My latest Mind and Matter column in the Wall Street Journal:
Three years ago Queen Elizabeth II asked a group of speech therapists if her father's stutter had been caused by his being forced to write with his right hand despite being a natural left-hander. Though it's a more plausible theory than movie psychobabble about conflict with a domineering father (a theme of Oscar front-runner "The King's Speech"), the experts told the queen that this commonly held explanation for stuttering remains unproven. It may be just an urban legend, based on the fact that stuttering is more common among the left-handed.
The connection between handedness and speech runs deep. Speech is controlled by the left side of the brain and so is motor control of the usually dominant right hand. It is possible that this connection says something about the evolutionary origin of language, if language was first expressed through gestures rather than speech.
Curiously, stuttering is not really a speech disorder. Some deaf people stutter in sign language, too. This is just one of the ways that sign language shares all the characteristics of spoken language. For example, in Britain and many other countries-less so in America-sign language has wildly different dialects in different regions. Most hearing people wonder why sign language is not internationally standardized. Answer: for the same reason spoken language is not standardized. Language is an evolved, not an ordained, order.
Indeed, it's probably harder for signers than for speakers to homogenize grammar and vocabulary; they lack radio and TV and are often isolated in a sea of speakers. Simple sign languages become spontaneously more sophisticated when deaf children come together, because they impose grammar on new vocabulary in a way adults don't. In one striking case, the formation of a new school for deaf children in Nicaragua in the 1970s led to a new form of sign language, complete with its own grammar.
Even more remarkably, a Bedouin village in Israel where 5% of the population is genetically deaf because of a mutation in one of its founders has invented its own sign language, which is used by hearing people, too.
If we all learned sign language from birth, there would be some obvious advantages. At loud parties, on trains or during ambushes, we could resort to signing, instead of having to shout, distract fellow travelers or alert our quarry.
So we are all natural signers. Does this indicate that signing was how we all used to communicate? It looks as if our prehuman ancestors had only a modest vocabulary of shouts, screams and whines, but a richer and subtler vocabulary of gestures, shrugs and frowns. According to the primatologist Frans de Waal, apes, especially bonobos, use gestures more freely and flexibly than voice. According to another primatologist, Richard Byrne, gorillas have a large repertoire of gestures used to express specific meanings in the wild. And it appears that chimps learn a vocabulary of signs more easily than a vocabulary of sounds.
But perhaps the most intriguing connection is anatomical. The part of the brain that handles language is right in the middle of the human motor cortex. The ancestral vocalization module lies elsewhere, nearer the crown of the head, which fits with the fact that the ability to swear with gusto sometimes survives intact in stroke victims who otherwise can't speak and also in those who stutter-as the streams of profanity in "The King's Speech" illustrate.
As is often true in evolutionary theory, it's hard to know how to test the idea that signing came first. Speech itself, after all, is a form of gesture, with the lips and tongue, so no wonder it resides in the motor cortex.
And the extraordinary facility human beings have for learning sign languages as well as spoken languages does not necessarily imply an ancestral connection. We also have a great facility for learning written language, which arrived late in human history and thus cannot be an instinct. Verdict: unproven, like the queen's hand-forcing theory of stuttering.