The geography of India has played a decisive role in the peopling of India. Populations within India have been subjected to foreign invasions and migrations from time to time, resulting in no single apparent origin for any present day population groups and a conglomeration of different Y-chromosomal lineages (Quintana-Murci et al 2001; Saha et al 2005). The maternal gene flow in and out of India has been limited since the initial settling of Indian maternal lineages (Metspalu et al 2004). Indian mtDNA lineages belong to either Asian-specific haplogroup M or western Eurasian-specific haplogroups H, I, J, K, U, W and others that were not established anywhere (Kivisild et al 1999). The high frequency and diversity of mtDNA haplogroup M, the major contributor to the Indian maternal gene pool, has been associated with its southwest-Asian origin (Roychoudhury et al 2000, 2001; Richards et al. 2003; Rajkumar et al. 2005), whereas the presence of lineage M1 in Africa (Quintana-Murci et al 1999) and lack of L3 lineages other than M and N in India has become the most parsimonious view of the origin of haplogroup M in east Africa, which has been supported by the most recent view of single rapid coastal settlement of Asia by three major mtDNA haplogroups, M, N and R (Palanichamy et al 2004; Macaulay et al 2005; Thangaraj et al 2005; Forster and Matsumura 2005) as the founding female lineages to Indian population groups. However, the restricted presence of M as M1 and the phylogeography of M1 in Africa, predominantly in the Afro-Asiatic linguistic phylum (Metspalu et al 2004), leaves the question of the origin of haplogroup M unanswered.
J Hum Genet. [Epub ahead of print]
Human mtDNA hypervariable regions, HVR I and II, hint at deep common maternal founder and subsequent maternal gene flow in Indian population groups.
S. Sharma et al.
We have analysed the hypervariable regions (HVR I and II) of human mitochondrial DNA (mtDNA) in individuals from Uttar Pradesh (UP), Bihar (BI) and Punjab (PUNJ), belonging to the Indo-European linguistic group, and from South India (SI), that have their linguistic roots in Dravidian language. Our analysis revealed the presence of known and novel mutations in both hypervariable regions in the studied population groups. Median joining network analyses based on mtDNA showed extensive overlap in mtDNA lineages despite the extensive cultural and linguistic diversity. MDS plot analysis based on Fst distances suggested increased maternal genetic proximity for the studied population groups compared with other world populations. Mismatch distribution curves, respective neighbour joining trees and other statistical analyses showed that there were significant expansions. The study revealed an ancient common ancestry for the studied population groups, most probably through common founder female lineage(s), and also indicated that human migrations occurred (maybe across and within the Indian subcontinent) even after the initial phase of female migration to India.