Shaffer (1993) refers to one set of data that undermines this simplistic portrayal of an apparent devolution and re-evolution of urbanization, which … - Jim G. Shaffer

This review of archaeological data demonstrates that a continued division of South Asian cultural history into discrete archaeological “cultures” or “sta­ges” such as non-Harappan, “early” Harappan, “mature” Harappan, Kot Dijian, “late” Harappan, Painted Gray Ware and others masks the existence of a long surviving cultural tradition, and distorts the processes responsible for the cultu­ral changes this variety of designations represents. Archaeological data indicate the existence of a long-term cultural tradition responsive to changing cultural and ecological contexts, with an ability to adjust to rapid, as well as long-term, changes.

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.

[the demographic eastward shift of the Harappan population during the decline of their cities, i.e. an intra-Indian movement from Indus to Ganga,] “is the only archaeologically documented west-to-east movement of human populations in South Asia before the first half of the first millennium BC”, while the archaeological record shows “no significant discontinuities” for the period when the Aryan invasion should have made its mark.