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Background: Recent advances in the understanding of the maternal and paternal heritage of south and southwest Asian populations have highlighted their role in the colonization of Eurasia by anatomically modern humans. Further understanding requires a deeper insight into the topology of the branches of the Indian mtDNA phylogenetic tree, which should be contextualized within the phylogeography of the neighboring regional mtDNA variation. Accordingly, we have analyzed mtDNA control and coding region variation in 796 Indian (including both tribal and caste populations from different parts of India) and 436 Iranian mtDNAs. The results were integrated and analyzed together with published data from South, Southeast Asia and West Eurasia. Results: Four new Indian-specific haplogroup M sub-clades were defined. These, in combination with two previously described haplogroups, encompass approximately one third of the haplogroup M mtDNAs in India. Their phylogeography and spread among different linguistic phyla and social strata was investigated in detail. Furthermore, the analysis of the Iranian mtDNA pool revealed patterns of limited reciprocal gene flow between Iran and the Indian sub-continent and allowed the identification of different assemblies of shared mtDNA sub-clades. Conclusions: Since the initial peopling of South and West Asia by anatomically modern humans, when this region may well have provided the initial settlers who colonized much of the rest of Eurasia, the gene flow in and out of India of the maternally transmitted mtDNA has been surprisingly limited. Specifically, our analysis of the mtDNA haplogroups, which are shared between Indian and Iranian populations and exhibit coalescence ages corresponding to around the early Upper Paleolithic, indicates that they are present in India largely as Indian-specific sub-lineages. In contrast, other ancient Indian-specific variants of M and R are very rare outside the sub-continent. [ABSTRACT FROM AUTHOR]

We determine the phylogenetic backbone of the East Asian mtDNA tree by using published complete mtDNA sequences and assessing both coding and control region variation in 69 Han individuals from southern China. This approach assists in the interpretation of published mtDNA data on East Asians based on either control region sequencing or restriction fragment length polymorphism (RFLP) typing. Our results confirm that the East Asian mtDNA pool is locally region-specific and completely covered by the two superhaplogroups M and N. The phylogenetic partitioning based on complete mtDNA sequences corroborates existing RFLP-based classification of Asian mtDNA types and supports the distinction between northern and southern populations. We describe new haplogroups M7, M8, M9, N9, and R9 and demonstrate by way of example that hierarchically subdividing the major branches of the mtDNA tree aids in recognizing the settlement processes of any particular region in appropriate time scale. This is illustrated by the characteristically southern distribution of haplogroup M7 in East Asia, whereas its daughter-groups, M7a and M7b2, specific for Japanese and Korean populations, testify to a presumably (pre-)Jomon contribution to the modern mtDNA pool of Japan. [ABSTRACT FROM PUBLISHER]

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