How Can Humans Talk?

The first concrete evidence of a genetic link to the evolution of language in humans was published today in the journal Nature. Researchers led by UCLA neurogeneticist Daniel Geschwind have shown that two small differences between the human and chimpanzee versions of a protein called FOXP2 result in significant differences in the behavior of dozens of genes in human neurons.

FOXP2 is a protein known as a transcription factor; its role is to turn other genes off or on. Geschwind and his collaborators deleted the native gene for FOXP2 from a lab-grown line of human neurons. They then inserted either the gene for human or chimp FOXP2 into the cells and screened the cells to see which genes were being expressed, or actively producing proteins. The researchers identified dozens of genes that were expressed at either higher or lower levels depending on whether the cells were making human or chimp FOXP2. They verified these findings by examining gene expression patterns in post-mortem brain tissue from both chimps and humans who died of natural causes.

Geschwind says that the new study demonstrates that the two mutations believed to be important to FOXP2’s evolution in humans change not only how the protein looks but also how it works, resulting in different gene targets being switched on or off in human and chimp brains. “Our findings may shed light on why human brains are born with the circuitry for speech and language and chimp brains are not,” Geschwind said in a UCLA press release on the research.

Geschwind and other scientists have been studying FOXP2’s role in the development of language since the gene’s discovery in 2001. Jon Cohen reported on some of Geschwind’s ground-breaking research on the genetics of language in the January 2008 issue of Technology Review.