Talking From Hand to Mouth

One chimp sits on the ground, contentedly eating fruit in her natal African forest. As she does, a second, younger chimp approaches, but not too close, and extends her hand in a cupping gesture. She is asking the first chimp to share the food. Another chimp, this one at a research center outside Atlanta, eyes a banana just beyond reach, outside and to the left of his cage. When a scientist approaches, the chimp gestures with his right hand, extending it in what's called a whole-hand point, looking back and forth between the scientist and the banana: would you mind passing the chow, big guy?

OK, as language goes, neither cupping the hand nor extending it is exactly Hamlet's soliloquy. The primitive nature of chimp communication has convinced many scientists that our closest living relatives cannot master true language, with all its grammatical twists and syntactical turns. But even these critics admit that what a chimp does, both in the wild and in the lab, at least qualifies as intentional communication. And now they are paying closer attention to the medium of these messages: for although chimp calls indicate emotions like fear and anger, it is chimp gestures that communicate meaning. Combined with studies of deaf-mute children who spontaneously create their own complex, grammatical sign languages--and the finding that blind people gesture at the same rate as sighted people--evidence has been growing that the human brain is wired for gestural communication. Now some linguists are going even further. One of the deepest mysteries in anthropology is when and how language, considered the crowning achievement of human evolution, and the gift that separates our species from all others, originated. An answer may be emerging. "Language may have evolved not from the vocalizations of our ancestors but from manual gestures," says Michael Corballis, a cognitive neuroscientist at the University of Auckland in New Zealand who describes the new research in the current issue of American Scientist.

The notion that human language grew out of gestures was proposed as long ago as the 17th century and was revived in the 1970s. But it foundered for lack of evidence. Now, though, scientists have 20 years' worth of discoveries on how proficient chimps are at sign language. In the wild, a male pygmy chimp (or bonobo) uses hand gestures to indicate to a female how he would like her to position herself for sex, explains chimp-language researcher William Hopkins of Berry College in Georgia and Yerkes Regional Primate Research Center. Bonobos also use hand signals to warn each other that a human observer is lurking. And one young bonobo has been seen making a hand gesture inviting his baby brother to play, rather than scampering around to show through acting out what he has in mind. It may not be language, but it is symbolic communication.

Chimps get to really strut their verbal stuff when they learn American Sign Language (ASL), the hand symbols used by the deaf. Although the apes can't seem to get beyond the language proficiency of a human 2-year-old, there are hints that their facility with gesture "taps into an atavistic neurological system for communication based on gesture," says Hopkins. The chimps easily learn hundreds of ASL signs, and combine them into sentences they have not seen before, along the lines of "tickle me" or "give banana." In another provocative finding, the chimp Washoe, who learned ASL, spontaneously taught it to her adopted son Loulis, who had never seen humans sign, by gently molding his hand to make each sign correctly. Loulis can now use some 80 signs--for objects like bananas and actions like give and come. Although chimps do not show a preference for using one hand over another in most activities, language seems to be different. In a 1998 study of 115 chimps at Yerkes, Hopkins and David Leavens of the University of Georgia found that the chimps were more likely to use their right hand to make meaningful gestures of the please-pass-the-banana kind, even when the banana was on the chimp's left side. "The chimp would use his left hand to reach for the banana," says Hopkins. "The fact that they are using the right hand to make the gesture suggests that this is an attempt to communicate, not reaching." The left side of the brain sends signals to the right side of the body, and also houses the language centers. The use of the right hand to gesture is therefore more support for the idea that the movements are linguistic. "It is possible that these brain areas for language [which were discovered in chimps only last year] are associated with gestural communication," says Hopkins.

The other sea change in the study of gesture is that signing is now recognized "as a proper, grammatical language," as Mike Corballis puts it. It distinguishes between "I showed the cat a dog" and "I showed the dog a cat"; it has tense and case. Moreover, deaf people throughout the world and throughout the centuries have invented sign languages. These systems are fully grammatical, too. Their spontaneous emergence, says Corballis, "confirms that gestural communication is as natural to the human condition as is spoken language." Deaf children even "babble" in sign, making the same gesture over and over just as their hearing friends make the same "ma-ma-ma" over and over.

Deaf children can even invent grammar more sophisticated than that in spoken language. Take the deaf toddlers of hearing parents in China and in the United States who invented sign languages. Their inventions resembled each other more than they resembled the simple signing they saw their parents do, according to a 1998 study led by psychologist Susan Goldin-Meadow of the University of Chicago. In addition, the children's language showed a grammar more sophisticated than appears in either English or Mandarin: the children used a slightly different sign for "mouse" in the sentence "the mouse goes in the hole" than in the sentence "the mouse ate the cheese." The only difference between the statements, for anyone who's forgotten grade-school grammar, is that the first mouse is the subject of a sentence with an intransitive verb ("goes") while the second mouse is the subject of a sentence with a transitive verb ("ate"). Might gesture, then, tap into the same brain structures for grammar that speech does? Brain-imaging studies suggests it does. The clutches of neurons called Broca's and Wernicke's areas, which are responsible for producing and comprehending language, become active when a deaf signer watches sentences in American Sign Language, finds Helen Neville of the University of Oregon.

The idea that the brain harbors ancient systems for grammatical, gestural language comes as no surprise to scientists who study language development in children. Babies make complex gestures before they speak, "and kids who make referential gestures early speak early, while kids who gesture late speak late," explains developmental psychologist Elizabeth Bates of the University of California, San Diego. "Gesture and language share a common neural substrate. This is consistent with the idea that vocal language grew out of gestural language, though it is also consistent with them developing side by side."

It makes sense that our ancestors, in a world of predators, evolved the ability to communicate silently. But not everyone agrees that language originated in gesture. Neuropsychologist Merlin Donald of Queens University in Ontario argues that, if it did, then a fully developed gestural language would still be around; except among the deaf, it isn't. Still, a gestural origin could solve one of the most challenging puzzles in human evolution. Speech, according to fossils of the vocal tracts of human ancestors, arose no earlier than 150,000 years ago. From then until the first ancient civilizations 5,000 years ago or so is, argues Mike Corballis, "an awfully short time for complex things like grammar [that require evolutionary changes in the brain] to have emerged." But if our ancestors had already invented grammar, and used it for gestural language, then transferring that grammar to speech would not have been much harder than applying the lessons of Spanish grammar to Portuguese. Switching mediums was easy. As a result, as soon as the larynx was in place, humans could begin chattering away. They've never stopped.

'Come eat'; 'You eat'; 'Yeah you'

'Come eat' The child jabs his fingers toward his mouth in a 'pointed-O hand-shape,' signaling that he wants someone to join him in eating a snack

'You eat' This signals the particular person with whom he wants to share the snack. He's actually gesturing 'Eat you,' which translates to 'You eat' in English.

'Yeah, you' The child reinforces his choice of snack sharer. Although he's now pointing with his index finger, and not his whole hand, the message is the same.
Comments