Climate influences human speech development

Climate and human speech development

Variations in human speech exist across regions and continents. Linguists and researchers have long debated whether geography has affected this phenomenon. Nonetheless, a group of researchers uncovered a striking pattern: variations in human speech correlate with variations in climate or prevailing geographic temperature.

Researchers from the University of Miami, the Max Planck Institute for Evolutionary Anthropology, and the Max Planck Institute for Psycholinguistics examined more than 3,700 languages across different regions of the globe. They intended to draw the connection between climate and human speech development, particularly by discovering an association between the environment and consistency in vocal sounds across different languages in different geographic areas.

The researchers subsequently found out that out of the examined languages, 629 have complex tones and interestingly, these languages are spoken in tropical regions including Africa and Southeast Asia, as well as in humid regions of North America, Amazonia, and New Guinea.

Hence, the results ultimately imply that languages with complex tones or those that use three or more tones for sound contrast, are more likely to have developed and occurred in humid regions as opposed to languages with simple tone that are commonly found in desiccated regions, whether frigid areas or dry deserts.

Climate influences human speech development

This map shows the distribution of languages with complex tone (red dots) and without complex tone (blue dots) in the Phonotactics Database of the Australian National University. Darker shading on map corresponds to lower mean specific humidity. Photo credit: Caleb Everett/University of Miami

“In my estimation, it changes a bit our understanding of how languages evolve,” said Caleb Everett, lead researcher and professor in the Department of Anthropology at University of Miami. “It does not imply that languages are completely determined by climate, but that climate can, over the long haul, be one of the factors that help shape languages.

“More broadly, this suggests another non-conscious way in which humans have adapted to their very different and harsh environments,” Everett added. “Also, there may be some health benefits to certain sound patterns in certain climates, but more research is needed to establish that in a satisfactory way.”

Drawing from extensive experimental data cited in the research, the researchers explained that inhaling dry air commonly found in dry or cold areas causes laryngeal dehydration and decreases vocal fold elasticity. The resulting sounds produced by the vocal chords are jittery and shimmery. Over the long run, the environmental or to be specific, the climatic condition caused adoption of easy-to-produce sounds or simple vocal tone and pitch.

Further details of the findings are found in the study “Climate, vocal folds, and tonal languages: Connecting the physiological and geographic dots” published in Proceedings of the National Academic of Sciences. Co-researchers are Damian E. Blasi and Sean Roberts, from the Max Planck Institute for Evolutionary Anthropology and the Max Planck Institute for Psycholinguistics.