This one does not need any commentary.

Widely believed theory of Indo-Aryan invasion, often used to explain early settlements in the Indian subcontinent is a myth, a new study by Indian geneticists says. “Our study clearly shows that there was no genetic influx 3,500 years ago,” said Dr Kumarasamy Thangaraj of CCMB, who led the research team, which included scientists from the University of Tartu, Estonia, Chettinad Academy of Research and Education, Chennai and Banaras Hindu University. “It is high time we re-write India’s prehistory based on scientific evidence,” said Dr Lalji Singh, former director of CCMB. “There is no genetic evidence that Indo-Aryans invaded or migrated to India or even something such as Aryans existed”. Singh, vice-chancellor of BHU, is a coauthor.[Indians are not descendants of Aryans, says new study]

Here is a link to the paper.

Summing up, our results confirm both ancestry and temporal complexity shaping the still on-going process of genetic structuring of South Asian populations. This intricacy cannot be readily explained by the putative recent influx of Indo-Aryans alone but suggests multiple gene flows to the South Asian gene pool, both from the west and east, over a much longer time span. We highlight a few genes as candidates of positive selection in South Asia that could have implications in lipid metabolism and etiology of type 2 diabetes. Further studies on data sets without ascertainment and allele frequency biases such as sequence data will be needed to validate the signals for selection.

The point is that nothing exciting happened following the decline of the Harappan civilization. The Dravidian folklore is just that – folklore. Migrations did happen to the region, but they date to much earlier period before there were Dravidian and Indo-European languages.