4 research outputs found
Genetic Evidence on the Origins of Indian Caste Populations
This is the published version, also available here: http://www.dx.doi.org/10.1101/gr.173301.The origins and affinities of the ∼1 billion people living on the subcontinent of India have long been contested.
This is owing, in part, to the many different waves of immigrants that have influenced the genetic structure of
India. In the most recent of these waves, Indo-European-speaking people from West Eurasia entered India from
the Northwest and diffused throughout the subcontinent. They purportedly admixed with or displaced
indigenous Dravidic-speaking populations. Subsequently they may have established the Hindu caste system and
placed themselves primarily in castes of higher rank. To explore the impact of West Eurasians on contemporary
Indian caste populations, we compared mtDNA (400 bp of hypervariable region 1 and 14 restriction site
polymorphisms) and Y-chromosome (20 biallelic polymorphisms and 5 short tandem repeats) variation in ∼265
males from eight castes of different rank to ∼750 Africans, Asians, Europeans, and other Indians. For maternally
inherited mtDNA, each caste is most similar to Asians. However, 20%–30% of Indian mtDNA haplotypes
belong to West Eurasian haplogroups, and the frequency of these haplotypes is proportional to caste rank, the
highest frequency of West Eurasian haplotypes being found in the upper castes. In contrast, for paternally
inherited Y-chromosome variation each caste is more similar to Europeans than to Asians. Moreover, the
affinity to Europeans is proportionate to caste rank, the upper castes being most similar to Europeans,
particularly East Europeans. These findings are consistent with greater West Eurasian male admixture with castes
of higher rank. Nevertheless, the mitochondrial genome and the Y chromosome each represents only a single
haploid locus and is more susceptible to large stochastic variation, bottlenecks, and selective sweeps. Thus, to
increase the power of our analysis, we assayed 40 independent, biparentally inherited autosomal loci (1 LINE-1
and 39 Alu elements) in all of the caste and continental populations (∼600 individuals). Analysis of these data
demonstrated that the upper castes have a higher affinity to Europeans than to Asians, and the upper castes are
significantly more similar to Europeans than are the lower castes. Collectively, all five datasets show a trend
toward upper castes being more similar to Europeans, whereas lower castes are more similar to Asians. We
conclude that Indian castes are most likely to be of proto-Asian origin with West Eurasian admixture resulting
in rank-related and sex-specific differences in the genetic affinities of castes to Asians and Europeans
Mitochondrial DNA Variation in Nicobarese Islanders
The aboriginal populations living in the Nicobar Islands are hypothesized to be descendants of people who were part of early human dispersals into Southeast Asia. However, analyses of ethnographic histories, languages, morphometric data, and protein polymorphisms have not yet resolved which worldwide populations are most closely related to the Nicobarese. Thus, to explore the origins and affinities of the Nicobar Islanders, we analyzed mitochondrial DNA (mtDNA) hypervariable region 1 sequence data from 33 Nicobarese Islanders and compared their mtDNA haplotypes to those of neighboring East Asians, mainland and island Southeast Asians, Indians, Australian aborigines, Pacific Islanders, and Africans. Unique Nicobarese mtDNA haplotypes, including five Nicobarese mtDNA haplotypes linked to the COII/tRNALys 9-bp deletion, are most closely related to mtDNA haplotypes from mainland Southeast Asian Mon-Kmer-speaking populations (e.g., Cambodians). Thus, the dispersal of southern Chinese into mainland Southeast Asia may have included a westward expansion and colonization of the islands of the Andaman Sea
Genetic Evidence on the Origins of Indian Caste Populations
The origins and affinities of the ∼1 billion people living on the subcontinent of India have long been contested. This is owing, in part, to the many different waves of immigrants that have influenced the genetic structure of India. In the most recent of these waves, Indo-European-speaking people from West Eurasia entered India from the Northwest and diffused throughout the subcontinent. They purportedly admixed with or displaced indigenous Dravidic-speaking populations. Subsequently they may have established the Hindu caste system and placed themselves primarily in castes of higher rank. To explore the impact of West Eurasians on contemporary Indian caste populations, we compared mtDNA (400 bp of hypervariable region 1 and 14 restriction site polymorphisms) and Y-chromosome (20 biallelic polymorphisms and 5 short tandem repeats) variation in ∼265 males from eight castes of different rank to ∼750 Africans, Asians, Europeans, and other Indians. For maternally inherited mtDNA, each caste is most similar to Asians. However, 20%–30% of Indian mtDNA haplotypes belong to West Eurasian haplogroups, and the frequency of these haplotypes is proportional to caste rank, the highest frequency of West Eurasian haplotypes being found in the upper castes. In contrast, for paternally inherited Y-chromosome variation each caste is more similar to Europeans than to Asians. Moreover, the affinity to Europeans is proportionate to caste rank, the upper castes being most similar to Europeans, particularly East Europeans. These findings are consistent with greater West Eurasian male admixture with castes of higher rank. Nevertheless, the mitochondrial genome and the Y chromosome each represents only a single haploid locus and is more susceptible to large stochastic variation, bottlenecks, and selective sweeps. Thus, to increase the power of our analysis, we assayed 40 independent, biparentally inherited autosomal loci (1 LINE-1 and 39 Alu elements) in all of the caste and continental populations (∼600 individuals). Analysis of these data demonstrated that the upper castes have a higher affinity to Europeans than to Asians, and the upper castes are significantly more similar to Europeans than are the lower castes. Collectively, all five datasets show a trend toward upper castes being more similar to Europeans, whereas lower castes are more similar to Asians. We conclude that Indian castes are most likely to be of proto-Asian origin with West Eurasian admixture resulting in rank-related and sex-specific differences in the genetic affinities of castes to Asians and Europeans