Human children have a unique, and highly mysterious, ability to acquire proficient speech and language skills without the need to be formally taught. After only a few years, a typical infant has assembled a huge vocabulary of words, can use grammatical rules to combine them into a potentially limitless number of meaningful utterances, communicates these with rapid and precise coordination of the speech muscles, and is similarly adept at decoding the utterances of others. It has long been suspected that the answers to this puzzle may lie somewhere in our genetic makeup. Importantly, the human genome does not contain the information (the sets of words and rules) for any specific languages themselves; we all need exposure to a language in order to learn it. A child growing up surrounded by Dutch speakers becomes fluent in Dutch, while the same child growing up in Japan would learn to speak Japanese. Rather, our genes help to build brain circuits that are well-tuned to soak up language from the social environment.

For many years, it was only possible to speculate about potential genetic contributions to language acquisition. With the rise of new molecular techniques, scientists have now started to identify and study individual genes that are important. So far, most research has focused on searching for causative genes in children and adults who have problems with speech and/or language development that cannot be explained by another cause (like deafness or intellectual disability). It is clear that there is not just one single factor at play, instead an orchestra of genes and their interactions are responsible. Some genes have greater effects than others. For example, one gene with a large effect is FOXP2, the first gene implicated in an inherited speech and language disorder. If a child carries a disruptive mutation in this gene, it is enough to cause serious problems with learning to make sequences of speech sounds, problems that persist throughout life. In contrast to the rare severe mutations of FOXP2, more commonly occurring variants seen in other genes, such as CNTNAP2, ATP2C2, or CMIP have more subtle effects, increasing risk of language difficulties in small but significant ways.

While quite a lot is known about genetic variants that lead to language problems, there is less insight into genetic effects that make certain people in the general population better at acquiring language(s). Some of the genes involved in language impairments, like CNTNAP2, are also known to have effects on language development and function in people without disorders, yet further studies are required to uncover the genes and variants that might give some people a linguistic advantage. An exciting new step for this research will be to exploit the latest genomic techniques to look at the other extreme of the spectrum, people who have unusual talents in acquiring or using language.

Written by Katerina Kucera & Simon Fisher

Further reading:

The Language Fossils Buried in Every Cell of Your Body (link)

Graham S.A., Fisher, S.E. (2013). Decoding the genetics of speech and language. Current Opinion in Neurobiology, 23, 43-51. (link)