Linguistics
One human language remains completely unknown — not a single word has ever been recorded
The Sentinelese people of North Sentinel Island in the Andaman Sea have rejected nearly all outside contact for centuries, and Indian law now bans anyone from approaching the island. As a result, linguists have no word list, no grammar and no audio recording of their language, not even confirmation of which language family it might belong to. It may be the last language on Earth about which literally nothing is documented.