Well one of the "biggest taboo" ie -eating meat of cows happened in vedic times, as is substantiated by historic texts and references to feasts in ancient texts - (however one professor was beaten for publishing a book with proof on this by Bajrang Dal activists). The other taboo is not really taboo for all Hindu's. In a very small minority no doubt but there are sects / tribes that are Hindu and bury their dead. So these taboos do not "prove" either point of view.