Actually, the aryan invasions don't date that back. And there is sufficient genetic evidence (as in DNA testing google it), that back up the aryan invasion theory. For example, specific proteins dna proteins of brahmins/some other higher castes match with those of europeans. You'll also see lots of genetic diseases that are only prevalent in the european community to be in the brahmin community (though not south indian brahmins and probably not most nepali brahmins), like red-green color blindness. my dad has that. What's hilarious is that some indian people think they have blond hair and blue eyes. now that's impossible (excluding some non hindu kashmiris and immigrants of kalash). Moreover, being of a pure-bred indo-aryan stock is much more harmful in an environment like nepal than it is helpful. Ex, skin's not thick enough to withstand the sun etc. And since the whole 'pure' thing brought on massive inbreeding, there tends to be high cases of autism, downs syndrome, etc.