September 09, 2004

mtDNA in Iran and India

This article is a great survey of South and Southwest Asian mitochondrial diversity, showing a sharp difference between India and Iran, with the former having a high occurrence of "Proto-Asian" mtDNA types whose frequence falls drastically in Iran.

Indians have traditionally been characterized as being part of the periphery of the Caucasoid race. The subequatorial racial element which distinguishes Indians from Caucasoids-proper has been named Veddoid, Australoid or Palaeo-Indid by various researchers. These new genetic studies have shown Indians to be of mainly dual origins, with West Eurasian racial elements being added to a native South Asian base which persists more strongly in non-caste and southern populations of the subcontinent, and manifests itself primarily in Indian matrilineages.

BMC Genet. 2004 Aug 31;5(1):26.

Most of the extant mtDNA boundaries in South and Southwest Asia were likely shaped during the initial settlement of Eurasia by anatomically modern humans

Metspalu et al.

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.


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