Fundamental genomic unity of ethnic India is revealed by analysis of mitochondrial DNA

Mitochondrial DNA (mtDNA) profiles of 23 ethnic populations of India drawn from diverse cultural, linguistic and geographical backgrounds are presente d. There is extensive sharing of a small number of mtDNA haplotypes, recons tructed on the basis of restriction fragment length polymorphisms, among th e populations. This indicates that Indian populations were founded by a sma ll number of females, possibly arriving on one of the early waves of out-of -Africa migration of modern humans; ethnic differentiation occurred subsequ ently through demographic expansions and geographic dispersal, The Asian-sp ecific haplogroup M is in high frequency in most populations, especially tr ibal populations and Dravidian populations of southern India, Populations i n which the frequencies of haplogroup M are relatively lo M ef show higher frequencies of haplogroup U; such populations are primarily caste populatio ns of northern India. This finding is indicative of a higher Caucasoid admi xture in northern Indian populations. By examining the sharing of haplotype s between Indian and south-east Asian populations, we have provided evidenc e that south-east Asia was peopled by two waves of migration, one originati ng in India and the other originating in southern China. These findings hav e been examined and interpreted in the light of inferences derived from pre vious genomic and historical studies.