The rise and fall of the third chimpanzee

have conceived and built Chartres Cathedral—or V-2 rockets. For these reasons, I speculated in Chapter Two that the Great Leap Forward (the stage in human history when innovation and art at last emerged) was made possible by the emergence of spoken language as we know it. Between human language and the vocalizations of any animal lies a seemingly unbridgeable gulf. It has been clear since the time of Darwin that the mystery of human language origins is an evolutionary problem: now was this unbridgeable gulf nevertheless bridged? If we accept that we evolved from animals lacking human speech, then our language must have evolved and become perfected with time, along with the human Pelvis, skull, tools, and art. There must once have been intermediate language-like stages linking monkey grunts to Shakespeare's sonnets. Darwin diligently kept notebooks on his children's linguistic development, and reflected on the languages of'primitive' peoples, in the hope of solving this evolutionary mystery.

Unfortunately, the origins of language prove harder to trace than the origins of the human pelvis, skull, tools, and art. All of the latter may persist as fossils that we can recover and date, but the spoken word vanishes in an instant. In frustration, I often dream of a time machine that would let me place tape-recorders in ancient hominoid camps. Perhaps I would discover that australopithecines uttered grunts little different from those of chimpanzees; that early Homo erectus used recognizable single words, progressing after a million years to two-word sentences; that Homo sapiens before the Great Leap Forward became capable of strings of words that were longer but still without much grammar; and that syntax and the full range of modern speech sounds arrived only with the Great Leap.

Alas, we have no such retrospective tape-recorder, and no prospects for ever getting one. How can we hope to trace speech origins without such a magic time machine? Until recently, I would have said that it was hopeless to do more than speculate. In this chapter, however, I shall try to draw on two exploding bodies of knowledge that may allow us to begin building bridges across the gulf between animal and human sounds, by starting from each of its opposite shores. Sophisticated new studies of wild animal vocalizations, especially those of our primate relatives, constitute the bridgehead on the animal shore of the gulf. It has always been obvious that animal sounds must have been precursors of human speech, but only now are we beginning to sense how far animals have come towards inventing their own 'languages'. In contrast, it has not been clear where to locate the bridgehead on the human shore, since all existing human languages seem infinitely advanced over animal sounds. Recently, though, it has been argued that a numerous set of human languages neglected by most linguists truly exemplifies two primitive stages on the human side of the causeway.

Many wild animals communicate with each other by sounds, of which bird-songs and the barking of dogs are especially familiar to us. Most ot us are within earshot of some calling animal on most days of our lives. Scientists have been studying animal sounds for centuries. Despite this long history of intimate association, our understanding of these ubiquitous and familiar sounds has suddenly expanded because of the application of new techniques: use of modern tape-recorders to record animal calls, electronic analysis of the calls to detect subtle variations imperceptible to the unaided human ear, broadcasting recorded calls back to animals to observe how they react, and observing their reactions to electronically reshuffled calls. These methods are revealing animal vocal communication to be much more like language than anyone would have guessed thirty years ago. The most sophisticated 'animal language' studied to date is that of a common, cat-sized African monkey known as the vervet. Equally at home in trees and on the ground in savannah and rainforest, vervets are among the monkey species that visitors to East African game parks are most likely to see. They must have been familiar to Africans for the hundreds of thousands of years that we have existed as the species Homo sapiens. They may have reached Europe as pets over 3,000 years ago, and they certainly have been familiar to European biologists exploring Africa since the Nineteenth Century. Many laypeople who have never visited Africa are still acquainted with vervets from visits to the zoo.

Like other animals, wild vervets regularly face situations in which efficient communication and representation would help them to survive. About three-quarters of wild vervet deaths are caused by predators. If you are a vervet, it is essential to know the differences between a martial eagle, one of the leading killers of vervets, and a white-backed vulture, an equally large soaring bird that eats carrion and is no danger to live monkeys. It is vital to act appropriately when the eagle appears, and to tell your relatives. If you fail to recognize the eagle, you die; if you fail to tell your relatives, they die, carrying your genes with them; and if you think it is an eagle when it is really just a vulture, you are wasting time on defensive measures while other monkeys are safely out there gathering food.

Besides these problems posed by predators, vervets have complex social relationships with each other. They live in groups and compete for territory with other groups. Hence it is also essential to know the difference between a monkey intruding from another group, an unrelated member of your own group likely to push you, and a close relative in your own group on whose support you can count. Vervets that get into trouble need ways of telling their relatives that they, and not some other donkey, are in trouble. They also need to know and communicate about sources of food: for instance, which of the thousand plant and animal species in the environment are good to eat, which are poisonous, and here and when the edible ones are likely to be found. For all these reasons, vervets would profit from efficient ways of communicating about and representing their world. Despite these reasons, and despite the long and close association between vervets and humans, we had no appreciation of their complex world knowledge and vocalizations until the mid-1960s. Since then, observations of vervet behaviour have revealed that they make finely graded discriminations among types of predators, and among each other. They adopt quite different defensive measures when threatened by leopards, eagles, and snakes. They respond differently to dominant and subordinate members of their own troop, differently again to dominant and subordinate members of rival troops, differently to members of different rival troops, and differently to their mother, maternal grandmother, sibling, and unrelated members of their own troop. They know who is related to whom: if an infant monkey calls, its mother turns towards it, but other vervet mothers turn instead towards that infant's mother to see what she will do. It is as if vervets had names for several predator species and several dozen individual monkeys.

The first clue to how vervets communicate this information came from observations that the biologist Thomas Struhsaker made on vervets in Kenya's Amboseli National Park. He noted that three types of predator triggered different defensive measures by vervets, and also triggered alarm calls sufficiently distinct that Struhsaker could hear the differences even without making any sophisticated electronic analysis. When vervets encounter a leopard or any other species of large wild cat, male monkeys give a loud series of barks, females give a high-pitched chirp, and all monkeys within earshot may run up a tree. The sight of a martial or crowned eagle soaring overhead causes vervets to give a short cough of two syllables, whereupon listening monkeys look up into the air or run into a bush. A monkey who spots a python or other dangerous snake gives a 'chuttering' call, and that stimulates other vervets in the vicinity to stand erect on their hind legs and look down (to see where the snake is). Beginning in 1977, a husband-and-wife team named Robert Seyfarth and Dorothy Cheney proved that these calls really had the different functions suggested by Struhsaker's observations. Their experimental procedure was as follows. Firstly, they made a tape-recording of a monkey jiving a call whose apparent function Struhsaker had observed (say, the'leopard call'). Then, on a later day, after locating the same troop of monkeys, either Cheney or Seyfarth hid the tape and loudspeaker equipment in a bush nearby, while the other started filming the monkeys with a cine or video camera. After fifteen seconds, one of the two scientists broadcast the tape while the other kept filming the monkeys for one minute to see whether the monkeys behaved appropriately for the call's suspected function (for example, whether the monkeys ran up a tree on hearing a broadcast of the supposed 'leopard' call). It turned out that playback of the 'leopard call' really did stimulate the monkey to run up a tree, while the 'eagle call' and 'snake call' similarly stimulated monkeys into behaviour that seemed to be associated with these calls under natural conditions. Thus, the apparent association between the observed behaviour and the calls was not coincidental, and the calls did have the functions suggested by observation. The three calls that I have mentioned by no means exhaust a vervet's vocabulary. Besides those loud and frequently given alarm calls, there appear to be at least three fainter alarms that are given less frequently. One, triggered by baboons, causes listening vervets to become more alert. A second, given in response to mammals like jackals and hyenas that prey on vervets only infrequently, causes the monkeys to watch the animal and perhaps move slowly towards a tree. The third faint alarm call is a response to unfamiliar humans and results in the vervets quietly moving towards a bush or the top of a tree. However, the postulated functions of these three fainter alarm calls remain unproven because they have not yet been tested by playback experiments.

Vervets also utter grunt-like calls when interacting with each other. Even to scientists who have spent years