The Origins of the Indo-European Gods

Kevin McLean says there is no one-to-one relationship between the primary Indo-European gods as in given a perfect knowledge of history could we authoritively create an interpretatory or Romano of the entire pantheon. Some mythological parallels seem more close to Jupiter they would just say that's Mercury and when they see Thor with a hammer they say that's Hercules you know. But actually comparative mythology doesn't work the same way that interpretate Romano does like the Romans had this very crude way of doing it whereas George the Maziel or Jan Povell and these kind of academics have a much more sophisticated method of comparing them.