The evolutionary miracle of language

Language is widely believed to be unique to humans. Other animals may coo, moo, squeak, sing, even chatter, but they do not seem to possess language as we know it. There is no sense they can tell what they did yesterday or what they might do tomorrow, or tell stories and gossip about each other. Their communications seem to have no grammar, and highly limited repertoires.

In contrast, human language is infinitely diverse, in that there seems no limit to the number of utterances we can generate. The capacity for language is universal among our species, yet there are some 6000 different languages in the world, each more or less impenetrable to the others, and any child could learn any one of them, if exposed early enough. These remarkable properties encourage the belief that language is a miracle, perhaps a gift from God.

The Old Testament says that language was a gift to Adam. The people then built the Tower of Babel, but the Lord thought they had grown arrogant and smashed the Tower, scattering the people, who went on to create multiple languages. This is remarkably similar to the account given by Noam Chomsky, regarded by some as the foremost intellect of our time, who proposed that language emerged in a single step, even in a single individual, within the last 100,000 years, well after the first humans actually walked the planet. Chomsky calls this promiscuous individual Prometheus, rather than Adam. Nevertheless, his account seems to echo the biblical story, although he does not refer to a deity.

Such accounts don’t make much evolutionary sense. According to Darwin, complex functions like language must have evolved in small steps. The miraculous scenarios painted by the Bible, or by Chomsky, also overlook the fact that our common ancestry with the great apes goes back some six million years, which is plenty of time for gradual, stepwise evolution. Sadly, all our hominin forebears are no longer with us, so we have to make educated guesses as to how language might have emerged — there are no Neanderthals or Homo erectus to inform us.

One scenario, which is evolution-friendly and does not imply a miracle, is that language evolved, not from vocal sounds, but from bodily gestures. We now know that great apes, our closest living nonhuman relatives, communicate in more language-like ways using gestures than in making sounds. Their calls tend to be fixed and inflexible compared with their bodily movements. There has been no success in teaching chimpanzees, bonobos or gorillas to talk, but they can learn to communicate in language-like fashion using simplified sign language, or pointing to symbols on a specially designed keyboard.

After splitting from the line leading to modern great apes, our hominin forebears probably developed a form of pantomime, especially as they moved from forested environment and adapted to hunter-gatherer and migratory patterns of living. Pantomime seems a natural way to share information about past travels or future plans. It probably co-evolved with the upright, bipedal stance, freeing the arms and upper body for greater variety of expression. I think we all resort to pantomime when we visit a foreign country and don’t know the local lingo.

But pantomime can be clumsy and inefficient, and over time probably became simplified and “conventionalised,” gradually losing its pictorial or iconic character. Sign languages have all the sophistication of spoken languages, but they too lose their pantomimic quality and become more arbitrary over time, carried by social convention rather than resemblance to what is conveyed.

Speech can be seen as the end product of this progression toward conventionalisation and arbitrariness. Like the hands, the mouth is also flexible and capable of generating voluntary signals, and requires much less energy than pantomime. The mouth also includes internal parts—tongue, larynx and pharynx—that are invisible, but mouthed signals can be made perceptually accessible through adding sound, which is modulated by internal gestures to create distinctive sound patterns. This is speech, itself a gestural system, tucked into the mouth, with the added advantage that it frees the hands for other things, like making and using tools, or carrying things. Speech is an early example of miniaturisation.

The move toward arbitrariness also means that language becomes a barrier to communication as well as a vehicle for it. Different cultures create different languages to maintain communication within, but deny it to outsiders. Language is at once a social and religious facilitator and a barricade.

The argument for the gestural origins was boosted by the discovery of a network in the monkey brain that was active, both when the monkey made a grasping movement, say to pick up a grape, and also when it watched another individual making the same movement. This “monkey see, monkey do” system is known as the mirror system, and seems to form a natural platform for the later evolution of language itself. It does not respond to voiced sounds in the monkey, which lends support to the idea that language started out as a gestural system.

Brain imaging shows that humans also house a mirror system, and our own work suggests that it is divided into at least three different networks. One remains dedicated to simple gestures, as in monkeys, one is associated with hand preference and probably adapted to tool use, and the third courses through auditory regions and is activated by speech. The last two are biased toward the left brain in most people. There may well be other networks deriving from the mirror system that are biased in the other direction.

A shift from gesture to speech was just the first step in the evolution of communication. Pictorial representation, such as cave drawings, may have followed when speech freed the hands, and then advanced with writing, the printing press, telephone, radio; on to the Internet and the cell phone. And with these developments, where we have fingers flicking over small keyboards, we are seeing something of a resurgence of gesture and bodily movements in our modern forms of human communication.

Spring week lectures

Emeritus Professor Corballis is presenting a lecture on the theme of language during Spring Week on Campus at 10am on November 21.

Spring Week on campus is an annual event that gives the public a rare opportunity to listen to, debate and engage with the university’s world-class academics. Morning and afternoon lectures will be held every day between November 19 to 23 to celebrate Spring and the birth of new knowledge and ideas.