High-resolution mtDNA studies of the Indian population: Implications for palaeolithic settlement of the Indian subcontinent

The population of the Indian subcontinent represents a very complex social and cultural structure. Occupying a geographically central position for the early modern human migrations, indications are that the founder group that migrated out of East Africa also reached India. In the present study we used the twin strategy of mapping the whole mitochondrial DNA (mtDNA) using the standard 14 restriction enzymes, and sequencing the non-transcribed HVSI region, to derive maximum maternal lineages from a sample of non-tribal Indians. The essential features of the reduced median network of the two datasets were the same. Both showed two demographic expansions of two major haplogroups, 'M' and 'N'. The reduced median network was drawn with inputs from other studies on the Indian population, and correlated with data from other ethnic populations. The coalescence time of expansions and genetic diversity were estimated. A reduced median network was also drawn combining data from studies on Africans, Southeast Asians and West-Eurasians, tracing the migration of 'M' from East Africa to India. A time estimate of the migration of major mtDNA haplogroups from Africa was attempted. The comparison of a set of Indian maternal lineages belonging to different geographical regions of the country, with other populations revealed the in-situ differentiation and antiquity of the Indian population. Our analysis places the 'southern route' migration as the source of haplogroup 'M'. Multiple migrations might have brought the other major haplogroups, 'N' and 'R', found in our sample to India. Archaeological evidence of modern humans in the subcontinent supports this mtDNA study.