European historians of the 19th century, followed Max Muller's idea, which was: The people of Saraswati-Sindhu civilization (Dravidian), retreated to south India, as tribal Aryans invaded them.
There is no evidence of a break in Indian tradition, going back 10,000 years. No break in ceramic styles, artistic expression, skeletal remains, and so on. If it is compared to that with regions that have suffered invasion, such as the Americas, one will see a clear break in all these things.
Aryan-Dravidian divide simply doesn't exist. This concept was a by-product of the racist discourse of the 19th century. Infact, Tamilian kings in South India and Sri Lanka (including Ravana of Ramayan) called themselves Aryan. The word Arya in Sanskrit simply means cultured. It is not a race.
Linguists also acknowledge that many language families existed in the past. What survives, represents complex interactions between different languages. It is recognized that Sanskrit, Greek and Latin belong to a family; while, Sanskrit and Tamil and Telugu belong to another. Culturally, India shows great unity as far back as we can go.