British scientists have found the first gene related to language, which, they believe, may help explain this unique human ability. In a mutated form, which is what the researchers located, the gene is implicated in a speech disorder.
After an 11-year hunt, researchers at the University of Oxford, England, have found a gene they believe is involved in the development of human speech.
"Our finding is the first gene identified for a speech and language disorder," said Anthony Monaco led the research team, which published its findings in the journal Nature. "This gene," he said, "can take us forward into understanding the developmental pathways underlying speech and language."
Mr. Monaco's group traced the gene in a large family of several generations in which half the members suffer a speech and language disorder. It is the same half that has the mutated version of this gene. They have difficulty moving their tongue, lips, and mouth and make frequent grammatical errors.
Intelligence tests verify that relatives with the disorder have normal or above average intelligence. So the mutated gene seems the culprit.
Mr. Monaco says the gene's normal job is as a master switch that turns other genes on and off. He speculates that it and the genes with which it interacts may be part of a genetic network for language. "We think it's important in brain development, of certain areas of the brain, which are probably involved in the circuitry in the development of language," he said.
Mr. Monaco does not claim, however, these genes are dedicated to speech and language alone. Other experts are also reluctant to acknowledge specific speech and language genes.
University of Iowa speech pathologist Bruce Tomblin agrees that the speech disorder seems to have a genetic cause. But he says the gene and the ones it controls may have additional functions, making it risky to assume they control a special speech and language circuit. "It remains unclear," he said, "whether we would want to say that this is a speech and language gene in that it does appear as though these people had often time probably other problems that may not be solely limited to language."
Emphatic agreement with this view comes from the director of the Center of Language Research at the University of California at San Diego, Elizabeth Bates. She says other studies show that the family with the gene defect has problems with musical pitch and rhythm and with hand movements. To her, this suggests the gene is involved with more than just speech and language.
Ms. Bates also points to monkey and human brain imaging studies that indicate the movement and perceptual systems are linked. "That doesn't mean that language and gesture are the same thing," she said. "They are not. But it suggests that language is overlaid on a more ancient sensory-motor system. And guess what? That system still does the ancient work it did before we had language. So language doesn't own, it rents."
To determine if the gene has a more far-reaching impact on language than just the speech disorder, the University of Oxford's Anthony Monaco is studying its molecular structure to see how far it has evolved from its analog in chimpanzees and other primates. Mr. Monaco said, "Most genes will have changes over millions of years between the species. Since language and speech is a characteristic human behavior, we would want to see if this gene evolved faster in humans than animals."
Mr. Monaco says large differences in the gene between humans and other species would hint that its role changed over time, perhaps to assume speech and language functions.