That doesn't explain Sri Lanka which is past South India...
Edit: The actual answer is North/Eastern Indians speaking an IE variant immigrated to Sri Lanka in the 5th/6th centuries and became the dominant language there since (Sinhala)
Sri Lanka only became an island like 500 years ago. It was a storm in 1480 that disconnected the passable land bridge that once connected it to mainland India.
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That doesn't explain Sri Lanka which is past South India...
Edit: The actual answer is North/Eastern Indians speaking an IE variant immigrated to Sri Lanka in the 5th/6th centuries and became the dominant language there since (Sinhala)
Could it be that Sri lanka is an island
Sri Lanka only became an island like 500 years ago. It was a storm in 1480 that disconnected the passable land bridge that once connected it to mainland India.
Sri Lanka's been inhabited for over 100k years.