Can You Hold a Conversation by Whistling? Across a Valley, Yes

These are not codes with a fixed vocabulary of signals but the local spoken language rendered in a different medium. A whistler reproduces the changes in pitch and loudness that carry the information in speech, using a single tone that rises, falls and breaks in imitation of what the voice would do. Vowels are mapped onto pitch levels and consonants onto the transitions and interruptions between them, so a listener reconstructs the words from a far thinner signal than speech provides. The result is that a whistler can say anything the language can say, including new sentences the listener has never heard, which is what distinguishes these from drum signals or horn calls.

The distribution follows terrain rather than culture:

• •Steep valleys where neighbours are close in sight and far apart on foot
• •Dense forest where visibility is short and shouting does not carry
• •High mountain pastures where herders work alone at a distance
• •Places where crossing to speak in person costs an hour or more
• •Communities whose work is spread out rather than concentrated
• •Languages present in each case are unrelated, which shows the medium is the driver

The practical advantage is the whole reason for the practice. A whistle concentrates energy into a narrow band of frequencies that cuts through background noise and travels considerably further than a shout, with distances of several kilometres reported and verified in favourable conditions across valleys. Shouting scatters energy across a wide band and is absorbed and masked far sooner. The signal is directional and works across terrain that blocks nothing but sound. It leaves the hands free and requires no equipment. Against that, it is public, since anybody in earshot receives the message, which communities have exploited for announcements and which limits what is said.

Whistling is one solution among several to the same problem and the others clarify what makes it unusual. Talking drums in West Africa reproduce the tone patterns of a tonal language on an instrument whose pitch can be varied by squeezing, and they likewise convey open-ended messages rather than fixed signals. Horns and conches carry further and encode far less, generally a small set of agreed meanings. Smoke and beacon fires transmit one bit of information over enormous distances. Semaphore and flag systems encode letters and require line of sight and daylight. What distinguishes whistling and drumming from the rest is that both carry the structure of an actual language rather than a code agreed in advance.

Around seventy such systems have been documented and most are in decline. The best known is used on La Gomera in the Canary Islands, where a whistled form of Spanish nearly disappeared before being made a compulsory school subject in 1999 and recognised by Unesco in 2009, which has revived it substantially. A whistled form of Turkish survives in the Black Sea mountains and has been studied for what it reveals about how the brain handles language, with research finding that whistled speech engages both hemispheres rather than being processed as ordinary language is. Systems have been recorded in Mexico, Greece, the Amazon, West Africa and elsewhere. Mobile telephones have removed the practical need almost everywhere.

These systems render an ordinary spoken language as pitch and interruption in a single tone, so anything sayable can be whistled, unlike a code of fixed signals. They occur wherever terrain puts neighbours in sight and far apart on foot, in unrelated languages, which shows the terrain drives it. A whistle concentrates energy into a narrow band and carries several kilometres. Around seventy have been documented and mobile telephones have ended the need.