Talking Across the Valley

AOn the island of La Gomera, in the Canaries, a farmer can hold a conversation with a neighbour three kilometres away without a phone and without shouting. He whistles. Silbo Gomero, the island's whistled register of Spanish, converts ordinary sentences into piercing tones that carry across the deep ravines slicing the island — terrain where walking to your neighbour might take an hour, and where a whistle arrives in seconds. The practice is no party trick with a fixed list of signals: a skilled silbador can whistle any sentence the Spanish language permits, from gossip to funeral announcements, and be understood.

BWhistled languages are rare but not unique to one island. Linguists have documented dozens of them, and the map explains itself: they cluster in mountains and dense forest — the Atlas mountains of Morocco, villages in the Turkish highlands, communities in the Amazon — wherever the landscape defeats the spoken voice. Whistles succeed there for reasons of pure physics. A whistle concentrates all its energy into a narrow band of high frequencies, which travel much further than the scattered frequencies of speech and cut through the background noise of wind and water. Under good conditions a whistled sentence has been measured travelling as far as ten kilometres — a hundred times the useful range of a shout, at a fraction of the effort.

CWhat makes such systems linguistically remarkable is that they are not codes learned separately, like Morse, but the same language in a different clothing. A whistler takes the melody and rhythm of the spoken sentence — the rises and falls of its vowels, the breaks of its consonants — and reproduces that skeleton in pitch alone. The information that survives is incomplete, which means many words become ambiguous when whistled; listeners fill the gaps from context, much as readers of a text message decode its abbreviations. Brain-imaging studies underline the point. In experienced whistlers, whistled sentences activate the same language regions of the brain that spoken sentences do, and people who do not know Silbo process the sound as they would any melody: the brain treats it as language only when it is language to the listener.

DThe twentieth century nearly ended the tradition. Roads reached the villages, telephones reached the houses, and mass tourism drew islanders into towns where whistling marked a person as rural and old-fashioned; by the 1970s and 1980s, parents on La Gomera were quietly declining to pass Silbo on. The rescue came from an unusual direction: the school timetable. From 1999, the island's government made Silbo a compulsory subject in its primary schools, and in 2009 the practice was inscribed by UNESCO on its list of humanity's intangible cultural heritage. Today thousands of children whistle competently, tourists attend demonstrations in mountain restaurants — and linguists note, with a certain irony, that the language owes its survival to precisely the institutions that once made it unnecessary.

ESilbo's story is a small window onto a large question: what a language is for, and what is lost when one channel of it disappears. The whistled registers never carried information that speech could not — but they carried it where speech could not go, and their decline tracks the arrival of technologies that solved the same problem with less beauty and less skill. On La Gomera the whistlers now include teenagers who message each other by phone in the evening and whistle across a ravine in the afternoon, apparently untroubled by the contradiction. A tool does not have to be necessary, their example suggests, to be worth keeping.