Whistle while you work

Sometimes you get a song stuck in your head.  You keep thinking about it all day, and maybe you even start to whistle the tune.  But whistling isn't always used just for music.  Have you ever been out in public, and a parent (perhaps yours) whistles for their child’s attention?  Or maybe you were talking a walk in the park, and a dog owner is whistling for his dog to come.  The individual who is whistling in these cases is usually not using the sing-song type of the whistle, but instead, almost a talking, or shouting kind of whistle, that really caries no tune.  But it’s really very different from talking, right?  After all, you can’t speak by whistling… But, in fact, you can.
On one of the Canary Islands known as La Gomera, off the northwest coast of Africa, the inhabitants have been using a whistling language since before the Spanish colonized the island in the 15th century.  Due to the landscape of rocky hills and valleys, the people of La Gomera developed a unique, but simple method of transcribing their spoken language (and later Spanish) into series of whistles that could be heard from up to two miles away.  When Spanish became the primary language on the island, the whistle (or, El Silbo, which comes from the Spanish verb 'silbar', 'to whistle',) changed to accommodate the different sounds and structure of the Spanish language.
The language is made up of two whistled vowels, and four consonants.  A demonstration can been seen below:

It was particularly useful to shepherds, as they communicated over vast distances, but also to the rest of the people, as they often lived far apart from one another.
After the invention of telephones, the language began to decline, and was in danger of extinction, as many regarded it as “something from peasants” (Plitt, 2013).  However more recently, there has been a resurgence as the government of La Gomera now views it as an important part of their culture, and has even made it a compulsory school subject on the island.  Today it is a major tourist attraction for the relatively small island.  It has also revealed insights into the human brain for the field of linguistics.   A study using an FMRI showed that when those who “Spoke” El Silbo listened to recordings of it, the parts of the brain associated with language and comprehension were activated, whereas those who were not accustomed to El Silbo did not even recognize it as a language. (Schwarz, 2005)

This, as well as evidence of other languages such as American Sign Language, prove that humans are indeed capable of interpreting stimuli other than spoken word into language (Although some argue that El Silbo is not quite a full language).
Although El Silbo Gomero is not the only recorded whistling language/communication method, (others have been documented in Greece, Turkey, China, and Mexico) it is the most well studied, and widely spoken of them.
El Silbo Gomero is a great example of how the different methods by which we connect are infinitely vast and diverse and how humans will not allow distance to stop them from communicating with one another.

References: 
http://www.lagomera.travel/en/about/history-of-the-island-of-la-gomera.aspx

Plitt, L. (2013, January 10). Silbo gomero: A whistling language revived. BBC News Magazine, Retrieved from http://www.bbc.co.uk/news/magazine-20953138

Schwarz, J. (2005, January 5). Shepherds whistle while they work and brains process sounds as language.UW Today, Retrieved from 
http://www.washington.edu/news/2005/01/05/shepherds-whistle-while-they-work-and-brains-process-sounds-as-language/