title: Population differentiation of southern Indian male lineages correlates with agricultural expansions predating the caste system.
abstract: Previous studies that pooled Indian populations from a wide variety of geographical locations, have obtained contradictory conclusions about the processes of the establishment of the Varna caste system and its genetic impact on the origins and demographic histories of Indian populations. To further investigate these questions we took advantage that both Y chromosome and caste designation are paternally inherited, and genotyped 1,680 Y chromosomes representing 12 tribal and 19 non-tribal (caste) endogamous populations from the predominantly Dravidian-speaking Tamil Nadu state in the southernmost part of India. Tribes and castes were both characterized by an overwhelming proportion of putatively Indian autochthonous Y-chromosomal haplogroups (H-M69, F-M89, R1a1-M17, L1-M27, R2-M124, and C5-M356; 81% combined) with a shared genetic heritage dating back to the late Pleistocene (10-30 Kya), suggesting that more recent Holocene migrations from western Eurasia contributed <20% of the male lineages. We found strong evidence for genetic structure, associated primarily with the current mode of subsistence. Coalescence analysis suggested that the social stratification was established 4-6 Kya and there was little admixture during the last 3 Kya, implying a minimal genetic impact of the Varna (caste) system from the historically-documented Brahmin migrations into the area. In contrast, the overall Y-chromosomal patterns, the time depth of population diversifications and the period of differentiation were best explained by the emergence of agricultural technology in South Asia. These results highlight the utility of detailed local genetic studies within India, without prior assumptions about the importance of Varna rank status for population grouping, to obtain new insights into the relative influences of past demographic events for the population structure of the whole of modern India.
authors.affiliation: The Genographic Laboratory, School of Biological Sciences, Madurai Kamaraj University, Madurai, Tamil Nadu, India.
authors.forename: Ganeshprasad
authors.initials: G
authors.lastname: Arunkumar
authors.forename: David F
authors.initials: DF
authors.lastname: Soria-Hernanz
authors.forename: Valampuri John
authors.initials: VJ
authors.lastname: Kavitha
authors.forename: Varatharajan Santhakumari
authors.initials: VS
authors.lastname: Arun
authors.forename: Adhikarla
authors.initials: A
authors.lastname: Syama
authors.forename: Kumaran Samy
authors.initials: KS
authors.lastname: Ashokan
authors.forename: Kavandanpatti Thangaraj
authors.initials: KT
authors.lastname: Gandhirajan
authors.forename: Koothapuli
authors.initials: K
authors.lastname: Vijayakumar
authors.forename: Muthuswamy
authors.initials: M
authors.lastname: Narayanan
authors.forename: Mariakuttikan
authors.initials: M
authors.lastname: Jayalakshmi
authors.forename: Janet S
authors.initials: JS
authors.lastname: Ziegle
authors.forename: Ajay K
authors.initials: AK
authors.lastname: Royyuru
authors.forename: Laxmi
authors.initials: L
authors.lastname: Parida
authors.forename: R Spencer
authors.initials: RS
authors.lastname: Wells
authors.forename: Colin
authors.initials: C
authors.lastname: Renfrew
authors.forename: Theodore G
authors.initials: TG
authors.lastname: Schurr
authors.forename: Chris Tyler
authors.initials: CT
authors.lastname: Smith
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Platt
authors.forename: Ramasamy
authors.initials: R
authors.lastname: Pitchappan
mesh_terms: D000383:Agriculture; D041322:Chromosomes, Human, Y; D004272:DNA, Mitochondrial / Q000235:genetics; D003710:Demography; D005006:Ethnicity / Q000235:genetics; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D006239:Haplotypes; D063426:Human Migration; D006801:Humans; D007194:India / Q000208:ethnology; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics; D015233:Models, Statistical; D009154:Mutation; D010802:Phylogeny; D012923:Social Class
chemical_list: D004272:DNA, Mitochondrial