Genetic differences between human populations may have influenced which languages are spoken around the world today, research has suggested.

People who carry particular variants of two genes involved in brain development tend to speak nontonal languages such as English, while those with a different genetic profile are more likely to speak tonal languages such as Chinese.

In tonal languages, which are most common in South East Asia and sub-Saharan Africa, subtle differences in pitch can change the meaning of vowels, consonants and syllables. Nontonal languages, which prevail in Europe, the Middle East and North Africa, use pitch only as a way of conveying emphasis or emotion.

The new findings from the University of Edinburgh also suggest that the very first human languages were probably tonal, sounding more like modern Chinese or Zulu than English or French. The genetic profile that appears to predispose to nontonal languages evolved only about 5,800 years ago, implying that all languages were probably tonal before that.

All humans have the innate ability to speak either type fluently, but the research indicates that genes may make one class slightly easier to learn. This raises the possibility that over thousands of years these differences could have guided the evolution of local languages according to the genetic variants in particular ethnic groups.

As most people in ancient China carried genes that favoured tonal language, Chinese would have become more tonal. In Europe, the genetic position was reversed, and local languages developed along nontonal lines.

“This does not mean that people with one set of genes cannot speak the other type of language, or that you have to be any smarter to learn one of these groups of languages rather than another,” Robert Ladd, who led the research, said. “What we have found, though, suggests that these genes might have a very small effect on individuals, and a larger effect on the populations in which they live. As the language is passed on culturally, it would then be more likely to develop along one path than the other.”

He cautioned, however, that the research had so far found only an association that appears to be more than chance, and that more work was needed to confirm a causal effect.

The study is published in the journal Proceedings of the National Academy of Sciences.

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