Most languages spoken in human populations can be divided into one of two categories: tonal or non-tonal. In tonal languages, the pitch of a word alters its meaning. Tonal languages include some Latin American and South-East Asian languages – for example, Chinese. Non-tonal languages are those in which the pitch of a word conveys emotion, but does not affect the meaning, as in English. Research published in the Proceedings of the National Academy of Science, USA, suggests that this difference has a genetic component. The tonality of the language of a population is linked to two genes, ASPM and microcephalin, that are associated with brain structure.
Populations that speak non-tonal languages tend to have relatively recent (37 thousand years ago) mutations in these genes, while populations that speak tonal languages have the older version. The exact functions of APSM and microcephalin are not yet known, but they are likely to be involved in embryonic brain development, as some mutations of these genes cause brain conditions like microcephaly (a condition where the person has a much smaller brain than the average for their age).
The authors of the study suggest that the new mutations control slight differences in the cerebral cortex, a part of the brain that plays a part in understanding language. However, it is possible that the correlation is only a coincidence, or caused by prehistoric migrations, and the two alleles are not the cause of the language differences.
The article this blog is based on is available from Science magazine, here: http://www.scientificamerican.com/article.cfm?id=genetic-basis-tonal-language
The original study is available from PNAS, here: http://www.pnas.org/content/104/26/10944.short
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