Earlier quoted context omitted.
> the society of Rig-Veda I fail to understand how the Rigvedic society can be connected to this DNA research. Rigveda never mentions anything beyond the Punjab/Swat/Haryana region in any of the hymns. The flora and fauna mentioned in it is also exclusive to this region. Lastly there is no mention of an ancient homeland both in Rigveda and Avesta.
I think this comment is based on some confusion about how languages spread. Languages spread along with people, but while a local language may be replaced, the people are not generally replaced with the language. There may have been some genetic mixture, there may have been a time where they were conquered by them for a time, but there's no sense in which the people who wrote those works _were_ Yamnayan, any more tha…
The problem of IE is of course very abstract, while the problem of, e.g., Celts is much more concretely paradoxical (continental and island Celts share the language family but not a lot of archaeology and a dubious amount of genes). However, it is still a more or less commonly accepted fact that at some point in the past PIE peoples spread like wildfire, bringing their dialects, genes, and culture to a very large area, and it is of huge historical interest to know where they started from.
The fact the IE epic and mythological traditions have zero memories of all this, I would say, is interesting but does not prove or disprove anything.