Hinduism is a very ancient religion and has predominated the area of modern India for millennia. It's a complex religion with a very large pantheon that doesn't seem to be strictly regulated by any "official" body. In fact, I have heard that there are so many gods that some are specific to just individual families and their dedication to them and no other believers seem to mind too much.
In light of this, what mythoi existed in the area before Hinduism predominated? Did they affect modern Hinduism in any way? If it is the case that we really don't know, please be sure to cite reputable sources that state there is no evidence of anything else existing there previously.