RENEE MONTAGNE, host:
Scientists are finding clues to the nature of human speech in a surprising place: the genetic code of a small, noisy songbird. The bird is a zebra finch. As NPR's Jon Hamilton reports, the genes that help these finches learn to sing have a lot in common with the genes we use to acquire language.
JON HAMILTON: The zebra finch is the second bird to have its entire genome sequenced. The first was the chicken. But David Clayton from the University of Illinois says you can't find out much about human speech from a chicken.
Dr. DAVID CLAYTON (University of Illinois): The clucks that they make are not learned. They don't have to hear any other bird to learn how to do that cluck.
HAMILTON: On the other hand, Clayton says male zebra finches have a very sophisticated song that they have to learn.
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HAMILTON: Clayton says a young male zebra finch learns to sing much the way a child learns to talk.
Dr. CLAYTON: The rudimentary steps are very similar in the early learning process. Just like a human infant begins by babbling, the same thing happens with a young zebra finch. He actually begins his singing in a phase that's called subsong, which has been likened to the babbling of a human infant.
HAMILTON: Clayton says the young bird refines this babble into a song by listening to an older male, usually his father.
Dr. CLAYTON: And once he learns that song, it becomes his song, and the same song he sings for the rest of his life without any further change.
HAMILTON: So researchers have been combing the zebra finch genome, looking for genes that seem to play a role in learning songs. Wes Warren from Washington University School of Medicine in St. Louis says they knew they would find some, but the number turned out to be staggering.
Dr. WES WARREN (Washington University School of Medicine): We talk about the whole genome being engaged in the vocal learning process.
HAMILTON: The search turned up more than 800 genes that appear to help create and control special brain circuits involved in learning and singing. Warren says that during the period when a young male finch is developing his signature song, large numbers of these genes get switched on or off in a matter of hours.
Dr. WARREN: And so the sophistication, the speed and the complexity is just amazing to me in this little bird, that you would think this song is very simplistic. But the things going on in the brain are not.
HAMILTON: The intriguing thing about what's going on in the zebra finch brain is how much it resembles what's going on in speech areas of the human brain. Clayton says even though birds diverged from human ancestors more than 300 million years ago, both still seem to rely on many of the same genes for vocal communication.
Dr. CLAYTON: These genes are alive. I mean, they are doing things in the brain whenever you're communicating. In fact, they're probably being turned on in your brain right now as you are listening to me talk and trying to figure out what it is I'm talking about.
HAMILTON: In zebra finches, many of the genes are an unusual type. Their main job seems to be coordinating the activity of other genes. Scientists think this type of gene may also explain why vocal learning is possible in just a few species, including bats, whales, elephants, birds and, of course, people.
Story Landis directs the National Institute of Neurological Disorders and Stroke, which helped pay for the research on the zebra finch genome. She hopes it will help explain some mysterious speech problems that affect people.
Dr. STORY LANDIS (Director, National Institute of Neurological Disorders and Stroke): Quite recently, a group described a gene that causes stuttering in Pakistani families - very surprising discovery.
HAMILTON: And very puzzling. The gene in question doesn't have any obvious connection to speech. But Landis says the connection might become clear if that gene turns out to cause the bird equivalent of stuttering in the zebra finch. The new research appears in the journal Nature.
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HAMILTON: Jon Hamilton, NPR News.
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