Those who advocate the idea that human language has genetic origins will take heart at a new discovery: University of Oxford researchers have pinpointed a genetic mutation that seems to be responsible for a rare speech and language disorder.
Since 1990, scientists have been studying three generations of the "KE" family, many members of which have an inherited language deficit. Those affected have trouble moving their mouth and tongue, identifying the sounds that make up words, and understanding sentences and rules of grammareven though some of them possess normal intelligence. Until recently, no one was able to pin down exactly which gene was at fault. Now Cecilia Lai, Simon Fisher and colleagues, reporting in todays Nature, show that a gene on chromosome 7, which they call FOXP2, is mutated in the affected members of the KE family, as well as in an unrelated patient with a similar language deficit. The gene is normal in the rest of the family and in 364 other unrelated, unaffected people.
Based on studies of other genes related to FOXP2, the authors suggest that the loss of functioning protein from one copy of this gene might disrupt the proper growth of key speech and language structures in the brain. "This is the first gene, to our knowledge...implicated in such pathways," the authors write, "and it promises to offer insights into the molecular processes mediating this uniquely human trait."
In a commentary on the work in the same issue, Steven Pinker, a cognitive scientist at the Massachusetts Institute of Technology, says this "smoking gun for a genetic cause of one kind of language disorder" should motivate researchers to search for possible genetic explanations of cognitive deficits in general, as well as potential treatments. From an evolutionary standpoint, he adds, "comparisons of the gene in humans to those in chimpanzees and other primates...could add to our understanding of how human language evolved.