The religious traditions that many Indians now regard as their “ancestral” religion was developed by the Aryan-speaking people in northern India. These Aryans used Sanskrit as their holy language.
At the same time, the Dravidian-speaking people of southern India maintained their own religious traditions.
The Dravidians also interacted with the Aryan-speakers and so north and south gradually adopted similar religious traditions. For instance, the main Hindu gods (Shiva, Vishnu, The Goddess or Durga) are now worshiped in both northern and southern India.