Those Aryan migrations into India have not been definitively proved (i.e., it is possible that the homeland of the Indo-European languages was or included India.) Further, even if the migrations occurred, they may have happened much longer ago than conventional Indo-Europeanists have supposed. And the Vedic literature may be quite a bit earlier than the conventional date of 1500 BC that is given to it.
See the new book by Edwin Bryant, The Quest For the Origins of Vedic Culture: The Indo-Aryan Migration Debate (Oxford U.P. 2001).
Thanks for the title, I'll check it out. I believe, however, it has been established that the Indus civilization of the Mojendo-daro (sp) era was not Vedic.