people of Eastern Europe
    • R1a1b (M157) Found at low frequency in Scotland, Ireland and France
    • R1a1c (M64.2, M87, M204) Found at low frequency in Scotland and Ireland
    • R1a1*
  • R1a*

Distribution

Haplogroup R1a distribution

R1a is "present at high frequency (40 per cent plus) from the Czech Republic across to the Altai Mountains in Siberia and south throughout Central Asia."^[15] To the east, this gene found its way as far as Eastern Siberia, with considerable concentrations in Kamchatka and Chukotka, and it is possible that the gene even entered the Americas by this route.^[23]

The modern population of Ukraine has the highest level of diversity of the gene making it the likeliest location of its origin.^[6][15][24] this map^[25] Even in South Eastern Europe (not a major concentration of R1a1) microsatellite networks of major Y chromosomal lineages show high diveristy of R1a1 (graph C)^[25]. The variance cluster in South Eastern Europe (SEE) is located in the Republic of Macedonia.^{[citation needed]}

more detailed map of Haplogroup R1a distribution

Europe

In Europe, R1a is found primarily in the eastern part of the continent, with the highest frequencies among the Sorbs (63.39%), Poles (56.4%),^[6] , Russians (50.0%)^[26] and Ukrainians (54.0%).^[6][27] An early study reported an R1a frequency of 60.0% among a sample of 45 Hungarians,^[6] but a more recent study found haplogroup R1a Y-DNA in only 20.4% of a sample of 113 Hungarians.^[28] An even more recent study has found haplogroup R1a1a-M17 in approximately 57% of a sample of 53 Hungarians.^[29] The two main directional components of the spread are consistent with an East to West migration as well as a radial spread from the Balkans.^{[citation needed]}

Pericic et al. (2005) suggest three possible explanations for the distribution of R1a variation:

At least three major episodes of gene flow might have enhanced R1a variance in the region: early post-LGM recolonizations expanding from the refugium in Ukraine, migrations from northern Pontic steppe between 3000 and 1000 B.C., as well as possibly massive Slavic migration from A.D. 5th to 7th centuries.

It is likely that Vikings or Normans, Viking descendants, settling in Britain, Scotland and to a lesser degree Ireland^[30], carried the R1a lineage,^[8] which accounts for the small presence of the haplogroup on those islands.^[31][32]

Central Asia

Rosenberg et al. (2006) ran simulations dividing autosomal gene frequencies in selected populations into a given number of clusters. For 7 or more clusters, a cluster (yellow) appears which is nearly unique to the Kalash. Smaller amounts of Kalash gene frequencies join clusters associated with Europe and Middle East (blue) and with South Asia (red).

Exceptionally high frequencies of M17 are found among the Ishkashimi (68%), the Tajik population of Khojant (64%), and the Kyrgyz (63%), but are likely "due to drift, as these populations are less diverse, and are characterized by relatively small numbers of individuals living in isolated mountain valleys."^[7] (The frequency of the Tajik/Dushanbe population is, at 19%, far lower than the 64% frequency of the Tajik/Khojant population.)^[7]

Haplogroup R1a is also common among Mongolic- and Turkic-speaking populations of Northwestern China, such as the Bonan, Dongxiang, Salar, and Uyghur peoples.^[33][34]

India, Iran, Pakistan and Afghanistan (Indo-Iranians)

The frequency of R1a1 in western Iran, as in the Middle East, is about 5% to 10%, 20% in central regions and 35% for the eastern part.^[35] Wells et al. (2001) suggest that the deserts of central Iran acted as "significant barriers to gene flow," and propose two possibilities:

Kivisild et al. (2003) on the other hand "suggests that southern and western Asia might be the source of this haplogroup":

Geneticist Toomas Kivisild of Cambridge University headed a 2003 paper in which comparisons of the diversity of R1a1 (R-M17) haplogroup in Indian, Pakistani, Iranian, Central Asian, Czech and Estonian populations. This study shows, that diversity of R1a1 in India Pakistan and Iran is higher, than in Czechs (40%) and Estonians.Kivisild et al. (2003)

M. Regueiro et al. (2006) on high frequency of rare R1-M173* and R1a-SRY1532 lineages in Iran.[5]

Haplotypes

Modal

The Eastern European Y-DNA-R1a Modal Haplotype can be found in Poland, Lithuania, Belarus and Ukraine. It has spread westwards into Germany, Bohemia, Moravia, Slovakia and Hungary. Ysearch: ANJNY

The English Y-DNA-R1a Modal Haplotype could have spread to the British Isles via the Vikings or Normans. Ysearch: AXEZU

Famous

Clan Donald Clan crest

In 2003 Oxford University researchers traced the Y-chromosome signature of Somerled of Argyll, one of Scotland's greatest warriors who is credited with driving out the Vikings. He was also the founder of Clan Donald and it is through the clan genealogies of the clan that the genetic relation was mapped out.^[36] Somerled belongs to haplogroup R1a1.

In 2005 a study by Professor of Human Genetics Bryan Sykes of Oxford University led to the conclusion that Somerled has possibly 500,000 living descendants - making him the second most common historical ancestor after Genghis Khan^[37] Sykes's research also revealed that while Somerled drove out the Vikings, his roots were themselves Norse.

The Y-DNA sequence is as follows (12 markers):^[38]

Ysearch: YS495

• Tõnu Trubetsky the descendant of Nikita Trubetskoy

Ysearch: WUZG2

• Anderson Cooper also belongs to Y-DNA haplogroup Haplogroup R1a.^[39]

Frequency

R1a frequency is expressed as percentage of population samples.

Europe

	N	R1(xR1a1)	R1a1	source
Sorbs	112	-	63.39	Behar et al. (2003)
Hungarian	45	13.3	60.0	Semino et al. (2000)
Hungarian	113	20.4	20.4	Tambets et al. (2004)
Poles	55	16.4	56.4	Semino et al. (2000), Pericic et al. (2005)
Ukrainian	50	2.0	54.0	Semino et al. (2000), Pericic et al. (2005)
Belarusian	306		50.98	Behar et al. (2003)  ?- Pericic et al. (2005)
Russian	122	7.0	47.0	Pericic et al. (2005)
Belarusian	-		46	Kharkov et al. (2005)
Belarusian	41	10.0	39.0	Pericic et al. (2005)
Ukrainian	-		44	Kharkov et al. (2004)  ?
Ukrainians, Rashkovo	53		41.5	Varzari (2006) ?
Kazan Tatars	38	3	24	Wells et al. (2001)
Russian, North	49	0	43	Wells et al. (2001)
Latvian	34	15.0	41.0	Pericic et al. (2005)
Udmurt	43	11.6	37.2	Semino et al. (2000)
Pomor	28	0	36	Wells et al. (2001)
Macedonians	20	10.0	35.0	Semino et al. (2000)
Moldavians, Karahasan	72		34.7	Varzari (2006)
Lithuanian	38	6	34	Pericic et al. (2005)
Croatian	58	10.3	29.3	Semino et al. (2000)
UK Orkney	26	65	27	Wells et al. (2001)
Gagauzes, Etulia	41		26.8	Varzari (2006)
Czech + Slovakian	45	35.6	26.7	Semino et al. (2000),14
Norwegian	83		26.5	Wells et al. (2001)
Icelander	181	41.4	23.8	Pericic et al. (2005)
Norwegian	87		21.69	Behar et al. (2003)
Moldavians, Sofia	54		20.4	Varzari (2006)
Orcandin	71	66.0	19.7	Pericic et al. (2005)
Swedish (Northern)	48	23.0	19.0	Pericic et al. (2005)
Swedish	110	20.0	17.3	Pericic et al. (2005)
Danish	12	41.7	16.7	Pericic et al. (2005)
Mari	46	0	13.0	Semino et al. (2000)
German	88		12.50	Behar et al. (2003)
German	48	47.9	8.1	Pericic et al. (2005)
Greek	76	27.6	11.8	Semino et al. (2000)
Albanian	51	17.6	9.8	Semino et al. (2000)
Saami	24	8.3	8.3	Semino et al. (2000)
Saami	23	9	22	Wells et al. (2001)
UK Isle of Man	62	15	8	Capelli et al. (2003)
UK Orkney	121	23	7	Capelli et al. (2003)  ?? 7% <> 23% *5
UK	309		~7	Weale et al. (2002) see references
Georgian	63	14.3	7.9	Semino et al. (2000)
Turkish	523	16.3	6.9	Cinnioğlu et al. (2004)
UK Shetland	63	17	6	Capelli et al. (2003)
UK Chippenham	51	16	6	Capelli et al. (2003)
UK Cornwall	52	25	6	Capelli et al. (2003)
Dutch	27	70.4	3.7	Semino et al. (2000)
German	16	50.0	6.2	Semino et al. (2000)
Italian central/north	50	62.0	4.0	Semino et al. (2000)
British	~1000		~4	Capelli et al. (2003)
Irish	222	81.5	0.5	Pericic et al. (2005)
Calabrian	37	32.4	0	Semino et al. (2000)
Sardinian	77	22.1		Semino et al. (2000)
British	25	72	0	Wells et al. (2001)
Poles	913			Kayser et al. (2005)
Germans	1215			Kayser et al. (2005)
Dniester-Carpathian	-		50.06	Varzari (2006)
Gagauzes, Kongaz	48		12.5	Varzari (2006)
Poles	-		913	Kayser et al. (2005)
Germans	-		1215	Kayser et al. (2005)

• 1 Semino et al. (2000)
• 2 Behar et al. (2003)
• 3 Kharkov et al. (2004)
• 4 Kharkov et al. (2005)
• 9 Kayser et al. (2005)
• 10 Varzari (2006)
• 11 Capelli et al. 2003, table 1, more data % < 6
• 13 Weale et al. (2002)

• empty or - = no data in sample.
•  ? = datasets differences, [?-x]:= ^x=# source

Asia

                             N      R1*    R1a1(%)  Sr. Published
West Bengal Brahmins         30            72.22     2 Sharma et al. (2009) 
Uttar Pradesh Brahmins       31            67.74     2 Sharma et al. (2009)  
Kashmiri Gujars              49     2.04   40.86     2 Sharma et al. (2009)  
Kashmiri Pandits             51     11.76  19.61     2 Sharma et al. (2009)
Himachal Pradesh Brahmin     30     5.26   47.37     2 Sharma et al. (2009) 
Gujarat Brahmins             64     9.38   32.81     2 Sharma et al. (2009) 
Uttar Pradesh Kols           38            14.81     2 Sharma et al. (2009) 
Bihar Paswan                 27     11.11  40.74     2 Sharma et al. (2009) 
Madhya Pradesh Saharia       57            28.07     2 Sharma et al. (2009) 
Ishkashimi                   25      4     68        5 Wells et al. (2001)
Tajiks/Khojand               22      0     64        5 Wells et al. (2001)
Chamar - Indian untouchable                60
Tajiks/Dushanbe              16      0     19        5 Wells et al. (2001)
Tajiks/Samarkand             40      10    25        5 Wells et al. (2001)
Ashkenazi Levite Jews        60      11.7  51.7      10 Behar,2003
Kyrgyz                       52      2     63        5 Wells et al. (2001)
Altays(Southern)             96      1     53          V. N. Kharkov et al. (2007)
Tashkent IE                  69      7     47        ?
India Upper Caste            86      -     45.35     8
Sourashtran                  46      0     39        5 Wells et al. (2001)
Abkhazians                   12      8     33        7 Nasidze,2004
Chenchus (India-Drav.)        -      -     26       12  
Uyghur                       49     ≤8.2   28.6        Ruixia Zhou et al. (2007)
Dongxiang                    49     <10    28          Wei Wang et al.,2003
Bonan                        47      0     26          Wei Wang et al.,2003
Salar                        52     <10    17          Wei Wang et al.,2003
Iran (Tehran)                24      4      4        5 Wells et al. (2001)
Iran (Tehran)                80      8     20        7 Nasidze,2004 

Iran (Isfahan)               50      0     18        7 Nasidze,2004
Pashtuns                     96      4.2   44.8        Firasat et al. (2007)
Kalash                       44      2.3   18.2        Firasat et al. (2007)
Burusho                      97      1.0   27.8        Firasat et al. (2007)
Pakistan                    638      5.6   37.1        Firasat et al. (2007)
Pakistan  ??                 85      1.10  16.47     8 ?
Pakistan                    175      0.57  24.43     8 ?
Pakistan south               91      0     31.87     8 ?
India                       728      0     15.8      8 ?
India                       325      0.3   27       12 ? 
Tuvian                       42      2     14        5 Wells et al. (2001)
Abazinians                   14      0     14        7 Nasidze,2004(*7)
Georgians                    77     10     10        7 Nasidze,2004(*7)
Kurd                         17     29     12        5 Wells et al. (2001)
Nenets                       54      4     11        5 Wells et al. (2001)
Syrian                       20     10     10        1

Lebanese                     31     6.4    9.7        Semino et al. (2000)
Turkmen                      21     52.4    4.8        Zerjal et al. (2002)
Turkmen                      30     37      7        5 Wells et al. (2001)
Lezgi(S.Caucasus)            12     17      8        7 Nasidze,2004(*7)
Svans                        25      0      8        7 Nasidze,2004(*7)
Azerbaijanians               72     11      7        7 Nasidze,2004(*7)
Armenians                   100     19      6        7 Nasidze,2004(*7)
Armenians                    47     36      9        5 Wells et al. (2001)
Armenians                   734     32.7    5.0        Weale et al. (2001)
S.Ossetians                  17     12      6        5 Wells et al. (2001)
Kazakhs                      54      6      4        5 Wells et al. (2001)
Chechenians                  19      0      5        7 Nasidze,2004(*7)
Kallar Dravidian             84      0      4        5 Wells et al. (2001)
Mongolian                    24      0      4        5 Wells et al. (2001)
Ossetians (Ardon)            28      0      4        7 Nasidze,2004(*7)
Kazbegi                      25      8      4        7 Nasidze,2004(*7)
India Dravidian (Tribal)    180      -      2.78     8 
Kabardinians                 59      2      2        7 Nasidze,2004(*7)
Lezgi(Dagestan)              25      4      0        7 Nasidze,2004(*7)
Ossetians (Digora)           31      0      0        7 Nasidze,2004(*7)
Rutulians                    24      0      0        7 Nasidze,2004(*7)
Darginians                   26      4      0        7 Nasidze,2004(*7)
Ingushians                   22      0      0        7 Nasidze,2004(*7)
Cambodia                      6      0      0        8 ?
China                       127      0      0        8    
Japan                        23      0      0        8
Siberia                      18      0      0        8 ?
                 

Publications:

• (*5) Wells et al. (2001)
• (*6) Zerjal et al. (2002)
• (*7) Nasidze et al. (2004)
• (*8) Sengupta et al. (2005) table 5, 6 & 7
• (*10)Behar et al. (2003)
• (*12) Kivisild et al. (2003) Fig3 more detailed data for regions, but no caste

Popular culture

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

• Balanovsky et al. (2008), "Two Sources of the Russian Patrilineal Heritage in Their Eurasian Context", AJHG 82 (1): 236–250, doi:10.1016/j.ajhg.2007.09.019, http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B8JDD-4RHHD95-12&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=6c5c574198b6a790be64d988ec6b4d15 
• Bamshad et al. (2001), "Genetic evidence on the origins of Indian caste populations", Genome Research 11 (6): 994–1004, doi:10.1101/gr.GR-1733RR, PMID 11381027, http://www.genome.org/cgi/content/full/11/6/994 .
• Behar et al. (2003), "Multiple Origins of Ashkenazi Levites: Y Chromosome Evidence for Both Near Eastern and European Ancestries" (^{[dead link]} – ^{Scholar search}), Am. J. Hum. Genet. 73: 768–779, doi:10.1086/378506, PMID 13680527, http://www.journals.uchicago.edu/AJHG/journal/issues/v73n4/40097/40097.html . Also at http://www.ucl.ac.uk/tcga/tcgapdf/Behar-AJHG-03.pdf and http://www.familytreedna.com/pdf/400971.pdf
• Capelli et al. (2003), "A Y Chromosome Census of the British Isles", Current Biology 13 (11): 979–84, doi:10.1016/S0960-9822(03)00373-7, http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VRT-48PV5SH-12&_user=10&_coverDate=05%2F27%2F2003&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=0eb0c8ff85bde2ebc2ef136619f57e7a  also at [6]
• Cinnioğlu et al. (2004), "Excavating Y-chromosome haplotype strata in Anatolia", Hum Genet 114: 127, doi:10.1007/s00439-003-1031-4, http://www.springerlink.com/content/q884mpdr929yuye0/fulltext.pdf 
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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