Finding the brain’s common language
To learn how speech evolved, Erich Jarvis studies the brains of birds such as canaries that can imitate sounds.
Ene/iStockphoto
Erich Jarvis dreams of creating a talking chimpanzee. If his theories on language are right, that just might happen one day.
Jarvis says that the ability to imitate sounds, not higher intelligence, is the key to language. Most animals are born already knowing the calls they’ll croon, but human babies learn words by mimicking how others talk. “I argue it’s what makes spoken language unique,” says Jarvis, a neurobiologist at Duke University Medical Center.
That realization came from an unlikely place: bird brains. Jarvis has spent more than a decade studying the brain circuitry of songbirds, parrots and hummingbirds, which are among the few critters that imitate and learn new vocalizations, a skill called vocal learning. Although humans and birds split evolutionarily from one another more than 300 million years ago, Jarvis and his colleagues have discovered that the brain circuitry for speech and birdsong is remarkably similar.
Humans and vocal-learning birds have networks of neurons that connect analogous brain regions. One of these connections hooks up a brain area related to speaking and singing to neurons in the brain stem that control the muscles of the voice box (called the larynx in humans). Animals incapable of vocal learning don’t have such connections.
These networks, Jarvis says, “are imbedded within a more ancient pathway that controls learning how to move.” He suspects that the crucial moment in the origin of language occurred when a genetic mutation created a new pathway from the brain’s motor-learning region to the vocal organs. This link may allow people to voluntarily control their voice box in the same way they can control their legs while walking or their hands while typing. Speech, then, is just another motor skill, Jarvis says.
Now, he’s working to identify the genes that oversee the development and maintenance of these brain connections. He and his colleagues have already discovered dozens of genes that might play a role. Once the genetics is worked out, Jarvis hopes that researchers can learn to manipulate the genes to repair brain damage in people with speech disorders.
He also wants to use genetic engineering to re-create the brain connections for vocal learning in animals that naturally lack them, such as chimps, to see if he can transform them into vocal learners, he says. “That’s my ultimate goal.”
Song and dance
