In a comment on a previous post, I wrote:
I would say that the modern population genetic data and the archaeological data are consistent with a Yamnaya incursion into Europe. The ancient DNA data is also consistent. There is no literary record, and neither genes nor archaeology inform us about language, but presumably the Yamnaya incursion is a candidate to which to tie IE expansion into Europe. The problem is that the earlier farmers are also a candidate for I.E. introduction into Europe. Neither genes nor archaeology can help us decide between the two. Most historical linguists like the shorter time depth and favor the Yamnaya theory. But their tools, e.g., "glottochronology" are riddled with flaws.
The archaeological record for India does not show a Yamnaya incursion or Andronovo incursion or any other significant incursion in the 1900 BC - 1200 BC timeframe. Language-wise - the Rg Veda is the oldest attested I.E. example but is known via oral tradition; and the Mitanni records with a few Vedic deities and I.E. words as its closest competitor; but the Indian archaeological record does not provide any evidence of language. (Re: Hittite, see below) India does not yet have any ancient DNA. Genetics of the modern population so far rules out any significant incursion into India 4000-2500 years ago - but India remains a grossly undersampled population.
The Saraswati River mentioned in the Rg Veda is named with other rivers; in the hymn, these other rivers are in the correct geographic sequence of rivers of the Indus and Gangetic systems. If we thus place the Saraswati, it was a mighty river then, it now corresponds to the seasonal Ghagghar-Hakra; the channel along of which the majority of Harappan civilization sites are found; it corresponds to the Saraswati, already dried up by the time of the Mahabharata. If we accept this identification it places the Rg Veda to before 2000 BC. Since Hittite is attested to 1600-1300 BC in written records (only), the Rg Veda would be the oldest attested I.E.
We need not accept this identification of the Saraswati, linguists such as Harvard's Sanskritist M. Witzel have theorized that some other river in Afghanistan was the original Saraswati, and for some reason the Rg Vedic people transferred the name to the already-dried up river bed that they found when they entered India.
The Rg Veda was composed in India, of that there can be little doubt. But the Saraswati timeline throws the historical linguists' 1900 BC - 1200 BC time line into confusion, so they hypothesize that the hymns are sometimes a memory of some other place where the "original" Saraswati was. They also dismiss the Rg Vedic mention of the sea and of hundred-oared boats, which are not there in the deep inland Afghan location that they want to place the "original" Saraswati, by saying that the composers were incorrigible boasters and exaggerators. Then, by their estimates, these memories were transformed into Rg Vedic hymns around 1400 BC. Then Hittite becomes the oldest attested IE language.