Indo-Aryan or Indic peoples are an Indo-European ethno-linguistic group referring to the wide collection of peoples united as native speakers of the Indo-Aryan branch of the Indo-Iranian family of Indo-European languages. Today, there are over one billion native speakers of Indo-Aryan languages, most of them native to South Asia, where they form the majority.
The first people to have settled in India during Paleolithic times appear to have been an Australoid group who may have been closely related to Aboriginal Australians. From a genetic anthropological point of view, the research of Basu et al. (2003) indicates that: "(1) there is an underlying unity of female lineages in India, indicating that the initial number of female settlers may have been small; (2) the tribal and the caste populations are highly differentiated; (3) the Austro-Asiatic tribals are the earliest settlers in India, providing support to one anthropological hypothesis while refuting some others; (4) a major wave of humans entered India through the northeast; (5) the Tibeto-Burman tribals share considerable genetic commonalities with the Austro-Asiatic tribals, supporting the hypothesis that they may have shared a common habitat in southern China, but the two groups of tribals can be differentiated on the basis of Y-chromosomal haplotypes; (6) the Dravidian tribals were possibly widespread throughout India before the arrival of the Indo-European-speaking nomads, but retreated to southern India to avoid dominance; (7) formation of populations by fission that resulted in founder and drift effects have left their imprints on the genetic structures of contemporary populations; (8) the upper castes show closer genetic affinities with Central Asian populations, although those of southern India are more distant than those of northern India; (9) historical gene flow into India has contributed to a considerable obliteration of genetic histories of contemporary populations so that there is at present no clear congruence of genetic and geographical or sociocultural affinities."
The separation of Indo-Aryans proper from Indo-Iranians is commonly dated, on linguistic grounds, to roughly 1800 BCE. The Nuristani languages probably split in such early times, and are classified as either remote Indo-Aryan dialects or as an independent branch of Indo-Iranian. By the mid 2nd millennium BCE early Indo-Aryans had reached Assyria in the west (the Indo-Aryan superstrate in Mitanni) and the northern Punjab in the east (the Rigvedic tribes).