Mark Sicoli

Still from the series "In the Americas with David Yetman."Mark Sicoli

In some remote parts of Oaxaca, Mexico, local men can carry on whole conversations across long distances of the Sierra Madre del Sur mountain range. Rather than shouting across the rugged terrain, they make themselves heard though a complex series of whistles.

Researchers suspect the whistled talk could be as old as the earliest languages. But while some young people in the Oaxacan Cuicatlán District can still speak the language, the days of the unique form of communication is likely numbered.

Modern innovations, such as cell phones and walkie-talkies, are now more commonly used for long-distance communication. And the whistled language's roots -- the Chinantec spoken language -- is also itself threatened by the more prevalent usage of Spanish. A recent research project, "Documenting Whistled Speech Among Chinantecans," aimed to study the language before it's too late.

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"Whistled speech made the local Chinantec language portable across canyons, fields and along the steep slopes where the village houses cling to the hillsides, making travel physically challenging," project leader Mark Sicoli told Discovery News.

"Such rugged, inaccessible landscapes are the types of terrain where whistled versions of spoken languages have been developed in places as far from Mexico as the Canary Islands, Africa, Greece and Turkey, New Guinea, and St. Lawrence Island in the Bering Sea," added Sicoli, who is an assistant professor in Georgetown University’s Department of Linguistics.

Sicoli and his team traveled to the region in order to document and archive examples of whistled conversations transcribed in written Chinantec and translated to Spanish and English.

Sicoli also developed a map navigational task, which asked one speaker to whistle directions to a second speaker to follow on a map. The successful use of the whistling demonstrated just how effective this unique form of speech can be.

Most Chinantec words turned out to have a whistled counterpart. The archive, for example, includes whistles that translate to sentences like: "Do you have any edible fungus growing in your corn field?" "Where are you going?" "What are you going to do at noon today?" and "I'm going to eat tacos for dinner tonight."

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"Due to its acoustic range, whistling can substitute for standard vocalized speech over both short and long distances, alleviating pressure on vocal chords and overcoming the difficulties of communicating long distances over difficult terrain," Sicoli explained.

A short-distance whistled "conversation" is more like regular mouth-puckered whistling, while long-distance communications may involve the sports stadium-type finger in the mouth whistling. The researchers found that the language is spoken mainly by men, although women often understand the whistled language, even if they don't speak it.

Daniel Everett, a professor of global studies and sociology at Bentley University, pointed out that "many of the world's languages may be whistled. English's limitation to consonants and vowels is a restriction to one channel of discourse, while whistled languages illustrate that human languages need not be so constrained."

Everett added, "When we study languages like these, we learn that the perimeters of human capability are more encompassing and contain more richness than we would have otherwise known."

It is unclear when whistled speech first emerged.

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"Hypothetically, whistled speech could be as old as the earliest languages," said Sicoli, adding that it could even have been a component of proto-language -- the precursor of human language used by earlier hominid species.

"Whistling itself is something that has been self-learned by at least one ape," he added. "Bonnie, a female orangutan at the National Zoo in DC, taught herself to whistle for what seems to simply be the pleasure of it. What Bonnie shows is that, anatomically, whistling would have been in the range of potential sound-making behavior of archaic Homo sapiens, including Neanderthal and earlier hominids like Homo erectus and Australopithecines."

While whistled speech is likely very old, it may be fading fast as technologies like phones and radios make it possible to communicate across long distances and as Mexico's main language, Spanish, infiltrates more of the country.

"When a language is lost, we lose knowledge of ways and content of human speech and minds that can never be recovered," he continued. "Thus parts of the puzzle of human identity and the joy of human experience remain forever hidden from us."

For a description and audio of the language, click here.