A "hidden" language has been documented in an isolated hill tribe in a northeastern Indian region considered a "black hole" in the study of languages, linguists announced today.

The new language, Koro, is spoken by about a thousand people in Arunachal Pradesh (map), a state for which little linguistic data exist, due to restrictive entry policies, according to the linguists behind the findings.

Koro belongs to the Tibeto-Burman language family, which includes 400 languages such as Tibetan and Burmese. About 150 Tibeto-Burman languages are found in India, but a team with the National Geographic Society's Enduring Voices Project discovered that Koro was distinct from all other languages in its family. (The Society owns National Geographic News.)

The linguists happened upon the language in 2008 while researching another two poorly known languages—Aka and Miji—which are spoken in one small district.

While listening to these tongues, the researchers detected a third language, Koro.

"This is a language that had been undocumented, completely unrecognized, and unrecorded," said researcher Gregory Anderson, director of the Living Tongues Institute for Endangered Languages.

What's more, the newly identified Koro tongue may be endangered: Only about 800 people are speakers—most of them older than 20—and the language hasn't been written down, Anderson noted.

Newfound Language in a Class By Itself

The team climbed steep hillsides and took to bamboo rafts to access the remote villages, where people make a living raising pigs and cultivating rice and barley.

Going door-to-door among the stilted bamboo houses, the team recorded villagers speaking the newfound language.

It's unknown how the Koro, who number between 800 and 1,200 people, came to live as a subtribe of the 10,000-person Aka tribe.

But it's clear that Koro differs greatly from Aka, the team found.

For instance, Koro's inventory of sounds is completely different, as is the way sounds combine to form words. Words and sentences are built differently in Koro too.

For example, the Aka word for "mountain" is "phù" while the Koro word is "nggõ." Aka speakers call a pig a "vo," while to Koro speakers, a pig is a "lele." The groups share about 9 percent of their vocabulary.

"Koro could hardly sound more different from Aka," linguist K. David Harrison of Swarthmore College writes in his new book The Last Speakers. The linguist is also a National Geographic Society fellow.

"They sound as different as, say, English and Japanese."

Language Differences Downplayed

Though they lack a common language, Koro speakers and Aka speakers insist there is no difference between them, Harrison noted.

The coexistence of separate languages between two integrated groups that don't acknowledge an ethnic difference is very unusual, the Living Tongues Institute's Anderson noted.

Typically, the minority language in such an arrangement would lose ground to the majority language and in time die out—or the smaller group would maintain its own language by asserting a unique identity.

But in the villages of the Aka and the Koro, in the shadow of India's contested border with China, everyone maintains the tribe and subtribe are the same but for a small variation in dialect.

"Local people downplay the difference in the languages," said Swarthmore's Harrison, who helped Anderson in his research, along with Ranchi University's Ganesh Murmu. "But they are radically different."

Koro Language Origin "Pressing Concern"

"Linguistically, their enigmatic origin is a pressing concern," said the Living Tongues Institute's Anderson, who will describe Koro's documentation in an upcoming edition of the journal Indian Linguistics.

"When did the Koro end up submerged within the Aka, and how did that come to be? Our most pressing task is getting decent documentation out into the professional domain so that specialists in other Tibeto-Burman languages can weigh in."

K.V. Subbarao, a professor at the Centre for Applied Linguistics and Translation at the University of Hyderabad in India, said Koro's uniqueness is an "interesting case."

"It is quite possible that two living communities can coexist and still maintain their separate languages," said Subbarao, who was not involved in the research.