Whats the actual Indian history?

Hi Folks,I am under a big dilemma, as per my knowledge we have two theories of the origin of post Indus Valley Civilization India.First one says that the Aryans invaded the Indus Valley and later settled in northern and north-western part of India.So it is Aryans who are our fore-fathers.Second one says that it was inhabitants of Indus Valley only who shifted to the Ganges plain and southwards because of dire situation there. So according to it, the people from Indus valley are our fore-fathers.Well conclusively nothing can be said that which one is correct, but more weightage is given to the Aryan invasion theory.Should not the govt. be instituting a proper research of our history, I mean we dont know about our history but about Western history.
Pls comment.