Around 800 people are believed to speak the Tibeto-Burman language.
An expedition team discovers a yet unrecorded language, called Koro.
The language was found in India's rugged and hilly Arunachal Pradesh region.
It's believed only around 800 people speak the language and it's highly endangered.
A team of linguists announced Tuesday that they have discovered a new and unique language, called Koro, in northeastern India, but immediately warned that it was highly endangered.
Only around 800 people are believed to speak the Tibeto-Burman language, and few of them are under the age of 20, according to the researchers who discovered Koro during an expedition as part of National Geographic's "Enduring Voices" project.
The language, they said, has never been written down.
"We found something that was making its exit, was on the way out," said National Geographic fellow Gregory Anderson, one of the leaders of the expedition that discovered Koro.
"If we had waited 10 years to make the trip, we might not have come across close to the number of speakers we found," he said.
Koro is so distinct from other Tibeto-Burman languages -- around 150 of which are spoken in India alone -- that the expedition team was unable to find any other language from the same family that was closely related to it.
It was discovered in the Arunachal Pradesh region of India, a rugged and hilly part of the subcontinent which visitors require a special permit to enter. Few linguists have worked in Arunachal Pradesh and no one has ever drawn up a reliable list of languages spoken there.
The National Geographic expedition, which also included Indian linguist Ganesh Murmu of Ranchi University, was, in fact, in search of two other languages, Aka and Miji, known to be spoken in a small district of Arunachal Pradesh.
Going door to door among the bamboo houses that sit on stilts in the hillside villages of the region, the team spoke to villagers and recorded their vocabularies.
And while they were doing so, they began to detect a third language, which was not listed in standard international registries or even in Indian language surveys. That third language was Koro.
The linguists made the first-ever recordings of Koro, capturing thousands of words during their expedition, which began in 2008.
The new language has a completely different inventory of sounds than other languages in the region, and its own way of putting together words and sentences.
For example, in Aka, the word for "pig" is "vo." In Koro, a pig is a "lele."
Despite their geographic proximity, the two languages "sound as different as, say, English and Japanese," National Geographic fellow David Harrison, one of the leaders of the expedition, said in the recently published book "The Last Speakers."
With Koro, linguists now count 6,909 languages worldwide.count
But around half those languages are endangered, the victims of cultural change, ethnic shame, government repression and other factors, according to linguists.
One of the aims of National Geographic's Enduring Voices project is to document vanishing languages. The team that discovered Koro plans to return to India in November to continue studying the new language.
A scientific paper on Koro will be published in the journal Indian Linguistics.