Thanks to Pratik, I found this interesting piece in the Telegraph about the Indian Genome Variation Project, an ongoing study by a consortium of six Council of Scientific and Industrial Research (CSIR) laboratories and the Indian Statistical Institute, Calcutta. Here's one of the broad conclusions (quite unsurprising, if you ask me):
... [The Project]has provided the strongest genetic evidence yet to suggest that several populations have intermingled in India over the centuries.
Dravidian lineages have mixed with Indo-Europeans, Austroasiatics have mingled with Dravidians, and bridge populations in central India are blends of Dravidian, Indo-European and Himalayan groups.
Here's a very interesting manifestation of this general result:
... [S]ome Hindu caste groups are genetically closer to Muslims in the same geographical region than to their own caste cousins elsewhere in India.
But this bit is really sad:
“We had intense debates on whether to reveal the names of communities,” said Mitali Mukerjee, project coordinator at the Institute of Genomics and Integrative Biology (IGIB), New Delhi.
“I don’t think scientists are prepared yet to understand the full social ramifications if such information is made public,” Mukerjee told The Telegraph.
Pratik has some more links.