According to Survival International there are around 100 uncontacted indigenous groups worldwide, a few dozen of them living in the Amazonian rainforest. One of them, the Carabayo, lives in voluntary isolation in the remote upper Puré River region in the Colombian Amazon rainforest. The most recent evidence of the Carabayo's persistence are aerial photographs of their roundhouses taken in 2010 which were published in the book Cariba Malo by the Colombian researcher Roberto Franco.
In early 1969, a military commission on a rescue mission, made violent contact with the Carabayo and took one family hostage. "While this family was held captive, speakers of all living languages of the region tried to communicate with them but failed," says Frank Seifart of the Max Planck Institute for Evolutionary Anthropology. "Researchers thus concluded that Carabayo was not related to any living language in the region."
Frank Seifart and Juan Alvaro Echeverri have now compared the Carabayo words with historical wordlists of extinct languages of the region that were documented by explorers in the 19th century. "Our comparison of the Carabayo data revealed that a number of Carabayo forms match corresponding Yurí elements, but none match forms of the other languages," says Seifart. The researchers identified four Carabayo forms -- a first person singular prefix, and the words for 'warm', 'boy' and 'father' -- to match corresponding Yurí forms well. "The strongest evidence for a link between Carabayo and Yurí comes from the first person singular prefix," says Seifart. "Personal pronouns are known to be especially resistant to borrowing which is why their similarity indicates a genealogical link, rather than language contact."
The researchers then compared Carabayo to languages spoken in the Colombian Amazon area nowadays and found a number of very good matches between Carabayo and Tikuna, but not with any other living language of the region. "What adds credibility to these matches is that they exhibit regular sound correspondences: For instance Carabayo g corresponds to Tikuna ng in a number of words. That can hardly be a coincidence," says Seifart. The researchers conclude that Yurí, Carabayo and Tikuna are genealogically related, with Carabayo somewhere in the middle between Yurí and Tikuna, but probably closer to Yurí. "The ease with which Carabayo data could be interpreted by a native Tikuna speaker additionally suggests that these languages are relatively closely related and may even form -- or have formed in the past -- a dialect continuum," says Seifart.
Science Daily. 2014. “Family ties in the language jungle: Amazon language relationships revealed”. Science Daily. Posted: April 16, 2014. Available online: http://www.sciencedaily.com/releases/2014/04/140416172249.htm