By focusing on pitch or tone that gives meaning to words, which could be found in different languages, the researchers from the University of Miami were able to find the answer they were seeking. The research was quite extensive, as they had to examine over 3,700 languages. Out of these, they concentrated on 629 that had tones that were complex. Most of these had three or more tones that gave contrast to many vocal sounds.
What the researchers found was that complex-toned languages developed in areas that were either tropical or humid, including Southeast Asia and across Africa. Some other areas included were New Guinea, Amazonia and North America. On the other hand, languages that have simple tones developed in areas where the climate is dry or glacial.
Because frigid air is dry regardless of relative humidity, a difference in temperature by 40 degrees means that the water vapor capacity will have a 13-fold variance. Inhalation of cold air increases nasal fluid and increases bronchoconstriction, which leads to people breathing through the mouth. Oral breathing promotes the dehydration of the vocal tract and the evaporation of the liquid in the vocal cords cause the difficulty in vocalization. Think of how difficult it is speak when you have a chest cold and have dry mouth and laryngitis due to the cold weather. Now think back to the conditions eons ago when people contended with harsh environments, living in caves and tents, spending most of their time outdoors in very cold weather.
Adapting to the environment
Linguist Caleb Everett said that the results of their study somehow changed their understanding of how languages exactly evolved. He added that this did not mean that climate was the main determinant in the development of languages, but that it was one of the major factors that helped their formation. There were also indications, according to Everett that showed that the harsh environments where humans lived caused their language to evolve and adapt.
He said that when people inhale dry air, laryngeal dehydration results. This condition reduces the elasticity of the vocal fold. Thus it was probable that the complex tones became difficult to develop in areas where the climate was arid, especially in areas that were very cold. This is in contrast to areas where the climate was humid and warm.
The research results showed that tonal languages are notably rare in Central Europe where the climate is arid. It is because the human voice box is kept elastic and moist by humidity, which in turn enables the production of more complex and correct tones.