Whistling languages - more forensic semiotics?

 This method of communication, in which the Spanish language is replaced by two whistled vowels and four consonants, has a peculiarity perfectly suited to this landscape of deep valleys and steep ravines. It has the ability to travel up to two miles, much further and with less effort than shouting.

http://www.bbc.co.uk/news/magazine-20953138

... There are no certainties about its origins. It is known that when the first European settlers arrived at La Gomera in the 15th Century, the inhabitants of the island - of North African origin - communicated with whistles.

These whistles reproduced the indigenous language. With the arrival of the Spanish, the locals adapted the whistling language to Spanish.

So the most likely theory is that the whistle came with the settlers from Africa, where there are records of other whistled languages.

Some locals recall its widespread use in the 1940s and 50s.

"In the old days, when the mountain caught fire, something that happens quite frequently in the island, the Guardia Civil came to pick us up," says Lino Rodriguez.