An Indian Ancestry: a Key for Understanding Human Diversity in Europe and Beyond
A recent African origin of modern humans, although still disputed, is supported now by a majority of genetic studies. To address the question when and where very early diversification(s) of modern humans outside of Africa occurred, we concentrated on the investigation of maternal and paternal lineages of the extant populations of India, southern China, Caucasus, Anatolia and Europe. Through the analyses of about 1000 mtDNA genomes and 400 Y chromosomesfrom various locations in India we reached the following conclusions, relevant to the peopling of Europe in particular and of the Old World in general. First, we found that the node of the phylogenetic tree of mtDNA, ancestral to more than 90 per cent of the present-day typically European maternal lineages, is present in India at a relatively high frequency. Inferred coalescence time of this ancestral node is slightly above 50,000 BP. Second, we found that haplogroup U is the second most abundant mtDNA variety in India as it is in Europe. Summing up, we believe that there are now enough reasons not only to question a 'recent Indo-Aryan invasion' into India some 4000 BP, but alternatively to consider India as a part of the common gene pool ancestral to the diversity of human maternal lineages in Europe. Our results on Y-chromosomal diversity of various Indian populations support an early split between Indian and east of Indian paternal lineages, while on a surface, Indian (Sanskrit as well as Dravidic speakers) and European Y-chromosomal lineages are much closer than the corresponding mtDNA variants.
PDF file
Influence of language and ancestry on genetic structure of contiguous populations: A microsatellite based study on populations of Orissa
Background: We have examined genetic diversity at fifteen autosomal microsatellite loci in seven predominant populations of Orissa to decipher whether populations inhabiting the same geographic region can be differentiated on the basis of language or ancestry. The studied populations have diverse historical accounts of their origin, belong to two major ethnic groups and different linguistic families. Caucasoid caste populations are speakers of Indo-European language and comprise Brahmins, Khandayat, Karan and Gope, while the three Australoid tribal populations include two Austric speakers: Juang and Saora and a Dravidian speaking population, Paroja. These divergent groups provide a varied substratum for understanding variation of genetic patterns in a geographical area resulting from differential admixture between migrants groups and aboriginals, and the influence of this admixture on population stratification.
Results: The allele distribution pattern showed uniformity in the studied groups with approximately 81% genetic variability within populations. The coefficient of gene differentiation was found to be significantly higher in tribes (0.014) than caste groups (0.004). Genetic variance between the groups was 0.34% in both ethnic and linguistic clusters and statistically significant only in the ethnic apportionment. Although the populations were genetically close (FST = 0.010), the contemporary caste and tribal groups formed distinct clusters in both Principal-Component plot and Neighbor-Joining tree. In the phylogenetic tree, the Orissa Brahmins showed close affinity to populations of North India, while Khandayat and Gope clustered with the tribal groups, suggesting a possibility of their origin from indigenous people.
Conclusions: The extent of genetic differentiation in the contemporary caste and tribal groups of Orissa is highly significant and constitutes two distinct genetic clusters. Based on our observations, we suggest that since genetic distances and coefficient of gene differentiation were fairly small, the studied populations are indeed genetically similar and that the genetic structure of populations in a geographical region is primarily influenced by their ancestry and not by socio-cultural hierarchy or language. The scenario of genetic structure, however, might be different for other regions of the subcontinent where populations have more similar ethnic and linguistic backgrounds and there might be variations in the patterns of genomic and socio-cultural affinities in different geographical regions.
PDF file
Molecular insight into the genesis of ranked caste populations of western India based upon polymorphisms across nonrecombinant and recombinant regions in genome
Background
Large-scale trade and cultural contacts between coastal populations of western India and Western-Eurasians paved for extensive immigration and genesis of wide spectrum of admixed gene pool. To trace admixture and genesis of caste populations of western India, we have examined polymorphisms across non-recombining 20 Y-SNPs, 20 Y-STRs, 18 mtDNA diagnostic sites, HVS-1 plus HVS-2 regions; and recombining 15 highly polymorphic autosomal STRs in four predominant caste populations- upper-ranking Desasth-brahmin and Chitpavan-brahmin; a middle-ranking Kshtriya Maratha; and a lower-rank peasant Dhangar.
Results
The generated genomic data was compared with putative parental populations- Central Asians, West Asians and Europeans using AMOVA, PC plot, and admixture estimates. Overall, disparate uniparental ancestries, and l.1% GST value for biparental markers among four studied caste populations linked well with their exchequer demographic histories. Marathi-speaking ancient Desasth-brahmin shows substantial admixture from Central Asian males but Paleolithic maternal component support their Scytho-Dravidian origin. Chitpavanbrahmin demonstrates younger maternal component and substantial paternal gene flow from West Asia, thus giving credence to their recent Irano-Scythian ancestry from Mediterranean or Turkey, which correlated well with European-looking features of this caste. This also explains their untraceable ethno-history before 1000 years, brahminization event and later amalgamation by Maratha. The widespread Palaeolithic mtDNA haplogroups in Maratha and Dhangar highlight their shared Proto-Asian ancestries. Maratha males harboured Anatolian-derived J2 lineage corroborating the blending of farming communities. Dhangar heterogeneity is ascribable to predominantly South-Asian males and West-Eurasian females.
Conclusions
The genomic data-sets of this study provide ample genomic evidences of diverse origins of four ranked castes and synchronization of caste stratification with asymmetrical gene flows from Indo-European migration during Upper Paleolithic, Neolithic, and later dates. However, subsequent gene flows among these castes living in geographical proximity, have diminished significant genetic differentiation as indicated by AMOVA and structure.
PDF file
Genetic affinities among the lower castes and tribal groups of India: inference from Y chromosome and mitochondrial DNA
Background:
India is a country with enormous social and cultural diversity due to its positioning on the crossroads of many historic and pre-historic human migrations. The hierarchical caste system in the Hindu society dominates the social structure of the Indian populations. The origin of the caste system in India is a matter of debate with many linguists and anthropologists suggesting that it began with the arrival of Indo-European speakers from Central Asia about 3500 years ago. Previous genetic studies based on Indian populations failed to achieve a consensus in this regard. We analysed the Y-chromosome and mitochondrial DNA of three tribal populations of southern India, compared the results with available data from the Indian subcontinent and tried to reconstruct the evolutionary history of Indian caste and tribal populations.
Results:
No significant difference was observed in the mitochondrial DNA between Indian tribal and caste populations, except for the presence of a higher frequency of west Eurasian-specific haplogroups in the higher castes, mostly in the north western part of India. On the other hand, the study of the Indian Y lineages revealed distinct distribution patterns among caste and tribal populations. The paternal lineages of Indian lower castes showed significantly closer affinity to the tribal populations than to the upper castes. The frequencies of deep-rooted Y haplogroups such as M89, M52, and M95 were higher in the lower castes and tribes, compared to the upper castes.
Conclusion:
The present study suggests that the vast majority (>98%) of the Indian maternal gene pool, consisting of Indio-European and Dravidian speakers, is genetically more or less uniform. Invasions after the late Pleistocene settlement might have been mostly male-mediated. However, Y-SNP data provides compelling genetic evidence for a tribal origin of the lower caste populations in the subcontinent. Lower caste groups might have originated with the hierarchical divisions that arose within the tribal groups with the spread of Neolithic agriculturalists, much earlier than the arrival of Aryan speakers. The Indo-Europeans established themselves as upper castes among this already developed caste-like class structure within the tribes.
PDF file
A recent African origin of modern humans, although still disputed, is supported now by a majority of genetic studies. To address the question when and where very early diversification(s) of modern humans outside of Africa occurred, we concentrated on the investigation of maternal and paternal lineages of the extant populations of India, southern China, Caucasus, Anatolia and Europe. Through the analyses of about 1000 mtDNA genomes and 400 Y chromosomesfrom various locations in India we reached the following conclusions, relevant to the peopling of Europe in particular and of the Old World in general. First, we found that the node of the phylogenetic tree of mtDNA, ancestral to more than 90 per cent of the present-day typically European maternal lineages, is present in India at a relatively high frequency. Inferred coalescence time of this ancestral node is slightly above 50,000 BP. Second, we found that haplogroup U is the second most abundant mtDNA variety in India as it is in Europe. Summing up, we believe that there are now enough reasons not only to question a 'recent Indo-Aryan invasion' into India some 4000 BP, but alternatively to consider India as a part of the common gene pool ancestral to the diversity of human maternal lineages in Europe. Our results on Y-chromosomal diversity of various Indian populations support an early split between Indian and east of Indian paternal lineages, while on a surface, Indian (Sanskrit as well as Dravidic speakers) and European Y-chromosomal lineages are much closer than the corresponding mtDNA variants.
PDF file
Influence of language and ancestry on genetic structure of contiguous populations: A microsatellite based study on populations of Orissa
Background: We have examined genetic diversity at fifteen autosomal microsatellite loci in seven predominant populations of Orissa to decipher whether populations inhabiting the same geographic region can be differentiated on the basis of language or ancestry. The studied populations have diverse historical accounts of their origin, belong to two major ethnic groups and different linguistic families. Caucasoid caste populations are speakers of Indo-European language and comprise Brahmins, Khandayat, Karan and Gope, while the three Australoid tribal populations include two Austric speakers: Juang and Saora and a Dravidian speaking population, Paroja. These divergent groups provide a varied substratum for understanding variation of genetic patterns in a geographical area resulting from differential admixture between migrants groups and aboriginals, and the influence of this admixture on population stratification.
Results: The allele distribution pattern showed uniformity in the studied groups with approximately 81% genetic variability within populations. The coefficient of gene differentiation was found to be significantly higher in tribes (0.014) than caste groups (0.004). Genetic variance between the groups was 0.34% in both ethnic and linguistic clusters and statistically significant only in the ethnic apportionment. Although the populations were genetically close (FST = 0.010), the contemporary caste and tribal groups formed distinct clusters in both Principal-Component plot and Neighbor-Joining tree. In the phylogenetic tree, the Orissa Brahmins showed close affinity to populations of North India, while Khandayat and Gope clustered with the tribal groups, suggesting a possibility of their origin from indigenous people.
Conclusions: The extent of genetic differentiation in the contemporary caste and tribal groups of Orissa is highly significant and constitutes two distinct genetic clusters. Based on our observations, we suggest that since genetic distances and coefficient of gene differentiation were fairly small, the studied populations are indeed genetically similar and that the genetic structure of populations in a geographical region is primarily influenced by their ancestry and not by socio-cultural hierarchy or language. The scenario of genetic structure, however, might be different for other regions of the subcontinent where populations have more similar ethnic and linguistic backgrounds and there might be variations in the patterns of genomic and socio-cultural affinities in different geographical regions.
PDF file
Molecular insight into the genesis of ranked caste populations of western India based upon polymorphisms across nonrecombinant and recombinant regions in genome
Background
Large-scale trade and cultural contacts between coastal populations of western India and Western-Eurasians paved for extensive immigration and genesis of wide spectrum of admixed gene pool. To trace admixture and genesis of caste populations of western India, we have examined polymorphisms across non-recombining 20 Y-SNPs, 20 Y-STRs, 18 mtDNA diagnostic sites, HVS-1 plus HVS-2 regions; and recombining 15 highly polymorphic autosomal STRs in four predominant caste populations- upper-ranking Desasth-brahmin and Chitpavan-brahmin; a middle-ranking Kshtriya Maratha; and a lower-rank peasant Dhangar.
Results
The generated genomic data was compared with putative parental populations- Central Asians, West Asians and Europeans using AMOVA, PC plot, and admixture estimates. Overall, disparate uniparental ancestries, and l.1% GST value for biparental markers among four studied caste populations linked well with their exchequer demographic histories. Marathi-speaking ancient Desasth-brahmin shows substantial admixture from Central Asian males but Paleolithic maternal component support their Scytho-Dravidian origin. Chitpavanbrahmin demonstrates younger maternal component and substantial paternal gene flow from West Asia, thus giving credence to their recent Irano-Scythian ancestry from Mediterranean or Turkey, which correlated well with European-looking features of this caste. This also explains their untraceable ethno-history before 1000 years, brahminization event and later amalgamation by Maratha. The widespread Palaeolithic mtDNA haplogroups in Maratha and Dhangar highlight their shared Proto-Asian ancestries. Maratha males harboured Anatolian-derived J2 lineage corroborating the blending of farming communities. Dhangar heterogeneity is ascribable to predominantly South-Asian males and West-Eurasian females.
Conclusions
The genomic data-sets of this study provide ample genomic evidences of diverse origins of four ranked castes and synchronization of caste stratification with asymmetrical gene flows from Indo-European migration during Upper Paleolithic, Neolithic, and later dates. However, subsequent gene flows among these castes living in geographical proximity, have diminished significant genetic differentiation as indicated by AMOVA and structure.
PDF file
Genetic affinities among the lower castes and tribal groups of India: inference from Y chromosome and mitochondrial DNA
Background:
India is a country with enormous social and cultural diversity due to its positioning on the crossroads of many historic and pre-historic human migrations. The hierarchical caste system in the Hindu society dominates the social structure of the Indian populations. The origin of the caste system in India is a matter of debate with many linguists and anthropologists suggesting that it began with the arrival of Indo-European speakers from Central Asia about 3500 years ago. Previous genetic studies based on Indian populations failed to achieve a consensus in this regard. We analysed the Y-chromosome and mitochondrial DNA of three tribal populations of southern India, compared the results with available data from the Indian subcontinent and tried to reconstruct the evolutionary history of Indian caste and tribal populations.
Results:
No significant difference was observed in the mitochondrial DNA between Indian tribal and caste populations, except for the presence of a higher frequency of west Eurasian-specific haplogroups in the higher castes, mostly in the north western part of India. On the other hand, the study of the Indian Y lineages revealed distinct distribution patterns among caste and tribal populations. The paternal lineages of Indian lower castes showed significantly closer affinity to the tribal populations than to the upper castes. The frequencies of deep-rooted Y haplogroups such as M89, M52, and M95 were higher in the lower castes and tribes, compared to the upper castes.
Conclusion:
The present study suggests that the vast majority (>98%) of the Indian maternal gene pool, consisting of Indio-European and Dravidian speakers, is genetically more or less uniform. Invasions after the late Pleistocene settlement might have been mostly male-mediated. However, Y-SNP data provides compelling genetic evidence for a tribal origin of the lower caste populations in the subcontinent. Lower caste groups might have originated with the hierarchical divisions that arose within the tribal groups with the spread of Neolithic agriculturalists, much earlier than the arrival of Aryan speakers. The Indo-Europeans established themselves as upper castes among this already developed caste-like class structure within the tribes.
PDF file
