Phys.org posted a story about an article by researchers at the Max Planck Institute stating that "languages with a wide range of tone pitches are more prevalent in regions with high humidity levels. In contrast, languages with simpler tone pitches are mainly found in drier regions. This is explained by the fact that the vocal folds require a humid environment to produce the right tone."
But as far as we know, there is no human culture without singing. So... ?
Read more at: http://phys.org/news/2015-01-tonal-languages-require-humidity.html#jCp