A Genetic Basis for Language Tones?

For the most part, the thousands of languages in the world today fall into one of two categories (notable exceptions being Japanese, some Scandinavian dialects and northern Spain's Basque tongue): tonal or nontonal. Two linguists believe they know the genetic underpinnings for these differences. During a study of linguistic and genetic data from 49 distinct populations, the authors discovered a striking correlation between two genes involved in brain development and language tonality.