John Allen Chau’s very presence on the island posed a danger to the Sentinelese, since they may not have developed immunity to the common microbes he carried with him. He also threatened their way of life: In recent years, given the growing consensus that modern visitors tend to erode the cultures of isolated tribes, the Indian navy has enforced a “no contact” policy with the Sentinelese and other tribes in the area, patrolling the waters to prevent infiltration by anthropologists and adventure-seekers alike.