Some interesting articles on the Andaman Islands:
Of note, the Andaman Islands have a very recent history of occupation. There is no reason to think they have been totally isolated for long. In fact, recent history is likely why they are so hostile to outsiders. With a census size of just about 100 people, they are on the edge of long term viability. It is hard to imagine they have been this isolated for 5 to 10 thousand years.