University of Auckland

abstract

True language appears to be unique to humans. This has created severe problems in understanding how it evolved, since there is little that can be learned about its evolution from the communications of other species. Attempts at explanation have therefore depended more on speculation than on fact, prompting the Linguistic Society of Paris, as early as 1866, to ban all discussion of the language origins. Moreover, given that spoken language is based on abstract symbols (words), it is not clear how it began: How was it decided which symbols would stand for which concepts, and how was this propagated? As Rousseau remarked, "Words would seem to have been necessary to establish the use of words." I shall argue that this apparent paradox can be at least partially resolved if it is supposed that language evolved from manual gestures, since gestures have at least the potential to represent concepts iconically rather than in abstract form. Once a set of iconic representations is established, increasing usage can then lead to more stylized and ultimately abstract representation, as has occurred in the evolution of writing systems.

Manual and bodily gestures play a prominent part in contemporary language. The work of David McNeill and his colleagues at the University of Chicago have documented the role of gestures in present-day spoken language, and shown that gestures take on syntactic structure if people are prevented from speaking. A number of societies, notably certain groups of aboriginal people in Australia and the United States, have developed sign languages that can function in the absence of speech. The most accessible sign languages, however, are those invented by deaf communities, and these are clear examples of purely gestural language that have all of the important hallmarks of true language, including fully developed syntax. Children learning sign language from infancy go through essentially the same developmental stages as those learning to speak, and sign language also appears to be predominantly left-hemispheric.

Primates, including ourselves, are predominantly visual creatures, with excellent voluntary control over the muscles of the limbs, while in nonhuman primates control over vocalization is relatively poor and is largely emotional rather than voluntary. The vocal and auditory systems system in primates are better adapted to an arousing or alerting function than to a descriptive or narrative one. Where the intent is to convey information about a four-dimensional world of space and time, as is the case in human language, the early hominids were surely better preadapted to use gestures, which permit four-dimensional representation, rather than vocalization, which is essentially restricted to the single dimension of time. As evidence for this, there has been at least some measure of success in teaching a form of sign language to chimpanzees and gorillas, whereas attempts to teach them to speak have been fruitless. Moreover, it has recently been discovered that there are neurons in the prefrontal cortex of macaques that respond both when the animal makes a specific grasping movement, and when it observes the same grasping movement made by others. These so-called "mirror neurons", it has been suggested, may represent a precursor to a gestural language. They may also relate to an ability to take the mental perspective of others, which can be regarded as a necessary precursor to language.

The hominids split from the precursor of the modern chimpanzee about five million years ago. The main characteristic distinguishing the hominids was bipedalism, whereas the common ancestor was presumably a quadrupedal knuckle walker, as are present-day chimps and gorillas. Bipedalism freed the hands and arms from any major role in locomotion, and created a more frontal stance, both of which would have boosted a gestural, visual form of communication. It is conceivable that gestural communication was a factor in the selection of the bipedal stance, and not simply a fortuitous consequence of it. These early hominids lived on the savanna-like territory, mostly to the east of the Great Rift Valley in Africa, and an effective, silent form of communication may have been crucial to survival in a habitat populated by dangerous killers, such as the precursors to modern tigers, lions, and hyenas.

About two million years ago, at least one branch of hominids, now called hominins, began to show new characteristics. These included increased brain size, the emergence of manufactured stone tools, and the beginnings of migrations from Africa into Asia and Central Europe. I shall argue that these developments may have heralded the emergence of a more sophisticated language, still probably mainly gestural, but including a recursive syntax that enabled communication to be generative. It is likely that vocalizations increasingly accompanied gestures, which might explain why cerebral asymmetry links handedness with left-hemispheric control of vocalization.

Recent evidence suggests that modern-day humans evolved from an African branch of hominins some 100-150,000 years ago. This new species, Homo sapiens, also migrated out of Africa, beginning perhaps 70,000 years ago, and eventually replaced all other hominids, including the Neanderthals in Europe and Homo erectus in Java and Southern Asia. What explains the dominance of H. sapiens over equally large-brained hominids like the Neanderthals? I suggest that it was the conversion from a form that was dependent on gestures to one that could function entirely vocally. It presumably took place before H. sapiens migrated from Africa, since present-day humans speak, and it is unlikely that autonomous speech arose independently in different geographic locations. On the other hand, reconstructions of the vocal tract have been interpreted to mean that the Neanderthals would have been incapable of fluent speech. This suggests that the conversion to autonomous speech took place, perhaps gradually, somewhere between about 150,000 and 70,000 years ago. The conversion may have been quite a small step, since vocalizations probably played an increasing role throughout hominid evolution, but it was a crucial step because it freed the hands from communication. This would have enhanced tool manufacture, allowing people to explain techniques verbally while demonstrating them. This may have heralded the beginning of pedagogy. It would also have allowed communication at night, and when obstacles prevent communicating parties from viewing each other. It also places fewer demands on focal attention.

I suggest that the emergence of sophisticated tools, art, ornamentation, and human culture can be attributed to the emergence of a fully autonomous vocal language. There was a particularly dramatic increase in the sophistication of human artifacts around 30-40,000 years ago, which is perhaps too late to be attributed directly to the emergence of autonomous vocal language some 60-100,000 years earlier. However, recent evidence suggests that this so-called "evolutionary explosion" may have occurred much earlier in Africa, and earlier migrations, such as that to Australia, must have required sophisticated technology. I suggest that, with the switch to vocalization, technology and social complexity progressed in exponential fashion, and shows no signs of abating. One of the consequence of the freeing of the hands was the development of new visual forms of communication, including pictorial art, writing, and ultimately photography, film, and computer graphics. So we come back to ways of exploiting the visual sophistication that we inherited from our primate forbears.

The idea that language evolved from manual gestures is not new. It was suggested in 1746 by the philosopher Condillac, and was revived in the 1970s by the anthropologist Gordon W. Hewes. It received something of a boost, notably from the linguist William Stokoe, when it was fully understood that the sign languages of the deaf have all of the essential hallmarks of true language, including generative syntax. A number of linguists and anthropologists have supported the idea, but on the whole it has not been widely accepted. For example, one of the most popular and influential of recent books on language, Steven Pinker’s The Language Instinct, essentially dismisses the idea, despite the fact that it includes examples from sign language to support ideas about the development and nature of language. I believe the idea is now sufficiently compelling that it should be taken seriously.

 Conference site: http://www.infres.enst.fr/confs/evolang/