Words in code notes that “speakers of tonal and non-tonal languages have genetic differences”:
First, Dr Dediu and Dr Ladd checked that their two genes of interest really are unusual. They combined a database of 983 alleles that are known to vary across human groups with another enumerating how 26 discrete linguistic features (such as whether consonants aggregate at the beginnings and ends of words) are either used or not used in conversation by 49 populations. Picking apart a thicket of possible correlations, Dr Dediu and Dr Ladd found no general links between human genetic and linguistic characters.But one feature — whether a language uses pitch as well as vowels and consonants to convey word meanings — stood apart. Those, such as Chinese, that encipher meaning in pitch are called “tonal languages”. Those that do not, like English, are “non-tonal”. And it was versions of Dr Dediu’s and Dr Ladd’s two microcephaly-related genes that matched the 49 populations along tonal and non-tonal lines.
Dr Dediu and Dr Ladd believe the evolution of tonal and non-tonal languages interacted with the evolution of these genes.