Two neighboring archipelagos in the eastern Indian Ocean, the low-slung Andaman and Nicobar Islands include 572 tropical islands, of which only 38 are permanently inhabited. Settled early in human history and then isolated over thousands of years, the islands developed unique aboriginal cultures that continued almost uninterrupted until the 1850s. Some, such as the people of Sentinel island, still live according to Stone-Age traditions and continue to refuse almost any contact with outsiders.