The Sentinelese, also known as the Sentineli and the North Sentinel Islanders, are a pre-Neolithic indigenous people who inhabit North Sentinel Island, located in the Bay of Bengal in India.
An uncontacted people, the group, estimated to be composed of anywhere from 40 to 500 individuals, is believed to have lived on North Sentinel Island for as long as 55,000 years and speaks the Sentinelese language, a language isolate not related to the native languages found on the surrounding islands. Indian authorities have put in place laws that prohibit any individual being closer than 4,8 km to the island, for both the safety of outsiders, as the Sentinelese are known to be hostile, and the Sentinelese themselves. Being an isolated group, they likely do not possess the genetic immunity to survive exposure to common viruses, such as influenza and measles.
Unlike other ethnic groups found in the Andamanese Islands, who were more welcoming to outsiders and now interact with them somewhat regularly, the Sentinelese appear to have consistently refused any interaction with the outside world. [Via: wikipedia]