Cognition

A Gene for Language?

Speech is influenced by many genes that have nothing to do with language.

Posted Dec 10, 2014

Timmy and Tommy are having a counting contest. “One,” says Timmy. “Two,” says Tommy. “Three,” Timmy replies. “Four,” Tommy responds. Timmy pauses. He can’t think of a higher number, and neither can Tommy.

Of course, counting contests are pointless. As any fourth grader can tell you, no matter how high you count, there’s always a higher number. Mathematicians put it this way: for any n, there’s n+1. This property of numbers is known as recursion.

Put simply, recursion is the process of extending a pattern by placing it inside itself. Recursive patterns occur widely in nature, from the structure of DNA to the number of petals on a daisy. Recursion is a feature of many of our day-to-day behaviors, as when we wash, rinse, and repeat.

Likewise, recursion is also an important characteristic of human languages. Just as there’s no highest number, there’s no longest sentence either. Children pick up on the recursive nature of language even before they enter grade school, and they play language games that extend sentences indefinitely. I saw the dog … that chased the cat … that caught the rat … And so on.

This game involves placing one sentence inside another sentence, just like a set of Russian matryoshka dolls. But unlike the counting contest, this game is a memory challenge. The sentence never has to end, but eventually your memory will fail, and then you’re out of the game.

Russian Matryoshka dolls

Recursion enables us to place one sentence inside another.

Noted linguist Noam Chomsky maintains that recursion is the key characteristic that distinguishes human languages from animal communication systems. More specifically, he proposes that a genetic mutation transformed the pre-human brain into a recursive thinking machine. This mutation then spread quickly through the population in a few generations.

The first evidence for a language gene came in 1990, when linguist Myrna Gopnik reported on the so-called KE family living in London. Some members of this family exhibit an extreme form of specific language impairment. This is a communicative disorder that can’t be attributed to brain damage, hearing loss, or other causes.

Researchers identified the responsible gene as FOXP2. Family members with normal language abilities had the normal version of FOXP2, while those with specific language impairment had a defective version of the gene.

FOXP2 is widely found among vertebrates, and it plays a role in brain development as well as serving other functions. In songbirds, for example, a mutation of FOXP2 disrupts the ability to learn songs, while in newborn mice it interferes with their ability to call for their mother when they fall from the nest. These observations suggest that FOXP2 plays a role in social communication across a wide variety of species.

Pakastani Sparrow

Gene mutation and the disruption of the learning of birdsong.

In the end, FOXP2 probably isn’t the language gene Chomsky proposed. A closer examination of the KE family shows that their language impairment isn’t so much about syntax—and certainly not about recursion. Rather, their impairment leads to poor articulation, and they tend to leave out unstressed grammar words (like the and of) and hard-to-hear suffixes (like s and ed), much as young toddlers do.

This discussion about the role of FOXP2 provides a good lesson in the proper way to think about genetics. That is, genes code for the production of proteins, and these can have cascading effects during both embryonic development and the entire lifespan of the organism. FOXP2 influences not only the development of neural structures but also the cartilage and connective tissue of the face. All of these are important for spoken language, but they serve other functions as well.

In short, there’s no such thing as a “language gene.” Instead, our ability to speak is certainly influenced by many genes, each of which also serves other functions besides language.

References

Bolhuis, J., Okanoya, K., & Scharff, C. (2010). Twitter evolution: Converging mechanisms in birdsong and human speech. Nature Reviews: Neuroscience, 11, 747–759.

Chomsky, N. (2011). Language and other cognitive systems. What is special about language? Language Learning and Development, 7, 263–278.

Gopnik, M. (1990). Feature-blind grammar and dysphasia. Nature, 344, 715.

Hauser, M. D., Chomsky, N., & Fitch, W. (2002). The faculty of language: What is it, who has it, and how did it evolve? Science, 298, 1569–1579.

Shu, W., et al. (2005). Altered ultrasonic vocalization in mice with a disruption in the Foxp2 gene. Proceedings of the National Academy of Sciences USA, 102, 9643–9648.

Theißen, G. (2006). The proper place of hopeful monsters in evolutionary biology. Theory in Biosciences, 124, 349–369.