Recently read articles such as this. How much do these findings change the current accepted theories and what even are the current, accepted theories? In India, all I see is that proponents of both origin theories are more interested in the politics rather than truth and discovery, using their preferred theory to sell their brand of politics.
Well, what I can say is that genetics certainly backs the Indo-European migrations, and the introduction of Indo-Aryan languages in the Indian subcontinent coincides with the arrival of a influx of West Eurasian genes (ANI) into a mixed West Eurasian/East Eurasian population (ASI), the former being associated with Indo-Aryan speakers, the latter with Dravidian speakers, although their is a large transition between the two and a large number of exceptions, as many Marathi speakers who speak an Indo-Aryan language mostly resemble the Dravidian speakers neighboring them or Brahui speakers in Pakistan who speak a Dravudian language resemble the Indo-Aryan groups like the Baloch that they live amongst. An 'Out-of-India' origin of the Indo-European languages is fringe and unsupported by data, as we would see a much larger expanse of the ASI component away from the Indian subcontinent. The Yamnaya (proto-Indo-Europeans) did not carry ASI for the most part, yet their genetic components are present in almost every Indo-European seaking group, including those of the Indian subcontinent.
The Indus Valley was founded either by an early or ancestral Dravidian population, or a closely related group. However, it is clear that the Indus Valley itself was a bridge of more western and eastern cultures, as reflected in the genetic makeup of the population who were heavily admixed with an earlier pre-Indo-European West Eurasian migrant population, founding the mixed ASI - Ancestral South Indian - component. However, I do not have much expertise in the formation of ancient complex civilizations the like of the Indus Valley and Harrapan, and I must leave this to the experts.
As for Indo-Europeans, it is mostly accepted that they had their beginnings in the area we now call the Pontic steppe, the more northern and northeastern shores of the Black Sea and the nothern Caucus mountians. The proto-Indo-Europeans are associated with the Yamnaya culture of the aforementioned regions, and like the neighboring peoples of the Afonosovo culture, were also a mixed population of half Caucasian hunter-gatherer ancestry and half East European hunter-gatherer ancestry. It is believed that a neighboring culture, the Boltai, were probably the first to domesticate the horse. This domesticate was adopted early on the the Yamnaya, and it certainly did revolutionize early Indo-European societies, and was likely one trigger to the subsequent migration of the Yamnaya west into Europe and eastwards into Central Asia, the Iranian plateau, and onwards to the Indian subcontinent.
The Sintashta/Andronovo and Corded Ware cultures, both cultures derived from the Yamnaya culture, are two examples of one of the earliest westward migration of proto-Indo-Europeans (Corded Ware), and eastward migration (Sinstashta). The Sintashta is associated with the early or ancestral proto-Indo-Iranians and the Sintashta are believed to have actually been a migration of Corded Ware proto-Indo-Europeans from central Europe into the Ural steppe as evidenced by strong atDNA (autosomal) genetic relationship between Corded Ware and Sintashta, with the latter carrying central European genetic components not found elsewhere in Europe or in the Yamnaya.
The Sintashta proto-Indo-Iranians are most likely behind the invention of the war chariot, as the earliest war chariots are found in Sintashta environs and amongst clearly Sintashta cultural elements. As such, the Indo-European and proto-Indo-Iranian expansion throughout Central Asia and southwards into the Iranian plateau and subsequently into the Indian subcontinent was likely driven by this new technology and spurred the speed at which the proto-Indo-Iranians came to quickly settle and introduce Indo-European languages in these areas.
It is important to note that alot of the spread of Indo-European throughout Eurasia was mostly done so through elite acculturation and assimilation of a larger and pre-Indo-European population. It also seems to be male-driven, and that Indo-European males had a much larger impact on the gene pool of substrate populations than their purported numbers would suggest. This is evidenced by strong founder effects in areas like the northern Indian subcontinent, were Indo-European and all West Eurasian associated maternal lineages are relatively rare (~10%) whereas Indo-European associated male lineages, specifically R1, in addition to I lineages, peak at very high frequencies in northern Indian/Pakistani males. The same happened throughout most of the European continent, as Indo-European male lineages and patrilineal descendants outnumbered males carrying pre-Indo-European lineages, as you can also see in frequencies of R1 and I in Spain, France, and the British Isles, and Scandinavia, and eastern Europe. In this respect, the Indo-European expansions are very similar to the earlier Afroasiatic expansions.