One thing that’s bothered me is that Europeans actually figured out quite quickly from the 16th century on their languages were similar to Hindi. But we have no record classical Greeks or Romans did to Sanskrit, though their languages were much more similar.
As I’ve mentioned before, they might have not figure this out on their own: contemporaneous H& Mohd lexicographers already organized words as lists of homologs (sometime analogs as they did not fully realize homology). More than one person has indicated that this might have inspired or provided the source material for some one like Jones.
Well before that there was dastur nairyosa~Ngha dhAvala who seems to have recognized the Indo-Iranian monophyly (not a big deal at all, still…) in the tradition of using Skt in Iranic commentary.
However, one could say that the “modernization” of the Aristotelian linguistic ideas by Wilhelm von Humboldt, the brother of Alexander among others provided “substrate” on which evolutionary hypothesis came to explain the homologies. A comparable intellectual setting was at that point not widely available in India. However, for a surprising early linguistic theory that I interpret as an understanding of divergence of ancient speech into various alternative versions see the mysterious sUkta 10.71 of RV. Some day might elaborate my thoughts.