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The genetic changes underlying the evolution of language in humans remain mysterious. FOXP2 is the only gene to be linked so far to inherited speech and language dysfunction — prompting researchers to probe its evolutionary significance. On page 213, Daniel Geschwind of the University of California, Los Angeles, and his colleagues express the human and chimpanzee versions of FOXP2 in human brain cells to compare their activities. Geschwind talks to Nature about what they found.

How did this work come about?

My lab is interested in understanding what makes humans human. We study the genetic basis of language both in health and in diseases such as autism and neurodegeneration. In this study, we tried to combine a hypothesis-driven study to learn more about the specific functions of a known gene with discovery-based science that might help to identify an evolutionary context for its function.

Did the work shed light on the differences between chimpanzees and humans?

Yes. We found that not only FOXP2, but also some targets of the FOXP2 protein, may be co-evolving in humans. We first introduced the human and chimpanzee versions of FOXP2 in cell culture and looked at which genes were turned on as a result, then we compared the patterns of gene expression with those normally seen in adult brain tissue from humans and chimpanzees. We found that a significant proportion of FOXP2's targets that were different between chimpanzees and humans in cell culture were also different between the chimpanzee and human brain.

So, is there much doubt that FOXP2 is central to language evolution?

The high correlation between FOXP2 targets and the differences observed between chimpanzee and human brains does suggest an important role. FOXP2 is probably part of a larger regulatory network. For example, FOXP2 also regulates another gene involved in language and autism, CNTNAP2. Our work also raises the possibility that FOXP2 regulates the development of some key motor and physical structures that are important for speech — such as the larynx and pharynx.

Is mixing hypothesis-based and discovery-based science typical in this field?

Neuroscience is traditionally a hypothesis-driven field. By combining hypothesis testing with discovery-based methods, we can more quickly make progress in understanding what is happening at multiple levels — from molecules to cells to circuits and to behaviour.