First off, what are the obvious reasons you are talking about?  And what linguistic standards, scholars and consensus are you referring to? There is no such thing.   The Dravidian theory, is just that, a false theory that was suggested but not proved by Colonial rulers some 200 years ago.  It has largely been debunked and rejected by most modern historians including the famous Dr. Dani, a pioneer and the foremost expert in Indus Valley Civilization.  Get your facts straight and please only post veriable and accurate data in this article.  Cheers.  