Arunachal Pradesh is the home of an endangered language known as Koro. It’s part of the Tibeto-Burman language family, a group of some 400 languages.
But until now, Koro was unknown to world linguists.
Only about 800 people are believed to speak it, with few under age 20.
Harrison, Anderson and Indian linguist Ganesh Murmu sat in the homes of the speakers, making recordings as people shared vocabularies and stories in Koro.
The researchers were in the region to study two poorly known languages, but in speaking to the locals, detected the third surprise language.
The scientists believe Koro may have sprung from slaves in the region, but they say more research is needed to determine precise origins.