The Indian Subcontinent is the genetically most diverse area in the world outside of Africa, implying an early settlement and maintenance of a relatively large population size not long after the exodus of a small founder group of humans from Africa around fifty thousand years ago (Chaubey et al. 2008). The time taken for this group to migrate from Africa to India and then on to Australia has been estimated genetically at less than fifty-three hundred years (Hudjashov et al. 2007). In a study based on mtDNA analysis, the team of Kivisild and colleagues (Metspalu et al. 2004) describes a package of the three most ancient mtDNA branches, which are specific to and widespread within the Indian Subcontinent: mtDNA branches M2, R5 and U2i. These three branches are between fifty thousand and seventy thousand years old and evidently represent the first successful Anatomically Modern Human settlers on the Indian Subcontinent. The corresponding ancient Indian Y chromosome lineages may include types within the branches C5, H, F, L1 and R2, postulated to be the minimal set to be indigenous to India (Sengupta et al. 2006), which together constitute about a quarter of Indian Y-types.
A possibly different interpretation is offered by Reich and colleagues (2009), who analysed autosomal DNA in twenty-five diverse Indian samples and grouped them phylogenetically by assuming the controversial concept of “fissioning populations”. The concept of population fissions is problematic in cases of long periods where apparently discrete populations of humans can partly or wholly merge at some point in prehistory, confounding the analysis. Bearing this caveat in mind, it is nevertheless interesting that these authors conclude that Indian genetic variation consists of two ancient components, one of which is an “Ancestral South Indian” component whose descendant alleles are found mainly in southern Indians but found in pure form only in the Andaman islanders.