> I really doubt that "the oldest" language has any meaning at all, given that most (all?) living natural languages gradually evolved from an ancestor language.

There are some newer languages, which evolved quite suddenly rather than gradually.

https://en.wikipedia.org/wiki/Haitian_Creole

https://en.wikipedia.org/wiki/Tok_Pisin

https://en.wikipedia.org/wiki/Gullah_language

There is no reason to believe that any regional language of India could have arisen in this way, though.