c Indian Academy of Sciences RESEARCH ARTICLE Genetic admixture studies on four in situ evolved, two migrant and 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 Pancreatic Diseases 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 Abstract We analysed the genetic structure of ∼1000 samples representing 27 ethnic groups settled in Tamil Nadu, south India, derived from 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, Labbai Muslim, Nadar Christian and south Indian Jain) and two are migrants (Gypsy and north Indian Jain) from north India to Tamil Nadu, 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, HincII13259 and 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 Tamil Nadu during different time periods. Genetic affinities and admixture estimates revealed that the ethnic groups possessing advanced knowledge of farming cluster in a branch (C), and could be the late arrived settlers as agriculture, was introduced to this region at about 5 to 3 thousand years ago. In situ ethnic groups appear to have arisen at various times as a result of the prevailing dominant socio-cultural forces. Hierarchical Hindu caste system created many ethnic groups in the history of its existence; some of them became isolated for considerable period of time. Over all, among Tamil ethnic groups, in spite of caste systems’ rigidity, built in flexibility in the system in the form of hypergamy and hypogamy had allowed maternal gene flow 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, two migrant and twenty-one ethnic populations of Tamil Nadu, south India. J. Genet. 90, 191–202] Introduction inhabitants of this state is expected to provide knowledge on some of the early inhabitants of India in general, and Tamil The contemporary populations of India are known to have Nadu in particular. evolved from peopling of India by waves of migrants from Several studies have been conducted on ethnic groups of time to time (Majumder 1998). Therefore, an intensive study Tamil Nadu that varied in the socio-cultural order, using of Indian populations provide deep knowledge about evo- somatoscopic, somatometric and genetic markers (Sanghvi lutionary forces that may be responsible for the diversity and Balakrishnan 1981), DNA markers (Wells et al. 2001; of contemporary Indian populations. The north Indian pop- Basu et al. 2003; Sitalaxmi et al. 2003; Rajkumar et al. 2004; ulations are predominantly Indo–European language speak- Kashyap et al. 2006; Kanthimathi et al. 2007; Vijaya et al. ers and south Indian populations are Dravidian speakers 2007) and HLA class II polymorphic markers (Pitchappan (Meenakshi 1995). Among these two linguistic groups, Dra- 2002). These studies revealed that many of them were mi- vidian language speakers are considered to be more ancient grants to Tamil Nadu from the neighbouring regions and that (Gadgil et al. 1998). Since Tamil Nadu in south India is the state harbours people who travelled by southern route from an ancient seat of Dravidian culture, focussed study on the Africa. The phylogenetic analysis placed them in a cluster, away from Indo–European speakers (Forster and Matsumura ∗ For correspondence. E-mail: [email protected]. 2005; Kanthimathi et al. 2007). Molecular evidence indicates Keywords. Dravidian; mitochondrial DNA; admixture; south India; human genetics. Journal of Genetics, Vol. 90, No. 2, August 2011 191 G. Suhasini et al. that mtDNA haplogroups M1 and M3 are found on the (ANI) and ancestral south Indian (ASI) gene pool. We have Horn of Africa, Arabia/Yemen, and Iran along a migration also tried to explain the same through our work. Histor- path to south India, which is congruent with anthropological, ically, hypogamy has not been encouraged. On the other linguistic and archaeological evidence and suggest African hand, in hypergamy women can adopt the caste and social origin for the Dravidian speakers (Winters 2008). Sanghvi status of the men whom they marry (Bhattacharyya et al. et al. (1981) even identified the ethnic groups of Tamil Nadu: 1999). Therefore, examining the female lineages could help Chakkiliyar, Parayan and Mutracha (Ambalakarar) as the in delineating the genetic structure of the ethnic groups most ancient who belong to the Paleolithic period. better. The genetic structure of the Tamil Nadu populations can To know the genetic structure (genomic affinities and be inferred from both matrilocal and patrilocal studies, as mi- interethnic admixture) of ethnic groups settled at various gration is gender based. Even though the caste system is rigid, time periods in Tamil Nadu, we analysed the maternal lin- two social rules viz., hypergamy or ‘Anuloma’ (a woman eage of 21 ethnic groups of this region and six more Tamil marrying a man of higher social rank) and hypogamy or ethnic groups studied by Basu et al. (2003) which could be ‘Pratiloma’ (a woman marrying a man of lower social sta- grouped variously based on religion, socio-economic rank- tus) provides flexibility to the rigid caste system. Reich ing in the caste hierarchical structure of the Hindu religion, et al. (2009) tried to point out the admixture in the Indian past traditional occupation, geographical origin and known population beyond the endogamy of ancestral north Indian in situ evolution (table 1). Table 1. Ethnological information on the study populations. Linguistic Categories Population name N Social strata group Traditional occupation/remarks A. Non-Hindu populations Migrant a) Jain North Indian Jain (NJ) 37 IE Trade/money lending/commerce In situ a) Jain South Indian Jain (SJ) 50 DR Agriculture/trade b) Christian Anglo-Indian (AI) 38 IE Urban dwellers Nadar Christian (NC) 46 DR Trade/agriculture/toddy tapping c) Muslim Labbai Muslim (ML) 50 DR Trade B. Hindu populations Migrant Gypsy (GP) 44 Low rank IE Seminomadic, denotified community, hunters, urban dwellers Brahmins Iyengar (IYN) 30 Upper rank DR Priests/scholars Iyer (IYR) 30 Upper rank DR Priests/scholars NonBrahmins a) Vellalar Agamudaiya Vellalar (AV) 47 Mid rank DR Agriculture Kongu Vellala Gounder (KG) 54 Mid rank DR Thuluva Vellalar (TV) 51 Mid rank DR Veerakodi 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 Agriculture Parayan (PA) 50 Low rank DR Agricultural labourer Common origin c) Thevar Agamudaiyar (AR) 47 Mid rank DR Agriculture Kallar (KL) 50 Mid rank DR Agriculture Maravar (MR) 45 Mid rank DR Agriculture d) Others Ambalakarar (AMB) 30 Mid rank DR Village heads Gavara Naidu (GN) 33 Mid rank DR Trade/agriculture Meenavar (MV) 68 Mid rank DR Fishermen (coastal) Nadar Hindu (NH) 51 Mid rank DR Agriculture/trade/toddy tapping Nattukkottai Chettiar (NK) 44 High rank DR Trade/commerce Reddiyar (RY) 49 Mid rank DR Agriculture Sengundar Mudaliar (SM) 50 Mid rank DR Weavers Vanniyar (VAN) 30 Mid rank DR Agriculture/trade Yadavar (YR) 51 Mid rank DR Animal husbandry/agriculture IE, Indo European; DR, Dravidian. 192 Journal of Genetics, Vol. 90, No. 2, August 2011 Genetic structure of Tamil Nadu ethnic groups Methods While estimating the admixture in in situ and migrant pop- ulations, these populations are considered as hybrid (Ph) and Populations the 21 ethnic groups as parental populations. Similarly, in A total of 1000 genomic DNA belonging to 21 ethnic groups case of estimating admixture in 21 ethnic groups, each time (three Indo–European language speaking groups: Anglo- one population among the 21 is considered to be hybrid and Indian, Gypsy and north Indian Jain; and 18 Tamil ethnic other 20 as parental population. groups: Muslim Labbai, south Indian Jain, Nattukkottai Chettiar, Sengundar Mudaliar, Agamudaiya Vellalar, Thuluva Vellalar, Yadavar, Kallar, Maravar, Agamudaiyar, Kongu Vellala Gounder, Nadar Hindu, Nadar Christian, Meenavar, Gavara Naidu, Reddiyar, Parayan and Chakkiliyar) were screened for mtDNA variations. Six more Tamil ethnic groups studied by Basu et al. (2003) were also included for phylogenetic and admixture analysis. These include: Iyer, Iyengar, Vanniyar, Ambalakarar, Veerakodi Vellalar and Pal- lan. A brief ethnographic information on all these ethnic groups is given in table 1. Genetic markers DNA samples were screened for 11 coding region variations Since there would be too many combinations, one popu- in mtDNA (HaeIII np 663, HpaI np 3592, AluI np 5176, AluI lation was always designated as common parental popula- np 7025, DdeI np 10394, AluI np 10397, HinfI np 12308, tion (P ). Thus, we have estimates of admixture proportions HincII np 13259, AluI np 13262, HaeIII np 16517 and 9- n for the n–1 populations. Individual admixture proportions of bp deletion; Torroni et al. 1993, 1996) to infer the gene these n–1 populations were pooled and a single estimate of flow between the Dravidians and contribution from different admixture proportion was estimated for the common parental groups of immigrants to Dravidians. population (Pn) paired with the remaining n–1 populations. Since for each pair of parental populations, p1 + p2 = 1, Statistical analysis the contribution for any hybrid population by n number of populations have to be adjusted to 1.