The Gestural Origins of Language
Human language may have evolved from manual gestures, which survive today as a "behavioral fossil" coupled to speech
Freedom of Hand
Nonhuman primates are nevertheless restricted in the use of the hands for communication, since the hands and arms are also critically involved in postural support and locomotion. Most primates are adapted to life in the trees, using their arms for holding onto branches and for swinging from branch to branch. The larger-bodied apes are more terrestrial but move in four-legged fashion over open terrain. Chimpanzees and gorillas, our closest relatives among the primates, adopt a form of locomotion known as knuckle walking, in which the upper body is supported by the knuckles. In contrast, a primary characteristic of the hominid line (going back at least 4 million years) is bipedalism, involving an upright stance in which the hands and arms are largely freed from any involvement in posture or locomotion. This would surely have given a significant boost to their use for a variety of other activities, including expressive communication. Just why bipedalism evolved has been a matter of much speculation. Among the suggested advantages that may have led to its selection are the freeing of the hands for tool use or for carrying things, but expressive communication may have also played a pivotal role.
The split between the hominids and the great apes may have been forged by the formation of the Great Rift Valley in Africa. The apes that were to become hominids were largely confined to the east of this valley. The recent discovery of a 3.5-million-year-old australopithecine fossil in Chad, which is well to the west of the valley, has raised some doubts about the so-called "East-Side Story." Nevertheless, all other hominid fossils dated from just over 4 million to just under 2 million years ago have been found to the east, where forested areas gave way to open savanna-like territory. In this environment the early hominids would have been especially vulnerable to attack from much more specialized and effective hunters and killers, the precursors of modern tigers, lions and hyenas. This may have led to selection for enhanced social cooperation and cohesiveness, in which efficient communication would have been especially important.
In such an environment, gestural communication would be much more effective than vocal communication. First, it is silent, so there is little risk of alerting predators or prey to one's presence. Gesture allows stealth. Second, it is fundamentally spatial, and much of the information to be communicated would be spatial, such as the whereabouts of dangerous predators, easy prey or carcasses to be scavenged. It may be that pointing was among the earliest communicative gestures on the savanna. Indeed, young children learn to point very early on in development, whereas other primates never point. Merlin Donald of Queens University in Kingston, Ontario, has suggested that early communication was based on mime, involving the whole body rather than just the hands and arms, and lives on in modern dance and "body language." Donald's view is that this form of communication is distinct from language, whereas my own view is that it was a precursor. Whatever the case, there is little question that gestural language is more iconic than vocal language. That is, gestural language more directly captures the actual shapes of things and their dispositions in space. Given the preadaptation to voluntary control of the upper limbs and to the mapping of manual action onto the perception of action, it would have been natural for our early ancestors to develop gesture rather than vocalization for the purposes of intentional communication.
If the earliest language were indeed gestural, this would help to explain one of the mysteries of the evolution of speech: how words came to represent objects and events in arbitrary fashion. Words are abstract rather than iconic. With very few exceptions, such as onomatopoeic words like "buzz" or "shriek" or Tennyson's "murmuring of innumerable bees," there is nothing in the actual sound of a word that gives a clue as to its meaning. It has been argued that the earliest words did in fact mimic their referents, a notion pejoratively dubbed the "bow-wow theory" by the 19th-century Oxford philologist Max Müller. But this is regarded as rather implausible, not least because spoken language is unidimensional, structured in time and not space, whereas critical events in our world are four-dimensional, structured in time and space. This restriction does not apply to manual gestures, which might well have emerged from early attempts to physically mimic the physical world. But what may have begun as an iconic system could plausibly have evolved more abstract properties over time, and at some point arbitrary patterns of sound may have been linked to gestures that may themselves have become abstract symbols rather than icons.