The Sentinelese are believed to have been isolated since the last major initial human migrations out of Africa 60 to 70 thousand years ago. Their isolation has likely preserved unique genetic traits. The Sentinelese are related to other indigenous peoples of the Andaman Islands, such as the Onge, Jarwa, and Great Andamanese. Studies on these groups indicate that they have some of the earliest genetic markers found in Asia. The genetic diversity among the Andamanese tribes, including the Sentinelese, is thought to be low due to their small population sizes and long-term isolation. Due to their isolation, the Sentinelese may lack immunity to common diseases found elsewhere–a significant concern.