It's important because the linguistic analysis that identified migrations and population groups disproves certain 19th century racial theories.
And what's that got to do with anything?
I haven 't studied the history of India, but my understanding is that the British colonials found a less hierarchic society and turned it into a more hierarchic society
Perhaps you should study more. The caste system existed before the Romans, let alone anything recognisable as Britain.
But what's that got to do with anything?