Indo-Aryan migration

Substrate influence

Most of the languages of North India belong to a single language family, the Indo-Aryan subgroup of the Indo-European family of languages. The languages of South India belong to a different language family, the Dravidian languages, which has not been proven to be linked with any other language family.

The presence of retroflex consonants (including L) in Vedic Sanskrit is generally taken by linguists to indicate the influence of a non-Indo-European speaking substratum population.

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  These sounds are found throughout Dravidian and Munda and are reconstructed for proto-Dravidian and proto-Munda.
  
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  They are neither reconstructible for proto-Indo-European nor for proto-Indo-Iranian.
  
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  They are also extremely rare among other Indo-European languages (they phonetically emerged in Swedish and Norwegian only in recent centuries).
  
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  Presence of words with Dravidian and Munda etymologies in Sanskrit (some of these etymologies have been challenged, though most have not).
  

Critics argue that the "substratum" influences from Dravidian and Munda could equally well be adstratum influences through mutual contact without conquest, or superstratum given the advanced nature of the precedent Mature Harappan culture.

While Dravidian languages are primarily confined to the South of India, there is a striking exception: the Brahui (which is spoken in parts of Baluchistan), the linguistic equivalent of a relict population, perhaps indicating that Dravidian languages were formerly much more widespread and were supplanted by the incoming Indo-Aryan languages. David McAlpin has demonstrated that the Dravidian languages are related to Elamite, a language once spoken in southern Iran.