Nineteenth century philologists (Bowler 1989; Ölender 1992; Poliakov 1974; Shaffer 1984) also invoked invasion as a primary explanation for ling­uist… - Jim G. Shaffer

The shift by Harappan groups, and perhaps, other Indus Valley cultural mosaic groups, is the only archaeologically documented west-to-east movement of human populations in South Asia before the first half of the first millennium BC.

The archaeological record and ancient oral and literate traditions of South Asia are now converging with significant implications for South Asian cultural history. Some scholars suggest there is nothing in the “literature” firmly locating Indo-Aryans, the generally perceived founders of modern South Asian cultural tradition(s) outside of South Asia, and the archaeological record is now confirming this. Within the chronology of the archaeological data for South Asia describing cultural continuity, however, a significant indigenous discontinuity occurs, but it is one correlated to significant geological and environmental changes in the prehistoric period. This indigenous discontinuity was a regional population shift from the Indus Valley area to locations east, that is, Gangetic Valley, and to the southeast, that is, Gujarat and beyond. Such an indigenous population movement can be recorded in the ancient oral Vedic traditions as perhaps “the” migration so focused upon in the linguistic reconstructions of a prehistoric chronology for South Asia.

In both instances, the Indo-Aryan concept was never subjected to rigorous validation beyond the field of historical linguistics. Linguistic reconstructions were used to interpret archaeological materials, which in tum were used to substantiate the original cultural reconstructions. It was not until the mid-20th century that archaeological data were independently used to examine the validity of the Indo-Aryan concept.