I might only be moderately qualified to answer this question, but for me (or anybody else) to do so would require a lot more information about what you're looking for in an answer. Could you narrow it down a bit?

As it is, you're asking a question about a culture group that sweeps literally all recorded history, from (possibly) the Indus Valley civilisation all the way to today's independent Indian state, along with huge questions of ethnic, linguistic, religious and national identity.