Just as humans are different genetically, so are they diverse linguistically, speaking at least 6,800 known tongues worldwide. New findings suggest genetics could explain some of the variety seen in language by, at times, leading to preferences for tones. The means by which this link works remains unclear, and some researchers dispute whether it exists.

For the most part, languages are either unambiguously tonal or not. In tone languages, such as Mandarin in China or Yoruba in West Africa, the pitch of a spoken word affects its meaning. For instance, in Mandarin, ma said in a high, level tone means “mother” but in a low, rising tone means “horse.” In English, a word’s pitch conveys emotion but often does not influence meaning. (Notable exceptions to this dichotomy include Japanese, where words can differ depending on the pitch of syllables—technically, moras—within them.)