Birds use whistling as a form of communication, from warning sounds to mating rituals or establishing location. But can it be used by humans as a more evolved language?
Well, it turns out that some cultures have developed very advanced. Examples are known mostly in West and South Africa, Mexico, parts of South America, Nepal and New Guinea.
The most widely studied whistled language is silbo, which is used in La Gomera, one of the Canary Islands. According to the following reportage from time.com, although it is not as widely used as in the past, silbo is still taught in schools and understood by most locals. It is based on Spanish language and imitates its phonemes.
Due to the nature of whistling, vowels are much easier to reproduce than consonants, but silbo speakers can still have some pretty elaborate conversations. Check it out!