The Caucasus Mountains stretch between the Black Sea and the Caspian Sea. The Caucasus area overlaps six countries - Armenia, Azerbaijan, Georgia, Iran, Russia and Turkey. The term Caucasian was introduced in Racial Science in 1785 as philosophers tried to wiggle their way out of the problematic conclusions of the Enlightenment given the obvious conclusions with regards to Human Rights. How do you tear down and justify superiority at the same time? There was never any consensus about where the delineation stood. For the obvious reason that in nature borders aren't lines. Things are fuzzy. The similarities between Sanskrit, Greek and Latin are another indication of the fuzziness through Indo-European languages. The Abrahamic Religions another. If you look to history to justify borders, you will only discover the fuzziness.
Attempts at classification always fail