Indian tribal mtDNA landscape

Gene Expression
By Razib Khan
Oct 13, 2009 3:16 PMNov 5, 2019 9:41 AM


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A new paper adding some decimal places on Indian mtDNA phylogeography, Updating Phylogeny of Mitochondrial DNA Macrohaplogroup M in India: Dispersal of Modern Human in South Asian Corridor:

To construct maternal phylogeny and prehistoric dispersals of modern human being in the Indian sub continent, a diverse subset of 641 complete mitochondrial DNA (mtDNA) genomes belonging to macrohaplogroup M was chosen from a total collection of 2,783 control-region sequences, sampled from 26 selected tribal populations of India. On the basis of complete mtDNA sequencing, we identified 12 new haplogroups - M53 to M64; redefined/ascertained and characterized haplogroups M2, M3, M4, M5, M6, M8′C′Z, M9, M10, M11, M12-G, D, M18, M30, M33, M35, M37, M38, M39, M40, M41, M43, M45 and M49, which were previously described by control and/or coding-region polymorphisms. Our results indicate that the mtDNA lineages reported in the present study (except East Asian lineages M8′C′Z, M9, M10, M11, M12-G, D ) are restricted to Indian region.The deep rooted lineages of macrohaplogroup 'M' suggest in-situ origin of these haplogroups in India. Most of these deep rooting lineages are represented by multiple ethnic/linguist groups of India. Hierarchical analysis of molecular variation (AMOVA) shows substantial subdivisions among the tribes of India (FST = 0.16164). The current Indian mtDNA gene pool was shaped by the initial settlers and was galvanized by minor events of gene flow from the east and west to the restricted zones. Northeast Indian mtDNA pool harbors region specific lineages, other Indian lineages and East Asian lineages. We also suggest the establishment of an East Asian gene in North East India through admixture rather than replacement.

These mtDNA (maternal lineage) papers always show deep and ancient roots for the heritage of South Asians. As a contrast, it looks like the majority, though not the totality, of Japanese genetic heritage can be traced to the migration of rice farmers from mainland East Asia ~2,000 years ago. Their subsequent population explosion on the islands of Japan at the expense of the indigenous Jomon and post-Jomon groups (the Ainu being a relict of these) created the human geography which we're familiar with today. In contrast, India is often described by papers with titles such as The genetic heritage of the earliest settlers persists both in Indian tribal and caste populations. The "earliest" meaning before the end of the Ice Age, the populations who arrived circa 50,000 or more years ago Out of Africa. And yet David Reich's recent paper on Indian genetics suggests that the populations of South Asia have a component which is far closer to Europeans than that of the earliest settlers (i.e., the relatives of the Andaman Islanders), and that that component is predominant in most though not all Indian populations (as in the, the majority component). Is it plausible that this European-like component was present in northwest India for tens of thousands of years, engaging in gene flow with Europeans, but not with Indian populations to the south and east? If this population is exogenous, is it plausible that it is due to the Indo-Aryan migration which most archaeologists and philologists date between 4 and 3 thousand years ago? If this is plausible, why is it that the low bound for the European-like component in tribal populations is 40%? Was there that much gene-flow between tribal groups outside of the mainstream of Indian society and Indo-Aryan groups in the past 3,000 years? Even in South India where the Indo-Aryan languages did not replace indigenous languages? And can it be that this predominant European-like component was nearly totally male-mediated in its genetic impact? There's a lot that doesn't compute for me. The data I put more stock in than the models which explain the data. Citation: Chandrasekar A, Kumar S, Sreenath J, Sarkar BN, Urade BP, et al. 2009 Updating Phylogeny of Mitochondrial DNA Macrohaplogroup M in India: Dispersal of Modern Human in South Asian Corridor. PLoS ONE 4(10): e7447. doi:10.1371/journal.pone.0007447

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