In February a person by the name of Boa Sr died in the Andamans and with her death, the language named Bo was gone; she was the last known speaker of that ancient language. While Bo was a known language, Koro was not. It was only in 2008 that researchers found that such a language — spoken by 800 to 1200 people— even existed in Arunachal Pradesh.
The speakers of Koro had remained invisible to outside observers because their bright red garments, the rice beer they made and other details of their lives seemed no different from that of the speakers of Aka, the socially dominant language in the region, Harrison said.
“There’s a sort of a cultural invisibility; they’re culturally identical in what they wear, what they eat, the houses they live in…. They just happen to have a different word for everything,” Harrison said.
Koro also blends in because its speakers frequently marry Aka speakers (who number 4,000 to 6,000) and people who use another tongue, Miji (who number 6,000 to 8,000). And because the villages had been largely cut off from the outside world for so long, the languages in the region remain poorly studied.[Linguists uncover 'hidden' language in north India]
If you want to hear this language, National Geographic has the video.