"Biologist Gyaneshwar Chaubey from an Estonian research centre and his collaborators in India say their genetic analysis suggests India has not witnessed any massive influx of populations for at least 12,500 years." (www.telegraphindia.com/1150628/jsp/nation/story_28288.jsp#.VjJPFJm6bqB)
/r/askanthropology or /r/anthropology could give better answers.Why not ask your question in those two subs at the appropriate times as well?