c© Indian Academy of Sciences

RESEARCH ARTICLE

Genetic admixture studies on four in situ evolved, two migrantand twenty-one ethnic populations of Tamil Nadu, south India

G. SUHASINI1,2,3∗, E. SONAA3, S. SHILA3, C. R. SRIKUMARI1, G. JAYARAMAN1 and A. RAMESH1

1Department of Genetics, Dr ALM Post Graduate Institute of Basic Medical Sciences, University of Madras,Chennai 600 113, India

2Department of Surgical Gastroenterology, Centre for Gastrointestinal Bleed, Division of Hepato Biliary PancreaticDiseases and Liver Transplantation, Government Stanley Medical College Hospital, Chennai 600 001, India

3VRR Diagnosis and Research Centre, New No. 87, Burkit Road, T. Nagar, Chennai, India

AbstractWe analysed the genetic structure of ∼1000 samples representing 27 ethnic groups settled in Tamil Nadu, south India, derivedfrom two linguistic families (Dravidians and Indo–Europeans) representing four religious groups (Hinduism, Islam, Chris-tianity and Jainism) using 11 mtDNA markers. Out of 27 ethnic groups, four are in situ populations (Anglo-Indian, LabbaiMuslim, Nadar Christian and south Indian Jain) and two are migrants (Gypsy and north Indian Jain) from north India to TamilNadu, and 21 are native ethnic groups. Six of the markers we used were monomorphic (HaeIII663, HpaI3592, AluI5176,AluI7025, AluI13262, 9-bp deletion) and five markers were polymorphic (DdeI10394, AluI10397, HinfI12308, HincII13259and HaeIII16517). Haplogroup frequencies, genetic affinities and admixture analysis are based on the genotype data of poly-morphic markers observed in these populations. Haplogroup frequencies indicate that various ethnic groups entered TamilNadu during different time periods. Genetic affinities and admixture estimates revealed that the ethnic groups possessingadvanced knowledge of farming cluster in a branch (C), and could be the late arrived settlers as agriculture, was introducedto this region at about 5 to 3 thousand years ago. In situ ethnic groups appear to have arisen at various times as a result ofthe prevailing dominant socio-cultural forces. Hierarchical Hindu caste system created many ethnic groups in the history ofits existence; some of them became isolated for considerable period of time. Over all, among Tamil ethnic groups, in spite ofcaste systems’ rigidity, built in flexibility in the system in the form of hypergamy and hypogamy had allowed maternal geneflow between them.

[Suhasini G., Sonaa E., Shila S., Srikumari C. R., Jayaraman G. and Ramesh A. 2011 Genetic admixture studies on four in situ evolved, twomigrant and twenty-one ethnic populations of Tamil Nadu, south India. J. Genet. 90, 191–202]

Introduction

The contemporary populations of India are known to haveevolved from peopling of India by waves of migrants fromtime to time (Majumder 1998). Therefore, an intensive studyof Indian populations provide deep knowledge about evo-lutionary forces that may be responsible for the diversityof contemporary Indian populations. The north Indian pop-ulations are predominantly Indo–European language speak-ers and south Indian populations are Dravidian speakers(Meenakshi 1995). Among these two linguistic groups, Dra-vidian language speakers are considered to be more ancient(Gadgil et al. 1998). Since Tamil Nadu in south India isan ancient seat of Dravidian culture, focussed study on the

∗For correspondence. E-mail: sgsu@live.com.

inhabitants of this state is expected to provide knowledge onsome of the early inhabitants of India in general, and TamilNadu in particular.

Several studies have been conducted on ethnic groups ofTamil Nadu that varied in the socio-cultural order, usingsomatoscopic, somatometric and genetic markers (Sanghviand Balakrishnan 1981), DNA markers (Wells et al. 2001;Basu et al. 2003; Sitalaxmi et al. 2003; Rajkumar et al. 2004;Kashyap et al. 2006; Kanthimathi et al. 2007; Vijaya et al.2007) and HLA class II polymorphic markers (Pitchappan2002). These studies revealed that many of them were mi-grants to Tamil Nadu from the neighbouring regions and thatthe state harbours people who travelled by southern route fromAfrica. The phylogenetic analysis placed them in a cluster,away from Indo–European speakers (Forster and Matsumura2005; Kanthimathi et al. 2007). Molecular evidence indicates

Keywords. Dravidian; mitochondrial DNA; admixture; south India; human genetics.

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that mtDNA haplogroups M1 and M3 are found on theHorn of Africa, Arabia/Yemen, and Iran along a migrationpath to south India, which is congruent with anthropological,linguistic and archaeological evidence and suggest Africanorigin for the Dravidian speakers (Winters 2008). Sanghviet al. (1981) even identified the ethnic groups of Tamil Nadu:Chakkiliyar, Parayan and Mutracha (Ambalakarar) as themost ancient who belong to the Paleolithic period.

The genetic structure of the Tamil Nadu populations canbe inferred from both matrilocal and patrilocal studies, as mi-gration is gender based. Even though the caste system is rigid,two social rules viz., hypergamy or ‘Anuloma’ (a womanmarrying a man of higher social rank) and hypogamy or‘Pratiloma’ (a woman marrying a man of lower social sta-tus) provides flexibility to the rigid caste system. Reichet al. (2009) tried to point out the admixture in the Indianpopulation beyond the endogamy of ancestral north Indian

(ANI) and ancestral south Indian (ASI) gene pool. We havealso tried to explain the same through our work. Histor-ically, hypogamy has not been encouraged. On the otherhand, in hypergamy women can adopt the caste and socialstatus of the men whom they marry (Bhattacharyya et al.1999). Therefore, examining the female lineages could helpin delineating the genetic structure of the ethnic groupsbetter.

To know the genetic structure (genomic affinities andinterethnic admixture) of ethnic groups settled at varioustime periods in Tamil Nadu, we analysed the maternal lin-eage of 21 ethnic groups of this region and six more Tamilethnic groups studied by Basu et al. (2003) which could begrouped variously based on religion, socio-economic rank-ing in the caste hierarchical structure of the Hindu religion,past traditional occupation, geographical origin and knownin situ evolution (table 1).

Table 1. Ethnological information on the study populations.

LinguisticCategories Population name N Social strata group Traditional occupation/remarks

A. Non-Hindu populationsMigranta) Jain North Indian Jain (NJ) 37 IE Trade/money lending/commerceIn situa) Jain South Indian Jain (SJ) 50 DR Agriculture/tradeb) Christian Anglo-Indian (AI) 38 IE Urban dwellers

Nadar Christian (NC) 46 DR Trade/agriculture/toddy tappingc) Muslim Labbai Muslim (ML) 50 DR Trade

B. Hindu populationsMigrant Gypsy (GP) 44 Low rank IE Seminomadic, denotified community,

hunters, urban dwellersBrahmins Iyengar (IYN) 30 Upper rank DR Priests/scholars

Iyer (IYR) 30 Upper rank DR Priests/scholarsNonBrahminsa) Vellalar Agamudaiya Vellalar (AV) 47 Mid rank DR Agriculture

Kongu Vellala Gounder (KG) 54 Mid rank DRThuluva Vellalar (TV) 51 Mid rank DRVeerakodi Vellalar (VLR) 43 Mid rank DR

b) Scheduled castes Chakkiliyar (CH) 45 Low rank DR Formerly untouchable leather workers,Agricultural labourer

Pallan (PLN) 30 Low rank DR AgricultureParayan (PA) 50 Low rank DR Agricultural labourer

Common originc) Thevar Agamudaiyar (AR) 47 Mid rank DR Agriculture

Kallar (KL) 50 Mid rank DR AgricultureMaravar (MR) 45 Mid rank DR Agriculture

d) Others Ambalakarar (AMB) 30 Mid rank DR Village headsGavara Naidu (GN) 33 Mid rank DR Trade/agricultureMeenavar (MV) 68 Mid rank DR Fishermen (coastal)Nadar Hindu (NH) 51 Mid rank DR Agriculture/trade/toddy tappingNattukkottai Chettiar (NK) 44 High rank DR Trade/commerceReddiyar (RY) 49 Mid rank DR AgricultureSengundar Mudaliar (SM) 50 Mid rank DR WeaversVanniyar (VAN) 30 Mid rank DR Agriculture/tradeYadavar (YR) 51 Mid rank DR Animal husbandry/agriculture

IE, Indo European; DR, Dravidian.

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Methods

Populations

A total of 1000 genomic DNA belonging to 21 ethnic groups(three Indo–European language speaking groups: Anglo-Indian, Gypsy and north Indian Jain; and 18 Tamil ethnicgroups: Muslim Labbai, south Indian Jain, NattukkottaiChettiar, Sengundar Mudaliar, Agamudaiya Vellalar, ThuluvaVellalar, Yadavar, Kallar, Maravar, Agamudaiyar, KonguVellala Gounder, Nadar Hindu, Nadar Christian, Meenavar,Gavara Naidu, Reddiyar, Parayan and Chakkiliyar) werescreened for mtDNA variations. Six more Tamil ethnicgroups studied by Basu et al. (2003) were also included forphylogenetic and admixture analysis. These include: Iyer,Iyengar, Vanniyar, Ambalakarar, Veerakodi Vellalar and Pal-lan. A brief ethnographic information on all these ethnicgroups is given in table 1.

Genetic markers

DNA samples were screened for 11 coding region variationsin mtDNA (HaeIII np 663, HpaI np 3592, AluI np 5176, AluInp 7025, DdeI np 10394, AluI np 10397, HinfI np 12308,HincII np 13259, AluI np 13262, HaeIII np 16517 and 9-bp deletion; Torroni et al. 1993, 1996) to infer the geneflow between the Dravidians and contribution from differentgroups of immigrants to Dravidians.

Statistical analysis

Haploid allele frequencies (mtDNA) were computed bythe gene counting method. Haplotype and haplogroupfrequencies based on 11 loci observed were estimatedusing Arlequin 3.1 software (Excoffier et al. 2005; seetables 1 & 2 in electronic supplementary material at http://www.ias.ac.in/jgenet). Average heterozygosity at fivepolymorphic loci (DdeI10394, AluI10397, Hinf I12308,HincII13259 and HaeIII16517) for each population wasestimated using DISPAN software (http://www.bio.psu.edu/people/faculty/Nei/Lab/dispan2.htm). This software also cal-culates gene diversity (Nei 1973), genetic distance betweenthe populations (Nei 1987) and constructs phylogenetictree by neighbour-joining (NJ) method using the haplotypefrequencies (Ota 1993).

Admixtures of four in situ populations (Anglo-Indian,Labbai Muslim, Nadar Christian and south Indian Jain)and two migrant populations (Gypsy and north Indian Jain)with the 21 ethnic groups of Tamil Nadu, south India; andwithin the 21 ethnic groups were analysed using LEAD-MIX software (Wang 2003) based on haplotype frequen-cies. LEADMIX performs maximum likelihood estimationof admixture proportions in a model where the ancestralpopulation (P0) is split into two parental populations P1 andP2 that evolved independently before they contributed ingenetic proportion p1 and p2 (where, p2 = 1 − p1) to forma hybrid population (Ph).

While estimating the admixture in in situ and migrant pop-ulations, these populations are considered as hybrid (Ph) andthe 21 ethnic groups as parental populations. Similarly, incase of estimating admixture in 21 ethnic groups, each timeone population among the 21 is considered to be hybrid andother 20 as parental population.

Since there would be too many combinations, one popu-lation was always designated as common parental popula-tion (Pn). Thus, we have estimates of admixture proportionsfor the n–1 populations. Individual admixture proportions ofthese n–1 populations were pooled and a single estimate ofadmixture proportion was estimated for the common parentalpopulation (Pn) paired with the remaining n–1 populations.

Since for each pair of parental populations, p1 + p2 = 1,the contribution for any hybrid population by n number ofpopulations have to be adjusted to 1. This is done, by addingadmixture estimates of each population and then adjustingthem to 1, as relative contribution to the hybrid population.Values of the populations, thus obtained if less than one percent is considered to be none contributing.

Results and discussion

Mitochondrial DNA lineages in Tamil ethnic groups

In our study, the mtDNA restriction sites: HaeIII663 (pres-ence denotes haplogroup A), HpaI3592 (presence denoteshaplogroup L), AluI13262 (absence denotes haplogroup C)and the 9-bp deletion (haplogroup B) were monomorphic fortheir ‘absence’; and AluI-5176 (absence denotes haplogroupD) and AluI7025 (absence denotes haplogroup H) restrictionsites were fixed in all populations. The remaining five loci:DdeI10394 and AluI10397 (presence denotes haplogroup Mand absence denotes haplogroup N), Hinf I-12308 (presencedenotes haplogroup U), HincII13259 (absence denotes hap-logroup C) and HaeIII16517 (presence denotes haplogroupF) were polymorphic.

Haplogroup M and N

The early settlers: The South Asian specific haplogroup M,arose before the split of proto-Indians and proto-Orientals

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Table 2. Frequencies (%) of mtDNA haplogroups in ethnic popu-lations of Tamil Nadu.

HaplogroupsPopulations M (%) N (%) U (%) F (%)

AI 27 (71.0) 10 (26.3) 1 (2.60) 0 (0.00)AV 23 (48.9) 19 (40.4) 3 (6.40) 2 (4.30)AR 40 (85.1) 4 (8.5) 3 (6.30) 0 (0.00)CH 43 (95.5) 2 (4.5) 0 (0.00) 0 (0.00)GN 21 (63.7) 5 (15.2) 6 (18.20) 1 (3.00)GP 27 (61.4) 8 (18.2) 8 (18.30) 1 (2.30)KG 23 (46.0) 20 (40.0) 5 (10.00) 2 (4.00)KL 35 (64.8) 14 (25.9) 3 (5.60) 2 (3.70)ML 30 (66.6) 9 (20.0) 6 (13.30) 0 (0.00)MR 33 (48.5) 28 (41.2) 2 (3.00) 5 (7.30)MV 40 (80.0) 7 (14.0) 3 (6.00) 0 (0.00)NC 27 (58.7) 7 (15.2) 12 (26.10) 0 (0.00)NH 37 (72.6) 10 (19.6) 3 (5.90) 1 (2.00)NJ 22 (49.9) 15 (34.0) 6 (13.70) 1 (2.30)NK 14 (37.8) 13 (35.2) 9 (24.30) 1 (2.70)PA 36 (72.0) 10 (20.0) 3 (6.00) 1 (2.00)RY 21 (42.8) 18 (36.7) 7 (14.20) 3 (6.10)SJ 39 (78.0) 11 (22.0) 0 (0.00) 0 (0.00)SM 37 (74.0) 7 (14.0) 5 (10.00) 1 (2.00)TV 25 (49.0) 17 (33.4) 8 (15.70) 1 (2.00)YR 27 (52.9) 14 (27.50) 7 (13.80) 3 (5.90)Total 627 (62.7) 248(24.8) 100 (10) 25 (2.5)

and predated the entry of Indo–Aryans into India (Passarinoet al. 1996). This haplogroup, in the present study, variedin range from 38 per cent (Nattukkottai Chettiar) to 96 percent (Chakkiliyar; table 2). Agamudaiyar, Meenavar, NadarHindu, Parayan, Sengundar Mudaliar also possessed veryhigh values of haplogroup M (≥ 72%).

The high frequency of haplogroup M in Chakkiliyar indi-cates that it could be one of the oldest populations. Four pre-viously studied populations also showed a frequency greaterthan 90 per cent for this haplogroup (Ambalakarar, 90%;West Bengal Brahmins, 90%; Kota, 96.7%; Toto, 96.67%;Roychoudhury et al. 2000; Edwin et al. 2002; Basu et al.2003). Among these four populations, Ambalakarar and Kotabelong to Tamil Nadu, Toto and West Bengal Brahminsbelong to West Bengal. Numerically, the Kota and Toto arevery small in number around 1000 individuals each. Veryhigh frequency of haplogroup M in both these tribes couldbe due to their small size. Overall, in this study, about 63 percent of the individuals possessed haplogroup M. This is con-sistent with the earlier published data (Anderson et al. 1981;Passarino et al. 1996; Barnabas et al. 2000; Roychoudhuryet al. 2000; Edwin et al. 2002; Basu et al. 2003). The in situevolved populations have frequencies comparable with theancient ethnic groups.

Caucasoid element among Tamil ethnic populations: The hap-logroup N is considered to be a pan-Caucasian marker(Roychoudhury et al. 2000). Its presence in Tamil ethnicgroups could imply an admixture of Caucasian (Indo–Aryan)

elements. In this study, haplogroup N varied in range from 5to 42 per cent (table 2). The average frequency of this hap-logroup is 25 per cent. High frequency was observed amongAgamudaiya Vellalar (40.4%), Kongu Vellala Gounder(40%), Maravar (41.20%), Reddiyar (36.7%), north IndianJain (34%) and Thuluva Vellalar (33.4%). It is less frequent(≤ 14%) in ethnic groups who have high values of hap-logroup M. Probably, these ethnic groups arrived later thanthe ethnic groups having higher frequencies of haplogroupM and may be admixed with Caucasoid elements. The insitu evolved Anglo-Indians are expected to have higherfrequency of haplogroup N in view of their known Caucasianparentage in early times of their evolution. However, its fre-quency about 26 per cent is even much below the valuesobserved in some ethnic castes of this study. This low fre-quency could be due to small contribution of the founderfemale Caucasoids in comparison to male and the resultanthybrids probably being married back to the ethnic groups thathave higher frequency of haplogroup M.

The scheduled castes versus other ethnic groups: The hap-logroup M was below the average frequency (63%) inVellalars (Agamudaiya Vellalar, Kongu Vellala Gounder andThuluva Vellalar), Maravar, north Indian Jain, NattukkottaiChettiar and Reddiyar (≤ 50%). High values (≥ 72%) wereobserved in schedule caste populations (Chakkiliyar, Pallanand Parayan; table 2). This means that schedule caste popu-lations could be the older inhabitants of this region than theformer. These results are consistent with an earlier study onanthropometric variation of Tamil ethnic groups (Malhotraet al. 1981). This study includes some of the present studypopulations. They observed that proto-Australoids, beingdarkest, are the oldest and might have lived in this region20 to 15 thousand years ago (kya). According to them, theseanthropometric elements are present in scheduled castes(Chakkiliyar and Parayan) and in some low rank populations(Mutracha).

Subdivision by religion—Nadar Hindu and Nadar Christian:The religious subdivision of Nadars is expected to bringsome differentiation between them. Large scale conversionto Christianity dates to about 200 years ago (Singh 1997).Conversion to Christianity allowed admixture with other eth-nic groups at greater pace than would have been possible.The haplogroup M was less frequent in Nadar Christian(59%) than in Nadar Hindu (73%; table 2). This suggeststhat Nadar Christians admixed more with the ethnic popula-tions that had less frequency of haplogroup M (AgamudaiyaVellalar, Kongu Vellala Gounder, Maravar, Reddiyar, ThuluvaVellalar and Yadavar).

Common ancestry of Thevar groups—Agamudaiyar, Kallar andMaravar: The Thevar groups consider themselves to havea common ancestry (Singh 1997). They showed substantialvariation in the frequency of haplogroup M (Agamudaiyar,

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85%; Kallar, 65%; Maravar, 49%; table 2). This diversitycould be accounted to unequal splitting and admixture withthe late arrived ethnic groups and who may have high fre-quencies of haplogroup N.

Haplogroup B

The African foot prints in Tamil ethnic groups: The 9-bp dele-tion marker (location np 8272 – np 8289) arose in cen-tral Asia on -/- background (DdeI-10394 and AluI-10397;Haplogroup B) and is reported to have migrated to parts ofsoutheast Asia (Ballinger et al. 1992). This marker is absentin all the studied ethnic groups. Thus, there is least possibilityof Tamil ethnic groups being descendants of central/southernChina migrants.

Haplogroup U

The west Eurasian marker: Presence of HinfI-12308 restric-tion site with -/- background (DdeI-10394 and AluI-10397)was designated as haplogroup U. Its presence is consideredto be a west Eurasian marker and its absence in the context ofIndia implies lack of admixture with the Indo–Aryan ethnicgroups (Roychoudhury et al. 2000). Overall, this haplogroupaccounts for about 10 per cent of the individuals genotyped.Roychoudhury et al. (2000) reported an overall frequency of14.28 per cent for this haplogroup among Indian populations.In Europeans, the average frequency of this haplogroup isabout 25 per cent (http://www.mitomap.org/cgi-bin/tbl5gen.pl). High values (≥ 15%) have been found in Gavara Naidu,Gypsy, Nadar Christian, Nattukkottai Chettiar and ThuluvaVellalar (table 2). This indicates probable contribution ofwest Eurasians to these populations. In Chakkiliyar and southIndian Jain, this haplogroup is absent.

Haplogroup F

The southeast Asian haplogroup: The southeast Asian Hap-logroup F is characterized by the presence of HaeIII-16517 and absence of HincII-12406 restriction sites in -/-background (DdeI-10394 and AluI-10397). This haplogroupaccounts for over 25 per cent of the southeast Asians. Itspresence in the Indian population means contribution by SinoTibetan language speakers during their expansion around 6 to8 kya (https://www3.nationalgeographic.com/genographic/atlas.html?card=mm017). This haplogroup is absent in allin situ populations and in Agamudaiyar, Meenavar andChakkiliyar. In the remaining populations, its frequency var-ied from ∼2 to 8 per cent (table 2). This haplogroup is mostlyfound in the northeast Indian tribes (∼16%; Cordaux et al.2003), Andamanese (10%) and Nicobarese (50%; Thangarajet al. 2003), Vietnamese (32%) and Chinese (10.8%; Tolket al. 2001). In this study, values closer to 8 per cent werefound in Maravar (7.3%), Reddiyar (6.1%) and Yadavar(5.9%). Therefore, it could be inferred that the Tamil ethnicgroups had experienced some gene flow from southeast Asia.

Genetic distance and affinities

Gene diversity: The gene differentiation between the 21 Tamilethnic groups (Gst) is 7.62 per cent (P < 0.005) and increasesto 8.24 per cent (P < 0.005) with the inclusion of six Tamilethnic groups from an earlier study of Basu et al. (2003)(see tables 2 & 3 in electronic supplementary material). Nochange in Gst was observed if the migrant and in situ eth-nic groups were excluded (8.53; P < 0.005). The migrantand in situ ethnic groups themselves have a lower Gst value,5.76 per cent (P < 0.005). The variation in the magnitudeof gene differentiation among the different groups analysedcould be due to their inherent diversity.

Genetic affinities: The genomic affinities revealed by theunrooted NJ tree highlighted some features (see figure 1).The 27 ethnic populations aligned neatly into two branches(C and D) that signify broad cultural division existing amongthem. The ‘most ancient’ populations clustered in one branch(D), whereas the ‘culturally most advanced’ ethnic groupsclustered in another branch (C).

Figure 1. Neighbour-joining tree of 27 ethnic populations basedon mtDNA haplotype. Nomenclature of the NJ tree, A and B, ances-tral and derived node; C and D, branch; C1, C2, D1 and D2 -sub-branch; C1a, C2a, D1a, D1b and D2a, clade; C1a1, D1a1,D1b1, D1b2 and D2a1, subclade; C1a1.1, C1a1.2, D1a1.1, D1b1.1and D1b2.1, cluster; C1a1.11, C1a1.21 and D1b1.11, subcluster.

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Cultural gradient: Kallar, Maravar, Parayan, Agamudaiyar,Chakkiliyar, Pallan, Ambalakarar and Meenavar who occupylower social strata among nonBrahmins and are culturally lessadvanced cluster on branch D. Kallar, Parayan, Chakkiliyarand Ambalakarar (Mutracha) could have settled in this regionabout 20 to 10 kya (Malhotra et al. 1981). This means thatculturally less advanced may be the early settlers. This clus-tering is consistent with the findings of Undevia et al. (1981)who also analysed the genetic affinities of Tamil ethnicgroups using classical genetic markers. According to them,low rank nonBrahmins (like Vanniyar, Kallar and Mutrachaor Ambalakarar) are closely affiliated with the Harijans(Parayan and Chakkiliyar), whereas Kongu Vellala Gounder,Thuluva Vellalar, Reddiyar and Agamudaiya Vellalar whoare traditional agriculturists and occupy higher social strataamong nonBrahmins were clustered in branch C (figure 1).Agriculture was introduced to this region about 3 kya(Cavalli-Sforza et al. 1994) and they could be considered as‘late’ arrived settlers with advanced skills in farming.

Exceptional features of branch D: Iyer and Iyengar (Brahmins,priestly communities), Nattukkottai Chettiar (trading com-munity) and Veerakodi Vellalar (traditional agriculturist com-munity) clustered with the lower strata nonBrahmin groups.

Exceptional features of branch C: The Nadars (toddy tap-pers and traders), Gavara Naidu (agriculturists and traders),Vanniyar (equivalent to Kshatriyas of north India) andYadavar (animal husbandry and agriculture) cluster alongwith traditional agriculture ethnic groups.

In situ populations: Nadar Christians cluster with relativelyadvanced ethnic groups of branch C, whereas Anglo-Indian,south Indian Jain and Muslim Labbai cluster with moreancient ethnic groups of branch D. This could be due to theirvariation in origin. Nadar Christian are considered to havesplit from Nadar Hindu some 200 years ago (Singh 1997),probably admixed with the Christians of other ethnic groups.

The branch D in situ populations showed a pattern of clus-tering which depicts their ancestry and origin. The southIndian Jains are the earliest in situ ethnic group to have orig-inated during 3rd century BC, when a well defined castesystem did not exist (Singh 1997). They formed a closecluster with Ambalakarar (Mutracha) and, together withAnglo-Indians, formed a subclade, D1b2. This subclade withsubclade D1b1 that consists of early settlers (Agamudaiyar,Chakkiliyar, Meenavar, Parayan and Sengundar Mudaliar)formed a clade, D1b (figure 1). Conversion into Jainism fromamong these early settlers and subsequent inbreeding mightbe responsible for the evolution of south Indian Jain.

Anglo-Indians, initially originated as a result of rela-tionships between immigrant Europeans and Indian ethnicgroups (Thurston 1975), especially those occupying lowerstrata of the society. In subsequent generations, the first gen-eration hybrids might have maintained relations more with

the Tamil ethnic groups or among themselves. The entry ofEuropeans into India dates to the period of 15th to 18th cen-tury AD (Richards 1997). The Caucasian heredity amongAnglo-Indians might have been diluted. They are placedcloser towards the low-rank Indian ethnic groups.

Muslim Labbai (Sunni) are believed to be either convertsfrom Hindu castes or born out of marital relationship betweenimmigrant Muslim and natives (Singh 1997). Kivisild et al.(2003) and Terreros et al. (2007) in their studies observedthat Sunni Muslims are mostly descendants of Hindu con-verts. Islam has substantial influence all over the Indian sub-continent. They found the near-east mtDNA haplogroup R—which is common among Indians, in Indian Sunni Muslimsalso. Muslim Labbai showed closer affinity with Brahmingroups. Jasti et al. (2008) who analysed the genetic affini-ties of two south Indian Brahmin groups and Sunni Muslimsusing HLA class II (DRB1) observe that Muslims might havebeen the result of admixture between Indo–Europeans andproto-Dravidians. On the other hand, Brahmins are consid-ered to possess Caucasian elements and migrant to southIndia (Mahadevan 2008). This suggests a shared hereditybetween Muslim Labbai and Brahmins.

Migrants: The migrant populations from northwest India—north Indian Jain and Gypsy clustered along with the sub-clade, C1a1. North Indian Jain (trading community) formed aclose cluster with Kongu Vellala Gounder (agriculture com-munity). The Gypsy (semi nomadic community) formed aclose cluster with Nadar Hindu (toddy trappers and traders).Their relations are unexpected and cannot be explained withthe known ethno histories of the groups.

Genomic affinities of branch D ethnic groups: The Chakkiliyar(Harijans) and Agamudaiyar (low rank nonBrahmin) formeda deep rooted cluster. This unexpected relationship remainedunchanged even with the removal of in situ and migrantgroups. The close relationship observed in this study could beexplained only by assuming shared ancestry. Malhotra et al.(1981) observed that Chakkiliyar could be the early settlersof Tamil Nadu dating to 20 kya.

The Sengundar Mudaliar (weaver community), Parayan(Harijans) and Meenavar (marine fisherfolk) formed inde-pendent clusters in subclade, D1b1 and are closer with theChakkiliyar and Agamudaiyar who formed a close clusterin the same subclade. Closer affinity between Meenavar andParayan was observed in an earlier study of Kanthimathiet al. (2008) who used autosomal markers. In another study,both Chakkiliyar and Parayan were reported to have proto-Australoid racial elements (Malhotra et al. 1981). The closegenetic affinities between Parayan, Meenavar and Chakkiliyarcould arise if they share a common ancestral group. Like-wise, all the ethnic groups of subclade, D1b1 could have hada common ancestor.

The close genetic affinity between the two Brahmin groups:Iyer and Iyengar might be due to the well known fact thatthe latter arose from the former as a split group during

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Genetic structure of Tamil Nadu ethnic groups

12th century (Sanghvi and Balakrishnan 1981). Brahmingroups, along with Muslim Labbai and Nattukkottai Chettiarformed a subbranch, D2. Their affinity with other groups ofbranch D indicates a possible flow of heredity from the lat-ter. This is not surprising if one considers the ‘Anuloma’ and‘Pratiloma’ exceptions to the theoretically rigid Hindu reli-gious caste/subcaste endogamy. These exceptions allow thegene flow from castes of lower status to the castes of higherstatus and vice-versa (Sanghvi and Balakrishnan 1981;Balakrishnan et al. 1996). Historically, ‘Pratiloma’ has beendiscouraged and men rarely cross caste boundaries. Womenwere allowed to adopt the caste and social status of the menwhom they marry (Bhattacharyya et al. 1999). The interme-diate position of Brahmins (Iyer and Iyengar) between sub-branch D1 and branch C indicate sharing of their hereditywith the populations of these two extreme groups. Ethnicgroups like Mudaliar, Vellalar, Chettiar, Brahmin and Naiduspossess Western branchycephalic racial elements and theymight have entered the region at least 5 to 3 kya (Malhotraet al. 1981).

The Thevar groups or Mukkulathor: Agamudaiyar, Maravarand Kallar were found in different subclades of branchD. Maravar formed a close cluster with Veerakodi Vellalar(figure 1, D1a1.1). They are one among the Vellalar groupsand their main occupation is agriculture (Singh 1997). Kallarformed a close cluster with them. Pallan formed a separatecluster in clade D1a. Among them, Kallar were reportedto possess Mediterranean racial elements and said to havemigrated into this region some 10 kya (Malhotra et al.1981). Maravar are considered to be a subdivision of Kallar(Thurston 1975). Pallan an agricultural community rankshighest among scheduled castes (Ramaiah 2004; Census ofIndia 2001). Maravar forming a close cluster with VeerakodiVellalar rather than with Kallar is surprising. Likewise,Pallan clustering with these populations rather than withother scheduled caste populations is unexpected. The geneticaffinities of Thevar groups could be explained partly bygeographical expansion, split and admixture with diverseneighbourhood groups.

Genomic affinities of branch C ethnic groups: Yadavar showedcloser affinity with Vanniyar. They inturn, cluster withAgamudaiya Vellalar to form a subbranch C2 (figure 1).Wells et al. (2001) reported that Yadavar of Madurai, southIndia, have haplogroup J2 derived from haplogroup J of Ychromosome about 10 kya. Haplogroup J2 represents theagricultural innovators who followed the rainfall (Chiaroniet al. 2008), and is more frequent among Mediterraneans(Semino et al. 2004). This shows that the ancestors ofYadavar might have entered India 10 kya or even earlier andlater entered the Tamil speaking region. Their close affin-ity with Vanniyar who possess paleo-Mediterranean racialelements (Malhotra et al. 1981) could be due to sharedheredity, and close relationship with Agamudaiya Vellalarcould be due to admixture.

Kongu Vellala Gounder, Thuluva Vellalar, AgamudaiyaVellalar were placed in branch C and Veerakodi Vellalaralone were placed in branch D. Vellalars, Brahmins, Mudaliar,Chettiar and Naidu possess Western brachycephalic racialelements (Malhotra et al. 1981) and therefore, expected tocluster in one branch. Veerakodi Vellalar being placed indifferent branch could be due to differential gene flow.

Admixture analysis

Admixture analysis is expected to shed more light on inter-relationships of the ethnic groups. An equitable exchangebetween populations refers to the absence of social processesthat inhibit biological exchange of genes, likewise in reverse,gene flow between ethnic groups implies the existence ofsocial restrictions and an unequal exchange means greaterinfluence of highly contributing population. Through admix-ture analysis one could find out which of the 21 native ethnicgroups contributed to the evolution of in situ populations andthe extent to which the migrant populations absorbed genesfrom the natives (table 3).

In situ populations: admixture by Tamil speaking ethnicpopulations

South Indian Jains, Muslim Labbai, Nadar Christians andAnglo-Indian have evolved in situ when one or otherreligion predominantly patronized by the ruling class at dif-ferent periods in the history of the Indian subcontinent.The contribution of mitochondrial genes by the 21 Tamil

Table 3. Admixture proportion of in situ and migrant populationsbased on mtDNA polymorphic markers.

HybridIn situ Migrant

Parental SJ NC ML AI NJ GP

AV 0.0005 0.0857 0.0521 0.0710 0.0519 0.0811AMB 0.1045 0.0001 0.0154 0.0052 0.0153 0.0173AR 0.0008 0.0002 0.0003 0.0003 0.0003 0.0037CH 0.0942 0.0001 0.0001 0.0002 0.0001 0.0002GN 0.0003 0.0403 0.0003 0.0003 0.0003 0.0814IYN 0.0003 0.0088 0.0919 0.1521 0.0914 0.0814IYR 0.0003 0.0863 0.0347 0.0002 0.0346 0.0023KG 0.0003 0.0862 0.0290 0.1672 0.0289 0.0812KL 0.2390 0.0643 0.1386 0.1687 0.1379 0.0814MR 0.0020 0.0002 0.0260 0.0019 0.0259 0.0001MV 0.0168 0.0863 0.0003 0.0052 0.0003 0.0814NH 0.0659 0.0863 0.0001 0.0552 0.0001 0.0814NK 0.0003 0.0682 0.0261 0.0003 0.0260 0.0001PLN 0.0158 0.0649 0.1162 0.1644 0.1156 0.0813RY 0.0003 0.0863 0.0367 0.0002 0.0365 0.0814SM 0.1463 0.0631 0.1312 0.0078 0.1305 0.0813TV 0.0003 0.0863 0.0609 0.0078 0.0655 0.0814VAN 0.0000 0.0863 0.0869 0.0858 0.0864 0.0814VLR 0.0626 0.0001 0.0835 0.1056 0.0831 0.0001YR 0.0003 0.0001 0.0692 0.0003 0.0689 0.0001PA 0.2497 0.0002 0.0005 0.0003 0.0005 0.0002Total 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000

Journal of Genetics, Vol. 90, No. 2, August 2011 197

G. Suhasini et al.

speaking ethnic groups to the evolution of four in situpopulations are presented in table 3.

South Indian Jain belongs to Digambar sect of Jainism.During 3rd or 4th century AD, Jainism and Buddhism ex-isted side by side with Brahmanism when there was noSaivism or Vaishnavism (Singh 1997). Parayan, Kallar,Sengundar Mudaliar, Ambalakarar, Chakkiliyar, VeerakodiVellalar, Meenavar and Pallan contributed about 93 percent of the admixed genes. Brahmins, Vanniyar, Chettiar,Yadavar, Reddiyar, Gavara Naidu and Vellalars (excludingVeerakodi Vellalar) have not contributed to the south IndianJains. It is obvious that Jainism as a religion had tremen-dous influence on early settlers and least influence on latearrived migrants. A significant observation is that, the twoscheduled caste populations viz., Parayan and Chakkiliyarcontributed exclusively to the south Indian Jain but not tothe other in situ populations. Iyengar, Pallan, Kallar andVeerakodi Vellalar of branch D together account for about2/3rd of the Anglo-Indians’ admixed mitochondrial genes.Kongu Vellala Gounder, Nadar Hindu, Agamudaiya Vellalarand Vanniyar of branch C accounted for the remaining 1/3rdof the admixed mitochondrial genes. Thus, both early andlate arrived settlers contributed to the evolution of Anglo-Indians. Fifteen ethnic groups contributed to the MuslimLabbai. This reflects larger influence of Islam over the Indiansubcontinent even though it arrived as late as 12th cen-tury (Thurston 1975). However, Chakkiliyar, Agamudaiyar,Meenavar, Parayan, Nadars and Gavara Naidu have not con-tributed to Muslim Labbai. It means that Islam as a religionhas little or no influence on early settlers.

It is surprising to note that the magnitude of contribu-tion by Nadar Hindu is of comparable magnitude with thecontributions of some seven other populations (AgamudaiyaVellalar, Kongu Vellala Gounder, Iyer, Meenavar, Reddiyar,Thuluva Vellalar and Vanniyar) when one expects a largercontribution due to their reported large scale conversioninto Christianity during 16th to 19th century (Cavalli-Sforzaet al. 1994). The Nadar Christian might have evolved byinitial split from Nadar Hindu and subsequent admixturewith other similarly converted ethnic groups who might havegiven up ethnic identity perhaps due to their conversionin smaller numbers over a longer period. Branch C ethnicgroups contribution is much greater (∼58%) than those ofbranch D (∼38%). Overall, Christianity has less influence onearly settlers than on the late arrived ethnic groups. Theseinfer that south Indian Jain was the earliest among in situpopulations. Anglo-Indians could have arisen next to them.Nadar Christian, as known today originated later to Anglo-Indians; and the Muslim Labbai originated earlier to theNadar Christians.

Migrant populations: admixture by Tamil speaking ethnicpopulations

North Indian Jain and Gypsy are well-known pan-Indian eth-nic groups due to the very nature of their occupation and

differing culture. North Indian Jain belongs to the Svetam-bar sect of Jainism settled all over India in almost all impor-tant urban areas and work as money lenders, traders andindustrialists. They trace their origin to northwest India. Gyp-sys live as nomads on urban pavements, semiurban and inurban peripheral areas (Singh 1997). North Indian Jain re-ceived mitochondrial genes more from branch D populations(∼66%) than from branch C populations (∼34%). None ofthe early settlers (Chakkiliyar, Parayan, Ambalakarar andMeenavar) did contribute to them. This is in contrast to theobservations made in south Indian Jain. This implies thatthe north Indian Jains were not responsible for the originand evolution of south Indian Jain. Branch C ethnic groups(excluding Yadavar; ∼56%) contribution to Gypsy is greaterthan those of branch D (∼42%) ethnic groups. Chakkiliyar,Parayan, Ambalakarar, Nattukkottai Chettiar, Iyer and Maravarof branch D did not contribute to Gypsy.

Socio-economic groups-admixture with other Tamil ethnic groups

Scheduled castes: Scheduled castes (Chakkiliyar, Parayan andPallan) also collectively known as ‘Dalits’ or ‘Harijans’,were treated as ‘untouchables’ by other ethnic groups forsubstantial part of their evolution. Pallan and Chakkiliyaroccupy the highest and lowest status among them, respec-tively (Census of India 2001). Chakkiliyar and Parayanare known to possess proto-Australoid elements (Malhotraet al. 1981). Chakkiliyar had no exchange of mitochondrialgenes with 15 ethnic groups. Even with those they haveexchanged, the exchange is always unequal. They receivedfar more than they could contribute. Pallan contributed sub-stantially but did not receive genes from the Chakkiliyar.Though Chakkiliyar and Parayan showed substantial differ-ence in admixture they had with other ethnic groups, the for-mer is almost ‘isolated’ while the latter exchanged, fairlywith a large number of ethnic groups. This is largely due tomenial jobs that were assigned to Chakkiliyars by the soci-ety at large. Pallan who occupy the highest status among thescheduled castes and reasonably well advanced in farming(Singh 1997) contributed mitochondrial genes to all the eth-nic groups and also had equitable exchange with Kallar, oneof the ancient populations settled in Tamil region about 10kya (Wells et al. 2001).

Thevars or Mukkulathors: Agamudaiyar, Kallar and Maravaralso known as Thevars, consider themselves to be originat-ed from common ancestor. In the NJ tree they were placedin separate clades of subbranch D1. Kallar and Maravarwere placed in one clade. Kallar, the oldest immigrantsof Neolithic period with Mediterranean racial elements(Wells et al. 2001) had equitable exchange with SengundarMudaliar and Maravar. They had unequal exchange of geneswith Pallan. They had not exchanged with Agamudaiyar,Chakkiliyar, Gavara Naidu and Meenavar. Their close rela-tionship with branch D ethnic groups is fully justified con-sidering the exchange of mitochondrial genes with them.

198 Journal of Genetics, Vol. 90, No. 2, August 2011

Genetic structure of Tamil Nadu ethnic groups

Kallar contributed more genes to Maravar than what theycould receive from the latter. This suggests that initiallyMaravar could have evolved from Kallar as a split groupand later admixed with other ethnic groups. This means thatKallar and Maravar could have shared heredity. Agamudaiyarformed a close cluster with Chakkiliyar, an early settler ofthe region some 20 to 15 kya (Malhotra et al. 1981). Inadmixture analysis, Agamudaiyar exchanged mitochondrialgenes with scheduled castes, Gavara Naidu, Ambalakarar,Meenavar and Nadar Hindu. Apart from Kallar and Maravar,they had not exchanged mitochondrial genes with 11 ethnicgroups. Like Chakkiliyar they are an ‘isolated’ ethnic group.Although, they are part of Thevar group, genetically theyshowed greater proximity to the Chakkiliyar.

Religious subdivision

Nadars: Traditionally, Nadars are toddy tappers who lateradopted trade and agriculture as primary occupations. By19th century, Christianity influenced them so much so thatthey split into two subgroups: Nadar Hindu and NadarChristian (Singh 1997). Overall, Nadar Hindu has exchangedmitochondrial genes with the culturally less advanced eth-nic groups of branch D than with branch C ethnic groups(figure 1; table 4). This could be a reason for its reloca-tion from branch C to branch D when in situ and migrantpopulations were excluded (figure 2). Due to the influenceof Christianity, the split group, Nadar Christian later couldhave admixed with relatively advanced ethnic groups whowere also influenced by Christianity. Nadar Hindu contin-ued to maintain exchange with early settlers and with NadarChristians too.

Traditional Agriculturists—The Vellalars: Vellalars are subdi-vided into four subgroups corresponding to their specificancient geographical areas of inhabitance in Tamil Nadu viz.,Pandya (Agamudaiya Vellalar), Kongu (Kongu VellalaGounder), Thondaimandalam (Thuluva Vellalar) and Soliya(Veerakodi Vellalar; Thurston 1975). These populationswhich share a common suffix Vellalar and with similar occu-pation are expected to be genetically closer. AgamudaiyaVellalar, Kongu Vellala Gounder and Thuluva Vellalar hadequitable exchange of genes among themselves. This impliesthat with exception of Veerakodi Vellalar other Vellalars didnot have social constrains to exchange genes among them.Veerakodi Vellalar had greater affinity towards branch Dpopulations, whereas other Vellalars did exchange more withthe branch C ethnic groups (table 4).

Brahmins: Brahmins occupy highest social status in theHindu caste hierarchy. In Tamil Nadu, Brahmins belong totwo major groups: Iyer and Iyengar. The latter are con-sidered to be a split group of the former who admixedwith other ethnic groups (Sanghvi and Balakrishnan 1981).They are supposed to have entered this region about 5 to 3kya (Malhotra et al. 1981). Iyengar received mitochondrial

genes from the Iyer greater than they contributed to them.Brahmin groups did not exchange the genes with Agamu-daiyar, Chakkiliyar, Gavara Naidu, Meenavar, Nadar Hinduand Parayan. Iyengar had equitable exchange of genes withAgamudaiya Vellalar and Vanniyar. With the remaining pop-ulations they had unequal exchange of genes. Thus Brahminsexchanged with both branch D and C ethnic groups and thisis reflected in NJ tree (figure 1). After their split, they couldhave independently admixed with other culturally advancedethnic groups.

Other ethnic groups: Reddiyar and Gavara Naidu are knownto be a Telugu speaking migrant from Andhra Pradesh dur-ing the period of Vijayanagar empire (16th century; Sanghviet al. 1981). Traditionally they are agriculturists. In the ear-lier study on Reddiyar using autosomal markers, Vijayaet al. (2007) found them to cluster along with most ancientethnic groups. In contrast, in this study they were clusteredwith the Vellalars. They exchanged more with branch C thanwith subbranch D2 ethnic groups. This implies that theymight have arrived later than the early settlers. Being anagricultural community, they could have shared mitochon-drial genes more with the Vellalar groups. Being landowners,their clustering with the early settlers in the previous studyis not totally unexpected. Surprisingly, Gavara Naidu had noexchange of mitochondrial genes with Reddiyar, rather hadunilateral exchange with Agamudaiya Vellalar, Chakkiliyar,Thuluva Vellalar and Vanniyar and equitable exchange withNadar Hindu.

Ambalakarar or Mutracha are known to be early set-tlers of Tamil region (Malhotra et al. 1981). They havereceived mitochondrial genes from Agamudaiyar, Chakkili-yar, Gavara Naidu, Iyengar, Kallar, Meenavar, Nadar Hindu,Pallan, Sengundar Mudaliar, Vanniyar, Veerakodi Vellalarand Parayan almost in equal proportion, but contributed toonly some of them (table 4).

Meenavar are fisherfolk inhabiting the coastal line ofTamil Nadu. They are known to be highly influenced byChristianity (Singh 1997). In NJ tree they formed subclusterD1b1.11 with Agamudaiyar and Chakkiliyar (figure 1). Withautosomal DNA markers also they formed a close clusterwith Parayan, an earliest settler of this region (Kanthimathiet al. 2008). Meenavar contributed unilaterally to Aga-mudaiyar and Chakkiliyar and had bilateral but unequalexchange with Parayan. They had equitable exchange withNadar Hindu and contributed to Nadar Christian also. LikeChakkiliyar and Agamudaiyar, they had exchanged genesonly with nine ethnic groups. Based on their biological prox-imity with the Parayan, Meenavar could be considered ascontemporaneous of Parayan and probably isolated by wayof their specialized occupation, marine fishing.

Nattukkottai Chettiar, a numerically small trading com-munity (size, 94,260; Second Backward Class Commission1989), occupy the highest position among nonBrahmins(Singh 1997). Admixture proportions imply that they hadexchanged mitochondrial genes more with the ethnic groups

Journal of Genetics, Vol. 90, No. 2, August 2011 199

G. Suhasini et al.

Tabl

e4.

Adm

ixtu

repr

opor

tion

of21

ethn

icpo

pula

tions

ofTa

mil

Nad

uba

sed

onm

tDN

Apo

lym

orph

icm

arke

rs.

Hyb

ridPa

rent

alAV

AM

BA

RC

HG

NIY

NIY

RK

GK

LM

RM

VN

HN

KPL

NRY

SMTV

VAN

VLR

YR

PA

AV0.

0000

0.00

000.

0000

0.00

030.

0886

0.08

120.

0870

0.06

600.

0723

0.00

020.

0000

0.06

920.

0230

0.10

060.

0393

0.08

330.

0850

0.11

360.

0907

0.00

02A

MB

0.04

330.

0265

0.08

870.

0393

0.00

010.

0001

0.00

010.

0436

0.00

010.

0675

0.08

220.

0002

0.04

020.

0001

0.05

180.

0001

0.00

720.

0005

0.00

010.

0000

AR

0.00

400.

0854

0.23

570.

1384

0.00

010.

0000

0.00

010.

0002

0.00

010.

0008

0.12

090.

0002

0.00

030.

0001

0.00

050.

0001

0.00

010.

0001

0.00

010.

1126

CH

0.00

020.

0605

0.13

570.

0178

0.00

010.

0001

0.00

010.

0002

0.00

010.

0388

0.07

520.

0002

0.00

020.

0000

0.00

020.

0001

0.00

010.

0000

0.00

010.

0673

GN

0.08

630.

0855

0.26

480.

0002

0.00

000.

0011

0.00

960.

0003

0.00

010.

2062

0.11

790.

0002

0.02

520.

0013

0.09

440.

0437

0.00

010.

0000

0.00

250.

1102

IYN

0.08

630.

0854

0.00

000.

0000

0.00

030.

0659

0.09

270.

0772

0.09

260.

0002

0.00

010.

0957

0.15

340.

1006

0.07

860.

0430

0.08

500.

1137

0.07

070.

0002

IYR

0.00

240.

0000

0.00

000.

0000

0.00

050.

0474

0.00

020.

0003

0.00

020.

0002

0.00

010.

0383

0.01

920.

0536

0.00

660.

0034

0.05

320.

0285

0.07

570.

0002

KG

0.08

620.

0000

0.00

000.

0000

0.00

030.

0478

0.07

620.

0333

0.05

160.

0010

0.00

010.

0606

0.00

020.

1006

0.03

290.

0838

0.06

340.

0002

0.09

170.

0002

KL

0.08

640.

0854

0.00

030.

0000

0.00

030.

0886

0.08

130.

0572

0.09

270.

0008

0.12

100.

0003

0.15

310.

0266

0.11

950.

0948

0.08

500.

1137

0.00

850.

1785

MR

0.00

010.

0000

0.00

000.

0000

0.00

030.

0665

0.08

120.

0927

0.04

230.

0002

0.00

000.

0894

0.00

020.

1008

0.00

090.

0947

0.06

380.

1102

0.06

360.

0002

MV

0.08

640.

0855

0.02

230.

0000

0.11

890.

0001

0.00

020.

0008

0.00

050.

0002

0.12

100.

0000

0.00

020.

0002

0.07

600.

0002

0.00

020.

0001

0.00

030.

0275

NH

0.08

640.

0854

0.02

200.

2354

0.11

260.

0001

0.00

080.

0001

0.03

270.

0001

0.11

610.

0000

0.00

380.

0001

0.05

420.

0001

0.00

010.

0001

0.00

010.

0000

NK

0.00

010.

0000

0.00

000.

0000

0.00

030.

0886

0.08

130.

0927

0.16

080.

0927

0.00

000.

0001

0.00

030.

1008

0.00

400.

0948

0.08

500.

0042

0.13

750.

0706

PLN

0.08

630.

0854

0.26

030.

2040

0.21

330.

0887

0.08

120.

0927

0.14

060.

0927

0.16

950.

1205

0.15

270.

0967

0.06

650.

0948

0.08

510.

1137

0.13

750.

2061

RY0.

0863

0.00

000.

0000

0.00

000.

0016

0.06

520.

0812

0.09

100.

0050

0.06

950.

0002

0.00

000.

0802

0.00

910.

0099

0.07

330.

0639

0.00

220.

1032

0.00

44SM

0.08

620.

0854

0.00

340.

0005

0.02

440.

0680

0.08

110.

0814

0.12

310.

0831

0.20

310.

1199

0.03

570.

0897

0.01

450.

0949

0.06

740.

0871

0.00

010.

2198

TV0.

0863

0.00

000.

0000

0.00

000.

0014

0.08

400.

0812

0.09

270.

0568

0.05

180.

0006

0.00

010.

0638

0.03

070.

1008

0.05

610.

0850

0.04

270.

1126

0.00

02VA

N0.

0864

0.08

540.

0000

0.00

000.

0549

0.08

860.

0650

0.09

270.

0761

0.09

260.

0002

0.00

070.

0869

0.15

340.

1008

0.07

600.

0524

0.11

370.

0581

0.00

02V

LR0.

0001

0.08

540.

0000

0.00

000.

0003

0.08

860.

0597

0.00

010.

0809

0.04

540.

0002

0.00

000.

0086

0.15

340.

0006

0.02

530.

0233

0.08

510.

0464

0.00

02Y

R0.

0001

0.00

000.

0000

0.00

000.

0008

0.08

860.

0812

0.09

270.

0201

0.09

210.

0002

0.00

000.

1024

0.02

890.

1008

0.02

960.

0948

0.08

510.

0701

0.00

13PA

0.00

020.

0854

0.26

470.

2356

0.27

400.

0002

0.00

010.

0235

0.04

020.

0699

0.19

370.

1202

0.11

560.

1158

0.00

010.

1775

0.02

440.

0002

0.08

560.

0003

Tota

l1.

0000

1.00

001.

0000

1.00

001.

0000

1.00

001.

0000

1.00

001.

0000

1.00

001.

0000

1.00

001.

0000

1.00

001.

0000

1.00

001.

0000

1.00

001.

0000

1.00

001.

0000

200 Journal of Genetics, Vol. 90, No. 2, August 2011

Genetic structure of Tamil Nadu ethnic groups

Figure 2. Neighbour-joining tree of 21 Tamil Nadu ethnic groups.Nomenclature of the NJ tree, A and B, ancestral and derived node;C and D, branch; C1, C2 and D1, subbranch; C1a, C1b, C2a andD1a, clade; C1a1, C1b1, C1b2, C2a1 and D1a1, subclade; C1a1.1,C1b1.1, C1b2.1 and D1b1.1, cluster; C1a1.11, subcluster.

of branch C than with branch D (table 4). Sengundar Mudaliar,a numerically large weavers community of Tamil Nadu (0.88million; Second Backward Class Commission 1989) clus-tered along with the early settlers (figure 1). They had greatergene flow with Parayan and equitable exchange with Kallar.They had no exchange with Agamudaiyar and Chakkiliyar.They exchanged with 18 ethnic groups and probably are anancient community.

Yadavar, a pan-Indian-pastoral community probably en-tered Tamil region about 10 kya from Mediterranean region(Wells et al. 2001) had no exchange with eight branch D eth-nic groups and two ethnic groups of branch C (Gavara Naiduand Nadar Hindu; table 4). Overall, Yadavar showed greateraffinity towards branch C ethnic groups. Vanniyar, an ethnicgroup equivalent to Kshatriyas of north India (Singh 1997)formed a close cluster with Yadavar of branch C (figure 1) hadexchanged with both branch C and D ethnic groups (table 4).

In conclusion, different ethnic group have entered Tamilspeaking region at different time periods. Chakkiliyar, Aga-mudaiyar and Ambalakarar with very high frequency of hap-logroup M, could be the oldest settlers. All ethnic groupswho possessed advanced knowledge of farming cluster in aseparate branch and are late arrived settlers to this region.The in situ populations have been created from ancient eth-nic groups at varied times as a result of interaction with theprevailing dominant socio-cultural force(s). The hierarchicalHindu caste system created many ethnic groups in the history

of its existence and some of them became isolated for con-siderable length of time. In spite of the rigidity in the castesystem, the built in flexibility allowed maternal gene flowbetween them.

Acknowledgements

This work was partly supported by a grant from Department ofBiotechnology, Govt. of India. We thank Prof. K N Poonuswamyand Prof. M R Srinivasan for their advice in statistical analysis.

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Received 15 January 2010, in final revised form 16 October 2010; accepted 7 December 2010Published on the Web: 19 August 2011

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