The Rise and Fall of the Third Chimpanzee

Parts one and two discussed the genetically specified foundations of our unique cultural traits. We saw that those foundations include our familiar skeletal hallmarks, such as our large braincase and our adaptations for upright gait. They also include features of our soft tissues, behaviour, and endocrinology concerned with reproduction and social organization. But if those genetically specified features were our sole distinctions, we would not stand out among animals, and we would not now be threatening the survival of ourselves and other species. Other animals, such as ostriches, walk erect on two legs. Others have relatively large brains, though not as large as ours. Others live monogamously in colonies (many seabirds), or are very long-lived (albatrosses and tortoises).

Instead, our uniqueness lies in the cultural traits that rest on those genetic foundations and that in turn give us our power. Our cultural hallmarks include spoken language, art, tool-based technology, and agriculture. But if we stopped there, we would have a one-sided and self-congratulatory view of our uniqueness. The hallmarks I just mentioned are ones that we are proud of. Yet the archaeological record shows the introduction of agriculture to have been a mixed blessing, seriously harming many people while benefitting others. Chemical abuse is a wholly ugly human hallmark. At least it does not threaten our survival, as do two of our other cultural practices: genocide, and mass exterminations of other species. We are uncomfortable about whether to regard these as occasional pathological aberrations, or as features no less basic to humanity than the traits we are proudest of.

All of these cultural traits that define humanity are seemingly absent in animals, even in our closest relatives. They must have arisen some time after our ancestors parted company from the other chimpanzees around seven million years ago. Furthermore, while we have no way of knowing whether Neanderthals spoke or indulged in drug abuse and genocide, they certainly did not have agriculture, art, or the capacity to build radios. These latter traits must therefore be very recent human innovations of the last few tens of thousands of years. However they could not have arisen from nothing. There had to have been animal precursors, if we could, only recognize them.

For each of our defining cultural traits, we need to ask, what were those precursors? When in our ancestry did the trait approach its modern form? What were the early stages of its evolution like, and can those stages be traced archaeologically? We are unique on Earth, but how unique are we in the universe?

Our two most dangerous traits, genocide and environmental destruction, will be reserved for discussion in Parts Four and Five. Here we will consider some of the above-mentioned questions for our noble, two-edged, or only mildly destructive characteristics. Chapter Eight takes up the origin of spoken language, which I suggested in Chapter Two might have triggered the Great Leap Forward, and which anyone would list among our most important distinctions from animals. On first reflection, the task of tracing the development of human language appears plainly impossible. Language before the dawn of writing left no archaeological remains, unlike our first experiments in art, agriculture, and tools. There seems to be no surviving simple human language, no animal language, that could exemplify the early stages.

In fact, there are innumerable animal precursors: the vocal communication systems evolved by many species. We are just beginning to appreciate the sophistication of some of these systems. We shall also see that there really are some simple languages that modern humans have unconsciously invented and that prove unexpectedly instructive. Taken together, these complex animal 'languages' and simple human languages begin to bridge, from both sides, the apparent chasm with respect to speech between animals and ourselves.

Chapter Nine turns to the origin of art, the noblest human invention. There seems to be a gulf separating human art, supposedly createdjust for pleasure and doing nothing to perpetuate our genes, from any animal behaviour. Yet paintings and drawings created by captive apes and elephants, whatever the motives of those animal artists, look so similar to work of human artists that they have fooled experts and have been bought by art collectors. If one nevertheless dismisses those animal artworks as unnatural productions, what is one to say about the carefully arranged coloured displays of normal male bowerbirds? Those bowers play an unquestioned crucial role in passing on genes. I shall argue that human art also had that role originally, and often still does today. Since art, unlike language, does show up in archaeological deposits, we know that human art did not proliferate until the time of the Great Leap Forward.

Agriculture, the subject of Chapter Ten, has an animal precedent, but not precursor, in the gardens of leaf-hopper ants, which lie far off from our direct lineage. The archaeological record lets us date our 'reinvention' of agriculture to a time long after the Great Leap Forward, within the last 10,000 years. That transition from hunting and gathering to agriculture is generally considered a decisive step in our progress, when we at last acquired the stable food supply and leisure time prerequisite to the great accomplishments of modern civilization. In fact, careful examination of that transition suggests another conclusion: for most people the transition brought infectious diseases, malnutrition, and a shorter lifespan. For human society in general it worsened the relative lot of women and introduced class-based inequality. More than any other milestone along the path from chimpanzeehood to humanity, agriculture inextricably combines causes of our rise and our fall.

Abuse of toxic chemicals is a widespread human hallmark documented only within the last 5,000 years, though it may well go back much earlier into pre-agricultural times. Unlike agriculture, it does not even rank as a mixed blessing but as a pure evil threatening the survival of individuals, though not of our species. Like art, drug abuse seems at first to lack animal precedents or biological functions. I shall argue in Chapter Eleven, however, that it fits into a broad class of animal structures or behaviours that are dangerous to their owners or practitioners, and whose function depends paradoxically on that danger. While animal precursors can thus be identified for all of our hallmarks, they still rank as human hallmarks because we are unique on Earth in the extreme degree to which we have developed them. How unique are we in the universe? Once conditions suitable for life exist on a planet, how likely are intelligent, technologically advanced life forms to evolve? Was their emergence on Earth practically inevitable, and do they now exist on innumerable planets circling other stars?

There is no direct way to prove whether creatures capable of language, art, agriculture, or drug abuse exist elsewhere in the universe, because from Earth we could not detect the existence of those traits on planets of other stars. However, we might be able to detect high technology elsewhere in the universe if it included our own capacity to send out space probes and interstellar electromagnetic signals. In Chapter Twelve I shall examine the on-going search for extraterrestrial intelligent life. I shall argue that evidence from a quite different field—studies of woodpecker evolution on Earth—instructs us about the inevitability of evolving intelligent life, and hence about our uniqueness, not only on Earth but also in the accessible universe.

EIGHT BRIDGES TO HUMAN LANGUAGE

The gulf between animal vocal communication and human speech has traditionally been viewed as unbridgeable. In fact, recent studies of animal vocalizations show some of them to be far more sophisticated than we had previously suspected. On the other hand, there are dozens of cases in which humans have been forced by exceptional social circumstances to create simplified languages, possibly illustrating two primitive stages in the evolution of human language. Thus, we are beginning to understand how our most unique and important distinction from animals nevertheless arose from animal precursors.

The mystery of human language origins is the most crucial in understanding how we became uniquely human. After all, it is language that allows us to communicate with each other far more precisely than any animal can. Language enables us to formulate joint plans, to teach one another, and to learn from what others have experienced elsewhere or in the past. With it, we can store precise representations of the world in our minds, and hence encode and process information far more efficiently than any animal can. Without language we could never 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 listening to vervets, all these social grunts sound the same. When the grunts are recorded and displayed as a frequency spectrum on the screen of a sound-analysing instrument, they look the same. Only when the spectra were measured in elaborate detail could Cheney and Seyfarth detect (sometimes but not always!) average differences between the grunts given in four social contexts: when a monkey approaches a dominant monkey, when it approaches a subordinate monkey, when it watches another monkey, or when it sees a rival troop. Broadcasts of grunts recorded in these four different contexts caused monkeys to behave in subtly different ways. For example, they looked towards the loudspeaker if the grunt had originally been recorded in the 'approach dominant monkey' context, while they looked in the direction towards which the call was being broadcast if it had originally been recorded in the 'see rival troop' context. Further observations of the monkeys under natural conditions showed that the natural calls had also been eliciting this subtly different behaviour.

Vervets are much more finely attuned than we are to their calls. Merely listening to and watching vervets, without recording and playing back their calls, gave no hint that they had at least four distinct grunts—and may have many more. As Seyfarth writes, 'Watching vervets grunt to ^£ach other is really very much like watching humans engaged in conversation without being able to hear what they're saying. There aren't any obvious reactions or replies to grunts, so the whole system seems very mysterious—mysterious, that is, until you start doing playbacks. These discoveries illustrate how easy it is to underestimate the size of an animal's vocal repertoire.

The vervets of Amboseli have at least ten putative 'words': their words for 'leopard', 'eagle', 'snake', 'baboon', 'other predatory mammal', 'unfamiliar human', 'dominant monkey', 'subordinate monkey', 'watch other monkey', and 'see rival troop'. However, virtually every claim of animal behaviour suggesting elements of human language is greeted with scepticism by many scientists, who are convinced of the linguistic gulf separating us from animals. Such sceptics consider it simpler to assume that humans are unique, and that the burden of proof should be borne by anyone who thinks otherwise. Any claim of language-like elements for animals is considered a more complicated hypothesis, to be dismissed as unnecessary in the absence of positive proof. Yet the alternative hypotheses by which the sceptics instead attempt to explain animal behaviour sometimes strike me as more complicated than the simple, and often plausible, explanation that humans are not unique.

It seems a modest claim to propose that the different calls which vervets give in response to leopards, eagles, and snakes actually refer to these animals or are intended as communications to other monkeys. However, sceptics were disposed to believe that only humans could emit voluntary signals referring to external objects or events. The sceptics proposed that the vervet alarm calls were merely an involuntary expression of the monkey's emotional state ('I'm scared out of my wits! ) or of its intent ('I'm going to run up a tree'). After all, those explanations apply to some of our own 'calls'. If I saw a leopard coming at me, I too might emit a reflex scream even though there was no one around with whom to communicate. We grunt as a reflex when we throw ourselves into some physical activities, such as lifting a heavy object. Suppose that zoologists from an advanced civilization in outer space observed me to give a trisyllabic scream, 'argh, leopard', and to climb a tree, when I saw a leopard. The zoologists might well doubt that my lowly species could express anything beyond grunts of emotion or intent—certainly "not symbolic communications. To test their hypothesis, the zoologists would resort to experiments and detailed observations. If I screamed regardless of whether any other human was in earshot, that would support the theory of a mere expression of emotion or intent. If I screamed only in the presence of another person, and only when approached by a leopard but not by a lion, that would suggest a communication with a specific external referent. And if I gave the scream to my son but remained silent when I saw the leopard stalk a man with whom I had frequently been seen to fight, the visiting zoologist would feel certain that a purposeful communication was involved.

Similar observations convinced earthling zoologists of the communicative role of vervet alarm calls. A solitary vervet chased by a leopard for nearly an hour remained silent throughout the whole ordeal. Mother vervets give more alarm calls when accompanied by their own offspring than by unrelated monkeys. Vervets occasionally give the 'leopard call' when no leopard is present but when their troop is fighting with another troop and losing the fight. The fake alarm sends all combatants scrambling for the nearest tree and thereby serves as a deceptive 'time out'. The call is clearly a voluntary communication, not an automatic expression of fear at the sight of a leopard. Nor is the call a mere reflex grunt given in the act of climbing a tree, since a calling monkey may either climb a tree, jump out of a tree, or do nothing, depending on the circumstances.

The supposition that the call has a well-defined external referent is especially well illustrated by the 'eagle call'. Among large, broad-winged, soaring hawks, vervets usually respond with the eagle call to the martial eagle and the crowned eagle, their two most dangerous avian predators. They usually do not respond to the tawny eagle, and almost never to the black-chested snake eagle and white-backed vulture, which do not prey on vervets. Seen from below, black-chested snake eagles look rather similar to martial eagles in their shared pale underparts, banded tail, and black head and throat. Hence vervets rate as good bird-watchers. Their lives depend on it! Vervet alarm calls are not an involuntary expression of either fear or intent. They have an external referent that may be quite exact. They are finely targeted communications which are more likely to be given honestly if the caller cares about the listener, and which may also be given dishonestly to enemies.

Sceptics dispute proposed analogies between animal sounds and human speech on the additional grounds that human speech is learned, but that many animals are born with the instinctive ability to utter the sounds characteristic of their species. However, young vervets appear to learn how to utter and respond to sounds appropriately, just as human infants. The grunts of an infant vervet sound different from those of an adult. 'Pronunciation' gradually improves with age until it becomes virtually adult at about the age of two years, somewhat less than half the age for vervet puberty. That is like human children attaining adult pronunciation at the age of five years; my sons, who are almost four years °ld, are still sometimes difficult to understand. Infant vervets do not learn ^ro give reliably the correct response to an adult's call until the age of six or seven months. Until then, an adult's snake alarm call may send the infant jumping into a bush, the correct response to an eagle but a suicidal response to a snake. Not until the age of two years does the infant consistently emit each alarm call in the correct context. Before that age, the young vervet may call 'eagle! not only when a martial or crowned eagle goes overhead, but also when any other bird flies over, and even when a leaf flutters down from a tree. Child psychologists refer to such behaviour in our own children as 'overgeneralizing'—as when a child greets not just dogs but also cats and pigeons with 'bow-wow'.

If vervet calls are indeed partly learned rather than entirely instinctive, one might expect vervet populations in different parts of Africa to have developed different 'dialects' for the same reason that different human populations, have. That is, 'word' meanings and pronunciations would gradually change with time, but the changes would develop independently in different areas and would be transmitted by learning, leading first to different dialects and eventually to different languages. This prediction of dialect differences has yet to be tested for vervets, since all the detailed studies of their vocal communication to date have been made in one small area of Kenya. However, song dialects are well developed in some bird species whose young learn the locally correct song from adult birds that they hear around them as they grow up. In a North American songbird called the white-crowned sparrow, such dialect differences are so pronounced that experienced bird-watchers near San Francisco can pinpoint an individual sparrow's home within ten miles.

So far, I have loosely 'applied human concepts such as 'word' and 'language' into vervet vocalization. Let's now compare human vocalizations and those of subhuman primates more closely. In particular, let's ask ourselves three questions. Do vervet sounds really constitute 'words'? How large are animals' 'vocabularies'? Do any animal vocalizations involve 'grammar' and merit the term 'language'?

Firstly, on the question of words, it is clear at least that each vervet alarm call refers to a well-defined class of external dangers. That does not imply, of course, that a vervet's 'leopard call' designates the same animals to a vervet as the word 'leopard' does to a professional zoologist—namely, members of a single animal species, defined as a collection of potentially interbreeding individuals. We already know that vervets give their leopard alarm in response not just to leopards but also to two other medium-sized cat species (caracals and servals). If the 'leopard call' is a word at all, it would not mean 'leopard' but instead 'medium-sized cat that is likely to attack us, hunts in a similar way, and is best avoided by running up a tree'. However, many human words are used in a similar generic sense. For example, most of us other than ichthyologists and ardent fishermen apply the generic word 'fish' to any cold-blooded animal with fins and a backbone that swims in the water and might be worth eating. Instead, the real question is whether the leopard call constitutes a word ('medium-sized cat that… etc. ), a statement ('there goes a medium-sized cat'), an exclamation ('watch out for that medium-sized cat! ) or a proposition ('let's run up a tree or take other appropriate action to avoid that medium-sized cat'). At present it is not clear which of those functions the leopard call fills, or whether it fills a combination of them. Similarly, I was excited when my then one-year-old son Max said 'juice', which I proudly took to be one of his first words. To Max, though, the syllable 'juice' was not just his academically correct identification of a external referent with certain properties, but it also served as a proposition: 'Give me some juice! Only at a later age did Max add more syllables, like 'gimme juice', to distinguish propositions from pure words. Vervets show no evidence of having reached that stage.

On the second question of extent of 'vocabulary', even the most advanced animals seem, on the basis of present knowledge, to be far behind us. The average human has a daily working vocabulary of around a thousand words; my compact desk dictionary claims to contain 142,000 words; but only ten calls have been distinguished even for vervets, the most intensively studied mammal. Animals and humans surely do differ in vocabulary size, yet the difference may not be as great as these numbers suggest. Remember how slow has been our progress in distinguishing vervet calls. Not until 1967 did anyone realize that these common animals had any calls with distinct meanings. The most experienced observers of vervets still cannot separate some of their calls without machine analysis, and even with machine analysis the distinctness of some of the suspected ten calls remain unproven. Obviously, vervets (and other animals) could have many other calls whose distinctness we have not yet recognized. There is nothing surprising about our difficulties in distinguishing animal sounds, when one considers our difficulties in distinguishing human sounds. Children devote much of their time for the first several years of their lives to learning how to recognize and reproduce the distinctions in the utterances of adults around them. As adults, we continue to have difficulty distinguishing sounds in unfamiliar human languages. After four years of high-school French between the ages of twelve and sixteen, my problems with understanding spoken French are embarrassing compared to the abilities of any four-year-old French child. But French is easy compared to the lyau language of New Guinea's Lakes Plains, in which a single vowel may have eight different meanings depending on its pitch. A slight change in pitch converts the meaning of the lyau word meaning 'mother-in-law' into 'snake'. Naturally, it would be suicidal for an lyau man to address his mother-in-law as 'beloved snake', and lyau children learn infallibly to hear and reproduce pitch distinctions that for years confounded even a professional linguist devoted full-time to the study of the lyau language. Given the problems we have ourselves with unfamiliar human languages, of course we must still be overlooking distinctions within the vervet vocabulary.

However, it is unlikely that any studies on vervets will reveal to us the limits attained by animal vocal communication, because those limits are probably reached by apes rather than by monkeys. While the sounds made by chimps and gorillas seem to our ears to be unsophisticated grunts and shrieks, so did the sounds made by vervet monkeys until they were studied carefully. Even unfamiliar human languages can sound like undifferentiated gibberish to us. Unfortunately, vocal communication by wild chimps and other apes has never been studied by the methods applied to vervets, because of logistical problems. The width of a troop's territory is typically less than 2,000 feet for vervets but is several miles for chimps, making it far harder to carry out playback experiments with video cameras and hidden loudspeakers. These logistical problems cannot be overcome by studying groups of apes caught in the wild and held captive in conveniently-sized zoo cages, because the captives generally constitute an artificial community of individuals caught at different African locations and thrown together in a cage. As I will discuss later in this chapter, humans originally speaking different languages, when captured at different African locations and thrown together as slaves, converse in only the crudest shadow of human language, virtually without any grammar. Similarly, captive apes taken from the wild must be virtually useless for studying the degree of sophistication of a vocal community of wild apes. The problem will remain unsolved until someone works out how to do for wild chimps what Cheney and Seyfarth have done for wild vervets.

Several groups of scientists have nevertheless spent years training captive gorillas, common chimps, and pygmy chimps to understand and use artificial languages based on plastic chips of different sizes and colours, or on hand signs similar to those used by deaf people, or on consoles, like a gigantic typewriter with each key bearing a different symbol. The animals have been reported to learn the meanings of up to several hundred symbols, and a pygmy chimp has recently been reported to understand (but not to utter) a good deal of spoken English. At the least, these studies of trained apes reveal that they possess the intellectual capabilities for mastering large vocabularies, begging the obvious question of whether they have evolved such vocabularies in the wild.

It is suspicious that wild gorilla troops may be seen sitting together for a long time, grunting back and forth in seemingly undifferentiated gibberish, until suddenly all the gorillas get up at the same time and head off in the same direction. One wonders whether there really was a transaction concealed within that gibberish. Because the anatomy of apes' vocal tracts restricts their ability to produce the variety of vowels and consonants that we can, the vocabulary of wild apes is unlikely to be anywhere as large as our own. Nevertheless, I would be surprised if wild chimp and gorilla vocabularies did not eclipse those reported for vervets and comprise dozens of 'words', possibly including names for individual animals. In this exciting field where new knowledge is being rapidly acquired, we should keep an open mind on the exact size of the vocabulary gap between apes and humans.

The last unanswered question concerns whether animal vocal communication involves anything that could be considered grammar or syntax. Humans do not only have vocabularies of thousands of words with different meanings. We also combine those words and vary their forms in ways prescribed by grammatical rules that determine the meaning of the word combinations. Grammar thereby allows us to construct a potentially infinite number of sentences from a finite number of words. To appreciate this point, consider the different meaning of the following two sentences, composed of the same words and endings but with different word order, which constitutes one set of the grammatical rules that specify sentence meaning in the English language:

'Your hungry dog bit my old mother's leg. or

'My hungry mother bit your old dog's leg.

If human language did not involve grammatical rules, those two sentences would have exactly the same meaning. Most linguists would not dignify an animal's system of vocal communication with the name of language, no matter how large its vocabulary, unless it also involved grammatical rules.

No hint of syntax has been discovered in the studies of vervets to date. Most of their grunts and alarm calls are single utterances. When a vervet gives a sequence of two or more utterances, all analysed cases have Jproved to consist of the same utterance repeated, as has also been the case when one vervet has been recorded responding to another vervet's call. Capuchin monkeys and gibbons do have calls of several elements used °nly in certain combinations or sequences, but the meanings of these combinations remain to be deciphered (by us humans, that is).

I doubt that any student of primate vocalizations expects even wild chimps to have evolved a grammar remotely approaching the complexity of human grammar, complete with prepositions, verb tenses, and interrogative particles. However, it remains for the present an open question whether any animal has evolved syntax. The necessary studies on the wild animals most likely to use grammar—pygmy or common chimps—simply have not yet been attempted.

In short, while the gulf between animal and human vocal communication is surely large, scientists are rapidly gaining understanding of the causeway that evolved over that gulf from the animal side. Now let's trace the bridge from the human side. We have already discovered complex animal 'languages'; do any truly primitive human languages still exist?

To help us recognize what a primitive human language might sound like if there were any, let's remind ourselves of the ways in which normal human language differs from vervet vocalizations. One difference is that of grammar. Humans, but not vervets, possess grammar, meaning the variations in word order, prefixes, suffixes, and changes in word roots (such as 'they', 'them', 'their') that modulate the sense of the roots. A second difference is that vervet vocalizations, if they constitute words at all, stand only for things that one can point to or act out. One could try to argue that vervet calls do include the equivalents of nouns ('eagle') and verbs or verb phrases ('watch out for the eagle'). Our words clearly include both nouns and verbs that are distinct from each other, as well as adjectives. Those three parts of a speech referring to specific objects, acts, or qualities are termed lexical items. But up to half of the words in typical human speech are purely grammatical items, with no referent that one can point to.

These grammatical words include our prepositions, conjunctions, articles, and auxiliary verbs (words like 'can', 'may', 'do', and 'should'). It is much harder to understand how grammatical items could evolve than it is for lexical items. Given someone who understands no English, you can point to your nose to explain what that noun means. Apes might similarly come to agree on the meanings of grunts functioning as nouns, verbs, or adjectives. How, though, do you explain the meaning of'by', 'because', 'the', and 'did' to someone who understands no English? How could apes have stumbled on such grammatical terms?

Yet another difference between human and vervet vocalizations is that ours possess a hierarchial structure, such that a modest number of items at each level creates a larger number of items at the next higher level. Our language uses many different syllables, all based on the same set of a few dozen sounds. We assemble those syllables into thousands of words. Those words are not merely strung haphazardly together but are organized into phrases, such as prepositional phrases. Those phrases in turn interlock to form a potentially infinite number of sentences. In contrast, vervet calls cannot be resolved into modular elements and lack even a single stage of hierarchical organization.

As children, we master all of this complex structure of human language without ever learning the explicit rules governing it. We are not forced to formulate the rules unless we study our own language in school or learn a foreign language from books. So complex is our language's structure that many of the underlying rules currently postulated by professional linguists have been proposed only in recent decades. This gulf between human language and animal vocalizations explains why most linguists never discuss how human language might have evolved from animal precursors. They instead regard that question as unanswerable and therefore unworthy even of speculation.

The earliest written languages of 5,000 years ago were as complex as those of today. Human language must have achieved its modern complexity long before that. Can we at least recognize linguistic missing links by searching for primitive peoples with simple languages that might represent early stages of language evolution? After all, some tribes of hunter-gatherers retain stone tools as simple as those that characterized the whole world tens of thousands of years ago. Nineteenth-century travel books abound with tales of backward tribes who supposedly used only a few hundred words or who lacked articulated sounds, were reduced to saying 'ugh', and depended on gestures for their communications. That was Darwin's first impression of the speech of the Indians in Tierra del Fuego. But all such tales proved to be pure myth. Darwin and other western travellers merely found it as hard to distinguish the unfamiliar sounds of non-western languages as non-westerners found English sounds, or as zoologists find the sounds of vervet monkeys. Actually, it turns out that there is no correlation between linguistic and social complexity. Technologically primitive people do not speak primitive languages, as I discovered on my first day among the Fore people in the New Guinea highlands. Fore grammar proved deliciously complex, with postpositions similar to those of the Finnish language, dual as well as singular and plural forms similar to those of Slovenian, and ^Verb tenses and phrase construction unlike any language I had encountered previously. I have already mentioned the eight vowel tones of New Guinea's lyau people, whose sound distinctions proved impercept-toly subtle to professional linguists for years. Nor could we reverse Darwin's prejudice by claiming an inverse correlation between linguistic and social complexity, citing the advanced civilizations of China and England, whose languages are simple in the sense of having little or no word inflection (verb conjugations and noun declensions). French verbs are much more highly inflected than are modern English verbs (nous aimons, vous aimez, Us aiment, etc.), yet the French consider themselves the most highly civilized people. Thus, while some peoples in the modern world retained primitive tools, none retained primitive languages. Furthermore, Cro-Magnon archaeological sites contain lots of preserved tools but no preserved words. The absence of such linguistic missing links deprives us of what might have been our best evidence about human language origins. We are forced to try more indirect approaches.

One indirect approach is to ask whether some people, deprived of the opportunity to hear any of our fully evolved, modern languages, ever spontaneously invented a primitive language. According to the Greek historian Herodotus, the Egyptian king Psammeticus intentionally carried out such an experiment in the hope of identifying the world's oldest language. The king assigned two newborn infants to a solitary shepherd to rear in strict silence, with instructions to listen for their first words. The shepherd duly reported that both children, after mouthing nothing but meaningless babble until the age of two, ran up to him and began constantly repeating the word becos. Since that word meant 'bread' in the Phrygian language then spoken in central Turkey, Psammeticus supposedly conceded that the Phrygians were the most ancient people. Unfortunately, Herodotus's brief account of Psammeticus's experiment fails to convince sceptics that it was carried out as rigorously as described. It illustrates why some scholars prefer to honour Herodotus as the Father of Lies, rather than as the Father of History. Certainly, solitary infants reared in social isolation, like the famous wolf boy of Aveyron, remain virtually speechless and do not invent or discover a language. However, a variant of the Psammeticus experiment has occurred dozens of times in the modern world. In this variant, whole populations of children heard adults around them speaking a grossly simplified and variable form of language, somewhat similar to that which normal children themselves speak at around the age of two years. The children proceeded unconsciously to evolve their own language, far advanced over vervet communication but simpler than normal human languages. The results were the new languages known as pidgins and Creoles, which may provide us with models of two missing links in the evolution of normal human language. My first experience of a Creole was with the New Guinea lingua franca known either as Neo-Melanesian or pidgin English. (The latter name is a confusing misnomer, since Neo-Melanesian is not a pidgin but rather a creole derived from an advanced pidgin -1 shall explain the difference later—and it is only one of many independently evolved languages equally misnamed as pidgin English.) Papua New Guinea boasts about 700 native languages within an area similar to that of Sweden, but no single one of those languages is spoken by more than three per cent of the population. Not surprisingly, a lingua franca was needed and it arose after the arrival of English-speaking traders and sailors in the early 1800s. Today, Neo-Melanesian serves in Papua New Guinea as the language not only of much conversation, but also of many schools, newspapers, radios, and parliamentary discussions. The advertisement in the appendix to this chapter (see pages 150-51) gives a sense of this newly evolved language.

When I arrived in Papua New Guinea and first heard Neo-Melanesian, I was scornful of it. It sounded like long-winded, grammarless baby-talk. On speaking a form of English according to my own notion of baby-talk, I was disturbed to discover that New Guineans did not understand me. My assumption that Neo-Melanesian words meant the same as their English cognates led to spectacular disasters, notably when I tried to apologize to a woman in her husband's presence for accidentally jostling her, only to find that Neo-Melanesian pushim does not mean 'push' but instead means 'have sexual intercourse with'.

Neo-Melanesian proved to be as strict as English in its grammatical rules. It was a subtle language that let one express anything sayable in English. It even let one make some distinctions that cannot be expressed in English except by means of clumsy circumlocutions. For example, the English pronoun 'we' actually lumps together two quite different concepts: 'I, plus you to whom I am speaking', and 'I, plus one or more other people, but not including you to whom I am speaking'. In Neo-Melanesian these two separate meanings are expressed by the words yumi and mipela respectively. After I have been using Neo-Melanesian for a few months and then meet an English-speaker who starts talking about we', I often find myself wondering, 'am I included or not in your "we"? Neo-Melanesian's deceptive simplicity and actual suppleness stem partly from its vocabulary, partly from its grammar. Its vocabulary is based on a modest number of core words whose meaning varies with context and becomes extended metaphorically. For instance, while Neo-Melanesiangras can mean English 'grass' (whencegras bilong solwara [salt water] means 'seaweed'), it also can mean 'hair' (whence man i no gat gras long head bilong em becomes 'bald man').

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for colonists and workers who speak differing native (first) languages and need to communicate with each other. Each group (colonists or workers) retains its native language for use within its own group; each group uses the pidgin to communicate with the other group, and in addition workers on a polyglot plantation may use pidgin to communicate with other groups of workers. An illustration of how quickly pidgins may arise is given by my own experience soon after I first arrived in Indonesia. An Indonesian worker and I were dropped together by helicopter in an uninhabited mountain range to survey birds. We had no Indonesian/ English dictionary, knew nothing of each other's language, and could teach each other words only by pointing. Within a week we had evolved a crude pidgin, based solely on Indonesian nouns, to communicate about camp chores: for instance rice fire meant 'to cook rice', while bird binoculars meant 'to watch birds'.

Compared to normal languages, pidgins are greatly impoverished in their sounds, vocabulary, and syntax. A pidgin's sounds are generally only those common to the two or more native languages thrown together. For example, many New Guineans find it hard to pronounce our consonants/ and v, but I and other native English speakers find it hard to pronounce the vowel tones and nasalized sounds rampant in many New Guinean languages. Such sounds became largely excluded from New Guinean pidgins and then from the Neo-Melanesian Creole that developed from them. Words of early-stage pidgins consist largely of nouns, verbs, and adjectives, with few or no articles, auxiliary verbs, conjunctions, prepositions, or pronouns. As for grammar, early-stage pidgin discourse typically consists of short strings of words with little phrase construction, no regularity in word order, no subordinate clauses, and no inflectional endings on words. Together with that impoverishment, variability of speech within and between individuals is a hallmark of early-stage pidgins, which approximate an anarchic linguistic free-for-all.

Pidgins that are used only casually by adults who otherwise retain their own separate native languages persist at this rudimentary level. For example, a pidgin known as Russonorsk grew up to facilitate barter between Russian and Norwegian fishermen who encountered each other in the Arctic. That lingua franca persisted throughout the Nineteenth Century but never developed further, as it was used only to transact simple business during brief visits. Both those groups of fishermen spent most of their time speaking Russian or Norwegian with their compatriots. In New Guinea, on the other hand, the pidgin gradually became more regular and complex over many generations because it was used intensively on a daily basis, but most children of New Guinean workers continued to learn their parents' native languages as their first language until after the Second World War.

However, pidgins evolve rapidly into Creoles when a generation of one of the groups contributing to a pidgin begins to adopt the pidgin itself as its native language. That generation then finds itself using pidgin for all social purposes, not only for discussing plantation tasks or bartering. Compared to pidgins, Creoles have a larger vocabulary, much more complex grammar, and consistency within and between individuals. Creoles can express virtually any thought expressible in a normal language, whereas trying to say anything even slightly complex is a desperate struggle in pidgin. Somehow, without any equivalent of the Academic Francaise to lay down explicit rules, a pidgin expands and stabilizes to become a uniform and more sophisticated language. This process of creolization is a natural experiment in language evolution that has unfolded independently dozens of times in the modern world. The sites for the experiment have ranged from mainland South America and Africa to Pacific islands; the labourers, from Africans and Portuguese to Chinese and New Guineans; the dominant colonists, from English and Spaniards to other Africans and Portuguese; and the century, from at least the Seventeenth to the Twentieth. What is striking is that the linguistic outcomes of all these independent natural experiments share so many similarities, both in what they lack and in what they possess. On the negative side, Creoles are simpler than normal languages in that they usually lack conjugations of verbs for tense and person, declensions of nouns for case and number, most prepositions, distinctions between events in the past and present, and agreement of words for gender. On the positive side, Creoles are advanced over pidgins in many respects: consistent word order; singular and plural pronouns for the first, second, and third persons; relative clauses; indications of the anterior tense (describing actions occurring before the time under discussion, whether or not that time is the present); and particles or auxiliary verbs preceding the main verb and indicating negation, anterior tense, conditional mood, and continuing as opposed to completed actions. Furthermore, most Creoles agree in placing a sentence's subject, verb, and object in that particular order, and also agree in the order of particles or auxiliaries preceding the main verb.

The factors responsible for this remarkable convergence are still controversial among linguists. It is as if you drew a dozen cards fifty times from well-shuffled decks and almost always ended up with no hearts or diamonds, but with one king, a jack, and two aces. The interpretation I hnd most convincing is that of linguist Derek Bickerton, who views many of the similarities among Creoles as a result of a human genetic blueprint for language.

Bickerton derived his view from his studies of creolization in Hawaii, where sugar planters imported workers from China, the Philippines, Japan, Korea, Portugal, and Puerto Rico in the late Nineteenth Century. Out of that linguistic chaos, and following Hawaii's annexation by the US in 1898, a pidgin based on English developed into a fully fledged Creole. The immigrant workers themselves retained their original native language. They also learned the pidgin that they heard, but they did not improve on it, despite its gross deficiencies as a medium of communication. That, however, posed a big problem for the immigrants' Hawaiian-born children. Even if the children were lucky enough to hear a normal language at home because both mother and father were from the same ethnic group, that normal language was useless for communicating with children and adults from other ethnic groups. Many children were less fortunate and heard nothing but pidgin even at home, when mother and father came from different ethnic groups. The children also did not have adequate opportunities to learn English because of the social barriers isolating them and their worker parents from the English-speaking plantation owners. Presented with an inconsistent and impoverished model of human language in the form of pidgin, Hawaiian labourers' children spontaneously 'expanded' pidgin into a consistent and complex Creole within a generation.

In the mid-1970s Bickerton was still able to trace the history of this creolization by interviewing working-class people born in Hawaii between 1900 and 1920. Like all of us, those children soaked up language skills in their early years but then became fixed in their ways, so that their speech in their old age continued to reflect the language spoken around them in their youth. (My children too will soon be wondering why their father persists in saying 'icebox' rather than 'refrigerator', decades after the iceboxes of my parents' own childhood disappeared.) Hence the elderly adults of various ages, whom Bickerton interviewed in the 1970s, provided him with virtually frozen snapshots of various stages in Hawaii's pidgin-to-creole transition, depending on the subjects' year of birth. In that way, Bickerton was able to conclude that creolization had begun by 1900, was complete by 1920, and was accomplished by children in the process of acquiring the ability to speak.

In effect, the Hawaiian children lived out a modified version of the Psammeticus experiment. Unlike the Psammeticus children, the Hawaiian children did hear adults speaking and were able to learn words. Unlike normal children, however, the Hawaiian children heard little grammar, and what they did hear was inconsistent and rudimentary. Instead, they created their own grammar. That they did indeed create it, rather than somehow borrowing grammar from the language of Chinese labourers or English plantation owners, is clear from the many features of Hawaiian Creole that differ from English or from the workers' languages. The same is true for Neo-Melanesian: its vocabulary is largely English, but its grammar includes many features absent from English.

I do not want to exaggerate the grammatical similarities among Creoles by implying that they are all essentially the same. Creoles do vary depending on the social history surrounding creolization—especially on the initial ratio between the numbers of plantation owners (or colonists) and workers, how quickly and to what extent that ratio changed, and for how many generations the early-stage pidgin could gradually borrow more complexity from existing languages. Yet many similarities remain, particularly among those Creoles that quickly arose from early-stage pidgins. How did each Creole's children come so quickly to agree on a grammar, and why did the children of different Creoles tend to reinvent the same grammatical features again and again? It was not because they did it in the easiest or sole way possible to devise a language. For instance, Creoles use prepositions (short words preceding nouns), as do English and some other languages, but there are other languages that dispense with prepositions in favour of postpositions following nouns, or else noun case endings. Again, Creoles happen to resemble English in placing subject, verb, and object in that order, but the borrowing from English could not account for Creole grammar, because Creoles derived from languages with a different word order still use the subject-verb-object order.

These similarities among Creoles seem likely to stem from a genetic blueprint that the human brain possesses for learning language during childhood. Such a blueprint has been widely assumed ever since the linguist Noam Chomsky argued that the structure of human language is far too complex for a child to learn within just a few years, in the absence of any hard-wired instructions. For example, at the age of two my twin sons were just beginning to use single words. As I write this paragraph a bare twenty months later, still several months short of their fourth birthday, they have already mastered most of the rules of basic English grammar that people who immigrate to English-speaking countries as adults often fail to master after decades. Even before the age of two, my children had learned to make sense of the initially incomprehensible babble of adult sound coming at them, to recognize groupings of syllables into words, and to realize which groupings constituted underlying words despite variations of pronunciation within and between adult speakers.

Such difficulties convinced Chomsky that children learning their first language would face an impossible task unless much of language's structure were already pre-programmed into them. Hence Chomsky reasoned that we are born with a 'universal grammar' already wired into °ur brains to give us a spectrum of grammatical models encompassing the range of grammars in actual languages. This pre-wired universal grammar would be like a set of switches, each with various alternative positions. The switch positions would then become fixed to match the grammar of the local language that the growing child hears. However, Bickerton goes further than Chomsky and concludes that we are pre-programmed not just to a universal grammar with adjustable switches, but to a particular set of switch settings: the settings that surface again and again in Creole grammars. The pre-programmed settings can be overridden if they turn out to conflict with what a child hears in the local language around it. But if a child hears no local switch settings at all because it grows up amidst the structureless anarchy of pidgin language, the Creole settings can persist.

If Bickerton is correct in that we really are pre-programmed at birth with Creole settings that can be overridden by later experience, then one would expect children to learn creole-like features of their local language earlier and more easily than features conflicting with Creole grammar. This reasoning might explain the notorious difficulty of English-speaking children in learning how to express negatives: they insist on creole-like double negatives such as 'Nobody don't have this'. The same reasoning could explain the difficulties of English-speaking children with word order in questions.

To pursue the latter example, English happens to be among the languages that uses the Creole word order of subject, verb, and object for statements: for instance, 'I want juice'. Many languages, including Creoles, preserve this word order in questions, which are merely distinguished by altered tone of voice ('You want juice? ). However, the English language does not treat questions in this way. Instead, our questions deviate from Creole word order by inverting the subject and verb ('Where are you? , not 'Where you are? ), or by placing the subject between an auxiliary verb (such as 'do') and the main verb ('Do you want juice? ). My wife and I have been barraging my sons from early infancy onwards with grammatically correct English questions as well as statements. My sons quickly picked up the correct order for statements, but both of them are still persisting in the incorrect creole-like order for questions, despite the hundreds of correct examples that my wife and I utter for them every day. Today's samples from Max and Joshua include 'Where it is? , 'What that letter is? , 'What the handle can do? , and 'What you did with it? . It is as if they are not yet ready to accept the evidence of their ears, because they are still convinced that their pre-programmed creole-like rules are correct.

I have discussed Creoles as if they appeared only with the rise of colonialism in the past 500 years. In fact, the social conditions that produced modern Creoles have arisen repeatedly during thousands of years of documented human history, and probably long before that. Hence some of the world's 'normal' languages may have passed through stages of creolization and gradually re-evolved a more complex grammar. The possible example closest to home is the language of these pages. There has been a long controversy among linguists over the history of the Germanic language family that includes English, and that presumably arose in the area of the Baltic Sea. As I shall discuss in Chapter Fifteen, Germanic languages belong to a wider grouping of languages termed Indo-European. All Indo-European languages clearly derived much of their vocabulary and grammar from an ancestral language known as proto-Indo-European, which may have been spoken in southern Russia 5,000 years ago and then spread west across Europe. However, the Germanic languages also include many word roots and grammatical features unique to them, and absent from all other Indo-European families. Familiar examples include the English words 'house', 'wife', and 'hand', close to the modern German words Haus, Weib, and Hand. The shores of the Baltic are the source of prized amber that was traded to southern Europe and Russia thousands of years ago, just as it is still traded around the world today. Could the Germanic languages have arisen as a Creole, when proto-Indo-European traders settled among proto-Germanic tribes of the Baltic to buy amber in exchange for pottery, battle-axes, and horses? Now let's pull together all these animal and human studies to try to form a coherent picture of how our ancestors progressed from grunts to Shakespeare's sonnets. A well-studied early stage is represented by vervet monkeys, with at least ten different calls that are under voluntary control, are used for communication, and have external referents. The calls may function as words, explanations, propositions, or as all of those things simultaneously. Scientists' difficulties in identifying those ten calls have been such that more surely await identification, but we still do not know how large the vervet vocabulary really is. We also do not know how far other animals may have progressed beyond vervets, because the vocal communications of the species most likely to have eclipsed vervets, the common and the pygmy chimp, have yet to be studied carefully in the wild. At least in the laboratory, chimps can master hundreds of symbols that we teach them, suggesting that they have the necessary intellectual equipment to master symbols of their own. The single words of young toddlers, like 'juice' as uttered by my son Max, constitute a next stage beyond animal grunts. Like vervet calls, Max's 'juice' may have functioned as some combination of a word, an explanation, and a proposition. But Max has made a decisive advance on vervets by assembling his 'juice' word from the smaller units of vowels and consonants, thereby scaling the lowest level of modular linguistic organization. A few dozen such phonetic units can be reshuffled to produce a very large number of words, such as the 142,000 words in my English desk dictionary. That principle of modular organization lets us recognize far more distinctions than can vervets. For example, they name only six types of animals, whereas we name nearly two million.

A further step towards Shakespeare is exemplified by two-year-old children, who in all human societies proceed spontaneously from a one-word to a two-word stage and then to a multi-word one. But those multi-word utterances are still mere word strings with little grammar, and their words are still nouns, verbs, and adjectives with concrete referents. As Bickerton points out, those word strings are rather like the pidgin languages that human adults spontaneously reinvent when necessary. They also resemble the strings of symbols produced by captive apes whom we have instructed in the use of those symbols.

From pidgins to Creoles, or from the word strings of two-year-olds to the complete sentences of four-year-olds, is another giant step. In that step were added words lacking external referents and serving purely grammatical functions; elements of grammar such as word order, prefixes and suffixes, and word root variation; and more levels of hierarchical organization to produce phrases and sentences. Perhaps that step is what triggered the Great Leap Forward discussed in Chapter Two. Nevertheless, Creole languages reinvented in modern times still give us clues to how these advances arose, through the Creoles' circumlocutions to express prepositions and other grammatical elements. As another illustration of how this might have happened, my Indonesian colleague and I were just in the process of reinventing prepositions when the helicopter picked us up and terminated our experiment in pidgin evolution. We had begun to assemble word strings that functioned as locative prepositional phrases but were still composed solely of nouns with concrete referents—strings such as 'spoon top plate' and 'spoon bottom plate', to mean that the spoon was on or under the plate. Many virtual prepositions in Neo-Melanesian, Indonesian, and other Creoles are similarly constructed.

If you compare the Neo-Melanesian advertisement on pages 150-51 with a Shakespearean sonnet, you might conclude that a huge gap still exists. In fact, I would argue that, with an advertisement like Katn insait long stua bilong mipela, we have come 99.9 % of the way from vervet calls to Shakespeare. Creoles already constitute expressive complex languages. For example, Indonesian, which arose as a Creole to become the language of conversation and government for the world's fifth most populous country, is also a vehicle for serious literature.

Animal communication and human language once seemed to be separated by an unbridgeable gulf. Now, we have identified not only parts of the bridges starting from both shores, but also a series of islands and bridge segments spaced across the gulf. We are beginning to understand in broad outline how the most unique and important attribute that distinguishes us from animals arose from animal precursors.

Try to understand this Neo-Melanesian advertisement for a department store: Kam insait long stua bilong mipela—stua bilong salim olgeta samting—mipela i-ken helpim yu long kisim wanem samting yu laikim bikpela na liklik long gutpela prais. I-gat gutpela kain kago long baiim na i-gat stap long helpim yu na lukautim yu long taim yu kam insait long dispela stua.

If some of the words look strangely familiar but do not quite make sense, read the advertisement aloud to yourself, concentrate on the sounds, and ignore the strange spelling. As the next step, here is the same advertisement rewritten with English spelling: Come inside long store belong me-fellow—store belong sellim altogether something—me-fellow can helpim you long catchim what-name something you likim, big-fellow na liklik, long good-fellow price. He-got good-fellow kind cargo long buyim, na he-got staff long helpim you na lookoutim you long time you come inside long this-fellow store.

A few explanations should help you make sense of the remaining strangenesses. Almost all the words in this sample of Neo-Melanesian are derived from English, except for the word liklik for 'little', derived from a New Guinean language (Tolai). Neo-Melanesian has only two pure prepositions: bilong, meaning 'of or 'in order to', and long, meaning almost any other English preposition. The English consonant/becomes p in Neo-Melanesian, as in stap for 'staff, andpe/a for 'fellow'. The suffix -pela is added to monosyllabic adjectives (hencegutpela for 'good', bikpela for 'big'), and also makes the singular pronouns 'me' and 'you' into plural ones (for 'we' and 'you'—plural). Na means 'and'. So the advertisement means:

Come into our store—a store for selling everything—we can help you get whatever you want, big and small, at a good price. There are good types of goods for sale, and staff to help you and look after you when you visit the store.

NINE ANIMAL ORIGINS OF ART

Art is often viewed as lacking animal precursors, cultivated solely for pleasure, and serving no biological function. In fact, even art experts have been unable to distinguish human artworks from those produced by apes and elephants. Like the bower decorations of bowerbirds, human art may have evolved as a signal of status and thereby helped us to pass on our genes. Georgia O'Keeffe's drawings were slow to win recognition for her, but Siri's drawings brought her acclaim as soon as other knowledgeable artists saw them. 'They had a kind of flair and decisiveness and originality'—that was the first reaction of the famous abstract-expressionist painter Willem de Kooning. Jerome Witkin, an authority on abstract expressionism who teaches art at Syracuse University, was even more effusive: 'These drawings are very lyrical, very, very beautiful. They are so positive and affirmative and tense, the energy is so compact and controlled, it's just incredible. . This drawing is so graceful, so delicate. . This drawing indicates a grasp of the essential mark that makes the emotion.

Witkin applauded Siri's balance of positive and negative space, and her placement and orientation of images. Having seen the drawings but knowing nothing about who made them, he guessed correctly that the artist was female and interested in Asian calligraphy. But Witkin did not guess that Siri was 8 feet tall and weighed 4 tons. She was an Asian elephant who drew by holding a pencil in her trunk. de Kooning's response to being told Siri's identity was, 'That's a damned talented elephant. Actually, Siri was not extraordinary by elephant standards. Wild elephants often use their trunks to make drawing motions in the dust, while captive elephants often spontaneously scratch marks on the ground with a stick or stone. Hanging in many doctors' and lawyers' offices are paintings by an elephant named Carol, who sold dozens of her works at prices of up to 500 dollars. Supposedly, art is the noblest distinctively human attribute—one that sets us apart from animals at least as sharply as does spoken language, by differing in basic ways from anything that any animal does. Art ranks as even nobler than language, since language is really 'just' a highly sophisticated advance on animal communication systems, serves an obvious biological function in helping us to survive, and obviously developed from the sounds made by other primates. In contrast, art serves no such transparent function, and its origins are considered a sublime mystery. But it is clear that elephant art could have implications for our own. At the minimum, it is a similar physical activity resulting in products that even experts could not distinguish from human products accepted as constituting art. Of course, there are also huge differences between Siri's art and ours, not least of which is that Siri was not trying to communicate her message to other elephants. Nevertheless, we cannot just dismiss her art as a quirk of one individual beast.

In this chapter I shall go beyond elephants to examine art-like activities of some other animals. I believe that the comparisons will help us understand the original functions of human art. Thus, although we usually consider art to be the antithesis of science, there may really be a science of art.

To appreciate that our art must have some animal precursors, recall from Chapter One that it is only about seven million years since we branched off from our closest living relatives, the chimpanzees. Seven million years sound like a lot on the scale of a human lifetime, but they are barely one per cent of the history of complex life on Earth. We still share over ninety-eight per cent of our genes with chimps. Art and those other features that we consider uniquely human must be due to just a tiny fraction of our genes. They must have arisen only a few moments ago on the evolutionary time clock.

Modern studies of animal behaviour have been shrinking the list of features once considered uniquely human, so much so that most differences between us and so-called animals now appear to be only matters of degree. For example, I described in Chapter Eight how vervet monkeys have a rudimentary language. You may not have considered vampire bats allied with us in nobility, but they prove to practise ^reciprocal altruism regularly (towards other vampire bats, of course). ^m°ⁿg our darker qualities, murder has now been documented in innumerable animal species, genocide in wolves and chimps, rape in ^Ucks and orangutans, and organized warfare and slave raids in ants.

As absolute distinctions between us and animals, these discoveries leave us few characteristics besides art, which we managed to dispense with for the first 6,960,000 of the seven million years since we diverged from chimps. Perhaps the earliest art forms were wood carving and body painting, but we would not know because they are not preserved. The first preserved, even questionable, hints of human art consist of some flower remains around Neanderthal skeletons, and some scratches on animal bones at Neanderthal campsites. However, their interpretation as having been arranged or scratched intentionally is in doubt. Not until the Cro-Magnons, beginning around 40,000 years ago, do we have unequivocal evidence for art surviving in the form of the famous cave paintings, statues, necklaces, and musical instruments. If we are going to claim that true art is unique to humans, then in what ways do we claim that it differs from superficially similar productions of animals, like bird-songs? Three supposed distinctions are often put forward: that human art is non-utilitarian, that it is only for aesthetic pleasure, and that it is transmitted by learning rather than through our genes. Let's scrutinize these claims more closely.

Firstly, as Oscar Wilde said, 'All art is quite useless. The implicit meaning a biologist sees behind this quip is that art is non-utilitarian in a narrow sense employed within the fields of animal behaviour and evolutionary biology. That is, human art does not help us to survive or to pass on our genes, which are the readily discernible functions of most animal behaviour. Of course, most human art is utilitarian in the broader sense that the artist thereby communicates something to fellow humans, but transmitting one's thoughts to the next generation is not the same thing as transmitting one's genes. In contrast, bird-song serves the obvious functions of wooing a mate, defending a territory, and thereby transmitting genes.

Regarding the second claim that human art is instead motivated by aesthetic pleasure, Webster's dictionary defines art as 'the making or doing of things that have form or beauty'. While we cannot ask mockingbirds and nightingales if they similarly enjoy the form or beauty of their songs, it is suspicious that they sing mainly during the breeding season. Hence they are probably not singing just for aesthetic pleasure. As for human art's third claimed distinction, each human group has a distinctive art style, and the knowledge of how to make and enjoy that particular style is learned, not inherited. For example, it is easy to distinguish typical songs being sung today in Tokyo and in Paris. But those stylistic differences are not hard-wired in our genes, as are the differences, say, in the eyes of Parisians and Japanese. Parisians and Japanese can and often do visit each other's cities and learn each other's songs. In contrast, many species of birds (the so-called nonpasserine birds) inherit the knowledge of how to produce and respond to the particular song of their species. Each of those birds would produce the right song even if it had never heard it, and even if it had heard only the songs of other species. It is as if a French baby adopted by Japanese parents, flown in infancy to Tokyo, and educated there began spontaneously to sing the 'Marseillaise'.

At this point, we may seem to be light-years removed from elephant art. Elephants are not even closely related to us evolutionarily. Much more relevant to us are the artworks that were produced by two captive chimpan/ees named Congo and Betsy, a gorilla called Sophie, an orangutan named Alexander, and a monkey named Pablo. These primates variously mastered the media of brush or finger-painting and pencil, chalk, or crayon drawing. Congo did up to thirty-three paintings in one day, apparently for his own satisfaction, as he did not show his work to other chimps and threw a tantrum when his pencil was taken away. For human artists, the ultimate proof of success is a one-man show, but Congo and Betsy were honoured by a two-chimp show of their paintings in 1957 at London's Institute of Contemporary Art. The following year, Congo had a one-chimp show at London's Royal Festival Hall. What is more, almost all of the paintings on exhibit at those chimp shows sold (to human buyers); plenty of human artists cannot make that boast. Still other ape paintings were surreptitiously entered into exhibits by human artists and were enthusiastically acclaimed by unsuspecting art critics for their dynamism, rhythm, and sense of balance. Equally unsuspecting were child psychologists who were given paintings by chimps from the Baltimore Zoo and were asked to diagnose the painters' problems. The psychologists guessed that a painting by a three-year-old male chirnp was instead by an aggressive seven- or eight-year-old boy with paranoid tendencies. Two paintings by the same one-year-old female chimp were attributed to different ten-year-old girls, one painting indicating a belligerent girl of the schizoid type, the other a paranoid girl with strong father identification. It is a tribute to the psychologists' insight that they intuited the artist's sex correctly in each case; they were only wrong about the artist's species.

These paintings by our closest relatives do start to blur the distinction between human art and animal activities. Like human paintings, the ape paintings served no narrow utilitarian function of transmitting genes, and were instead just produced for satisfaction. One could object that the ape artists, like the elephant Siri, made their pictures just for their own satisfaction, while most human artists aim to communicate to other nans. The apes did not even keep their paintings to enjoy themselves simply discarded them. Yet that objection does not strike me as fatal, e the simplest human art (doodling) is also regularly discarded, and since one of the best pieces of art I own is a wood statue carved by a New Guinea villager who discarded it under his house after carving it. Even some human art that later became famous was created by artists for their private satisfaction: the composer Charles Ives published little of his music, and Franz Kafka not only did not publish his three great novels but even forbade his executor to do so. (Fortunately, the executor disobeyed, thereby forcing Kafka's novels to take on a communicative function posthumously.)

However, there is a more serious objection against claiming a parallel between ape art and human art. Ape painting is just an unnatural activity of captive animals. One might insist that, since it is not natural behaviour, it could not illuminate the animal origins of art. Let us therefore turn now to some undeniably natural and illuminating behaviour: bowerbirds' building of bowers, the most elaborate structures built and decorated by any animal species other than humans. If I had not already heard of bowers, I would have mistaken the first one I saw for something man-made, as did nineteenth-century explorers in New Guinea. I had set out that morning from a New Guinea village, with its circular-huts, neat rows of flowers, people wearing decorative beads, and little bows and arrows carried by children in imitation of their fathers' larger ones. Suddenly, in the jungle, I came across a beautifully woven, circular hut 8 feet in diameter and 4,feet high, with a doorway large enough for a child to enter and sit inside. In front of the hut was a lawn of green moss, clean of debris except for hundreds of natural objects of various colours that had obviously been placed there intentionally as decorations. They mainly consisted of flowers and fruits and leaves, but also some butterfly wings and fungi. Objects of similar colour were grouped together, such as red fruits next to a group of red leaves. The largest decorations were a tall pile of black fungi facing the door, with another pile of orange fungi a few yards further from the door. All blue objects were grouped inside the hut, red ones outside, and yellow, purple, black, and a few green ones in other locations.

That hut was not a child's playground. It had instead been built and decorated by an otherwise unimpressive jay-sized bird called a bower-bird, a member of a family of eighteen species confined to New Guinea and Australia. Bowers are erected by males for the sole purpose of seducing females, who then bear the sole responsibility for building the nest and rearing the young. Males are polygamous, try to mate with as many females as possible, and provide the female with nothing except sperm. Females, often in groups, cruise around the bowers and inspect all the ones in the vicinity before selecting one at which to mate. Human equivalents of such scenes are played out every night on Sunset Strip, a few miles from my home in Los Angeles. Female bowerbirds select their bedmate by the quality of his bower, its number of decorations, and its conformity to local rules, which vary among species and populations of bowerbirds. Some populations prefer blue decorations, others red or green or grey, while some replace the hut with one or two towers, or a two-walled avenue, or a four-walled box. There are populations that paint their bowers with crushed leaves or else with oils that they excrete. These local differences in rules appear not to be hard-wired into the birds' genes. Instead, they are learned through younger birds observing older birds during the many years that it takes a bowerbird to reach adulthood. Males learn the locally correct way to decorate, while females learn those same rules for the purpose of choosing a male.

I tested the males' finickiness by moving decorations, whereupon the bower owner restored them to their original places. When I put out poker chips of various colours, the hated white chips were heaved off into the jungle, the beloved blue ones stacked inside the hut, and the red ones stacked on the lawn next to red leaves and fruits.

At first, this system strikes us as absurd. After all, what a female bowerbird is trying to do is to pick a good mate. The evolutionary winner in such a mate-selection contest is that female bowerbird who picks that male bowerbird who makes it possible for her to leave the largest number of surviving offspring. What good does it do her to pick the guy with the blue fruits? All animals face similar problems of mate selection. I have already discussed our own problems and solutions in Chapter Five. Consider those species (such as most European and North American songbirds) whose males carve out mutually exclusive territories that each male will share with his mate. The territory contains the nest site and food resources for the female to use in rearing her young. Hence a part of the female's task is to assess the quality of each male's territory.

Alternatively, suppose that the male himself will assist in feeding and protecting the young, and in hunting cooperatively with the female. Then the female and the male must assess each other's parenting and hunting skills and the quality of their relationship. All these things are hard enough to assess, but it is even harder for the female to assess a male when he provides nothing but sperm and genes, as is the case with male bowerbirds. How on earth is an animal to assess a prospective mate's 8^£nes, and what have blue fruits to do with good genes?

Animals do not have the time to produce ten offspring with each of many prospective mates, and to compare the outcomes (the eventual number of surviving offspring). Instead, they have to resort to shortcuts by relying on mating signals such as songs or ritualized displays. As I shall discuss at more length in Chapter Eleven, it is now a hotly contested problem in animal behaviour to understand why, or even whether, those mating signals serve as veiled indicators of good genes. We have only to reflect on our own difficulties in selecting mates and in assessing the true wealth, parenting skills, and genetic quality of our various prospective partners.

In this light, reflect what it means when a female bowerbird finds a male with a good bower. She knows at once that that male is strong, since the bower he assembled weighs hundreds of times his own weight, and since he had to drag some individual decorations half his weight from dozens of yards distant. She knows that the male has the mechanical dexterity needed to weave hundreds of sticks into a hut, tower, or walls. He must have a good brain, to carry out the complex design correctly. He must have good vision and memory to search out the required hundreds of decorations in the jungle. He must be good at coping with life, to have survived to the age of perfecting all those skills. He must also be dominant over other males—since males spend much of their leisure time trying to wreck and steal from each other's bowers, only the best males end up with intact bowers and many decorations.

Thus, bower-building provides a comprehensive test of male genes. It is as if women put each of their suitors in sequence through a weight-lifting contest, sewing contest, chess tournament, eye test, and boxing tournament, and finally went to bed with the winner. By comparison with bowerbirds, our efforts to identify mates with good genes are pathetic. We grasp at external bagatelles like facial features and ear lobe lengths (Chapter Five), or like sex appeal and Porsche ownership, which tell nothing about intrinsic genetic worth. Think of all the human suffering caused by the sad truth that beautiful sexy women or handsome Porsche-owning men often prove to have miserable genes for other traits. It is.-no wonder that so many marriages end in divorce, as we belatedly realize how badly we chose and how flimsy our criteria were. How did bowerbirds evolve to use art so cleverly for such important purposes? Most male birds woo females by advertising their colourful bodies, songs, displays, or offerings of food, as dim indicators of good genes. Males of two groups of birds of paradise in New Guinea go one step further by clearing areas on the jungle floor, as bowerbirds do, to enhance their displays and show off their fancy plumage. Males of one of those birds of paradise have gone still further by decorating their cleared areas with objects useful to a nesting female: pieces of snakeskin to line her nest, pieces of chalk or mammal faeces to eat for their minerals, and fruits to eat for their calories. Finally, bowerbirds have learned that decorative objects useless in themselves may nevertheless be useful indicators of good genes, if the objects are ones that were difficult to acquire and keep.

We can easily relate to that concept. Just think of all those advertisements showing a handsome man presenting a diamond ring to a seemingly fertile young woman. You cannot eat a diamond ring, but a woman knows that the gift of such a ring tells far more about the resources that her suitor commands (and might devote to her offspring and herself) than a gift of a box of chocolates would tell. Yes, chocolates provide a few useful calories, but they are quickly gone and any idiot can afford to buy them. In contrast, the man who can afford that inedible diamond ring has money to support the woman and her kids, and also has whatever genes (for intelligence, persistence, energy, etc.) that it took to acquire or hold on to the money.

Comparisons of different bowerbird species and their bowers show that male bowerbirds achieve through bowers what other birds achieve through bright plumage. Bowerbird species differ in the conspicuousness of adult male plumage. For example, males of the five species that build towers or huts sport brilliant yellow-orange crests, whose lengths vary among the species from 4 inches to nothing at all. The shorter the crest, the bigger the bower, and the more numerous and diverse its decorations. It makes sense that a male whose manly ornament is reduced to a runty 2 inches should go to great lengths to compensate in other ways.

Thus, in the course of bowerbird evolution the less resplendent males have lured the female's attention from ornaments that are permanent parts of the male's body to ornaments that the male gathers. Whereas sexual selection in most species has produced differences between males and females in their bodily ornaments (Chapter Six), in bowerbirds it has shifted towards causing males to emphasize collected ornaments separate from their bodies. From this perspective, bowerbirds are rather human. We, too, rarely court (or at least rarely initiate courtship) by displaying the beauties of our unadorned naked bodies. Instead, we swathe ourselves in coloured cloths, spray or daub ourselves with perfumes and paints and powders, and augment our beauty with decorations ranging from jewels to sports cars. The parallel between bowerbirds and humans may be even closer if, as friends of mine who are into sports cars assure me, duller young men tend to decorate themselves with fancier sports cars.

Now let's re-examine, in the light of bowerbirds, those three criteria supposedly separating human art from any animal production. Both bower styles and our art styles are learned rather than inherited, so that there is no difference by the third criterion. As for the second criterion (doing it for aesthetic pleasure), it is unanswerable. We cannot ask bowerbirds whether they get pleasure out of their art, and I suspect that many humans who claim to do so arejust putting on cultural affectations. That leaves only the first criterion: Oscar Wilde's assertion that art is useless, in a narrow biological sense. His statement is definitely untrue of bower art, which serves a sexual function. But it is absurd to pretend any longer that our own art lacks biological functions. Instead, there are several ways in which art helps us to survive and to pass on our genes.

Firstly, art often brings direct sexual benefits to its owner. It is not just a joke that men bent on seduction invite a woman to view their etchings. In real life, dance and music and poetry are common preludes to sex.

Secondly, and much more importantly, art brings indirect benefits to its owner. Art is a quick indicator of status, which—in human as in animal societies—is a key to acquiring food, land, and sexual partners. Yes, bowerbirds get the credit for discovering the principle that ornaments separate from one's body are more flexible status symbols than ornaments that one has to grow, but we still get credit for running away with that principle. Cro-Magnons decorated their bodies with bracelets, pendants, and ochre; New Guinea villagers today decorate theirs with shells, fur, and bird-of-paradise plumes. In addition to these art forms for bodily adornment, both Cro-Magnons and New Guinea villagers produced larger art (carvings and paintings) of world quality. We know that New Guinea art signals superiority and wealth, because birds of paradise are hard to hunt, beautiful statues take talent to make, and both are very expensive to buy. These badges of distinction are essential for marital sex in New Guinea: brides are bought, and part of the price consists of luxury art. Elsewhere as well, art is often viewed as a signal of talent, money, or both. In a world where art is a coin of sex, it is only a small further step for some artists to be able to convert art into food. There are whole societies that support themselves by making art for trade to food-producing groups. For example, the Siassi islanders, who lived on tiny islets with little room for gardens, survived by carving beautiful bowls that other tribes coveted for bride payments and paid for in food.

The same principles hold even more strongly in the modern world. Where we once signalled our status with bird feathers on our bodies and a giant clam shell in our hut, we now do it with diamonds on our bodies and a Picasso on our wall. Where Siassi islanders sold a carved bowl for the equivalent of twenty dollars, Richard Strauss built himself a villa with the proceeds from his opera Salome and earned a fortune from Der Rosenkavalier. Nowadays we read increasingly often of art sold at auction for tens of millions of dollars, and of art theft. In short, precisely because it serves as a signal of good genes and ample resources, art can be cashed in for still more genes and resources. So far, I have considered only the benefits that art brings to individuals, but art also helps define human groups. Humans have always formed competing groups whose survival is essential if the individuals in that group are to pass on their genes. Human history largely consists of the details of groups killing, enslaving, or expelling other groups. The winner takes the loser's land, sometimes also the loser's women, and thus the loser's opportunity to perpetuate genes. Group cohesion depends on the group's distinctive culture—especially its language, religion, and art (including stories and dances), hence art is a significant force behind group survival. Even if you have better genes than most of your fellow tribesmen, it will do you no good should your whole tribe (including you) get annihilated by some other tribe.

By now, you're probably protesting that I have gone completely overboard in ascribing utility to art. What about all of us who just enjoy art, without converting it to status or sex? What about all the artists who remain celibate? Are there not easier ways to seduce a sex partner than to take piano lessons for ten years? Is private satisfaction not a (the?) main reason for our art, just as for Siri and Congo?

Of course. Such expansion of behavioural patterns far beyond their original role is typical of animal species whose foraging efficiency gives them much leisure time, and who have brought their survival problems under control. Bowerbirds and birds of paradise have much leisure time, because they are big and feed on wild fruit trees out of which they can kick smaller birds. We have much leisure time because we use tools to obtain food. Animals with leisure time can channel it into more lavish signals to outdo each other. Those types of behaviour may then come to serve other purposes, such as representing information (a suggested function of Cro-Magnon cave paintings of hunted animals), relieving boredom (a real problem for captive apes and elephants), channelling neurotic energy (a problem for us as well as for them), and just providing pleasure. To maintain that art is useful is not to deny that art provides pleasure. Indeed, if we were not programmed to enjoy art, it could not serve most of its useful functions for us. Perhaps we can now answer the question why art as we know it characterizes us, but no other animal. Since chimps paint in captivity, why do they not do so in the wild? As a solution, I suggest that wild chimps still have their day filled with problems of finding food, surviving, and fending off rival chimp groups. If wild chimps had more leisure time plus the means to manufacture paints, they would be painting. The proof of my theory is that it actually happened: we are still ninety-eight per cent chimps in our genes.

Thus, human art has come far beyond its original functions. But let us not forget that even the greatest art may still serve those primal functions. As evidence, may I quote excerpts from a letter that an English lady named Rebecca Schroter wrote to the famous musician who was her lover:

This letter of surrender was addressed to the composer Franz Josef Haydn, who, at the same time as he was enjoying this doting English lover, also boasted of an Italian mistress and an Austrian wife. Haydn knew how to use great art for its original purposes.

TEN AGRICULTURE'S TWO-EDGED SWORD

Agriculture is conventionally regarded as the human hallmark whose adoption made the biggest material contribution to the improvement in our lifestyle over that of apes. In fact, recent archaeological studies have made it clear that agriculture brought many of the curses as well as the blessings of modern civilization.

To science, we owe dramatic changes in our smug self-image. Astronomy taught us that our Earth is not the centre of the universe but merely one of nine planets circling one of billions of stars. From biology, we learned that humans were not specially created by God but evolved along with tens of millions of other species. Now, archaeology is demolishing another sacred belief: that human history over the last million years has been a long tale of progress. In particular, recent discoveries suggest that the adoption of agriculture (plus animal husbandry), supposedly our most decisive step towards a better life, was actually a milestone for the worse as well as for the better. With agriculture came not only greatly increased food production and food storage, but also the gross social and sexual inequality, the disease and despotism, that curse modern human existence. Thus, among the human cultural hallmarks being discussed in Part Three of this book, agriculture represents in its mixed blessings a halfway station between our noble traits discussed in Chapters Eight and Nine (art and language) and our unmitigated vices, discussed in many of the remaining chapters (drug abuse, genocide, and environmental destructiveness).

At first, the evidence for progress and against this revisionist interpretation will strike twentieth-century Americans and Europeans as irrefutable. We are better off in almost every respect than people of the Middle Ages, who in turn had it easier than Ice-Age cavemen, who were still better off than apes. If you are inclined to be cynical, just count our advantages. We enjoy the most abundant and varied food, the best tools and material goods, the longest and healthiest lives in human history. Most of us are safe from starvation and predators. We obtain most of our energy from oil and machines, not just from our sweat. What neo-Luddite among us would really trade the life of today for that of a medieval peasant, caveman, or ape? For most of our history, all humans had to practise a primitive lifestyle termed 'hunting and gathering': they hunted wild animals and gathered wild plant food. That hunter-gatherer lifestyle is often characterized by anthropologists as 'nasty, brutish, and short'. Since no food is grown and little is stored, there is (according to this view) no respite from the time-consuming struggle that starts anew each day to find wild foods and avoid starving. Our escape from this misery was launched only after the end of the last Ice Age, when people began independently in different parts of the world to domesticate plants and animals (see Chapter Fourteen). The agricultural revolution gradually spread until today it is nearly universal and few tribes of hunter-gatherers survive. From the progressivist perspective on which I was brought up, the question 'Why did almost all our hunter-gatherer ancestors adopt agriculture? is silly. Of course they adopted it because agriculture is an efficient way to get more food for less work. Our planted crops yield far more tons per acre than do wild roots and berries. Just imagine savage hunters, exhausted from searching for nuts and chasing wild animals, suddenly gazing for the first time at a fruit-laden orchard or a pasture full of sheep. How many milliseconds do you think it took those hunters to appreciate the advantages of agriculture?

The progressivist party line goes further and credits agriculture with giving rise to art, the noblest flowering of the human spirit. Since crops can be stored, and since it takes less time to grow food in gardens than to find it in the jungle, agriculture gave us free time that hunter-gatherers never had. But free time is essential for creating art and enjoying it. Ultimately it was agriculture that, as its greatest gift, enabled us to build the Parthenon and compose the B Minor Mass. Among our major cultural hallmarks, agriculture is especially recent, having begun to emerge only 10,000 years ago. None of our primate relatives practises anything remotely resembling agriculture. For the most similar animal precedents, we must turn to ants, which invented not only plant domestication but also animal domestication.

Plant domestication is practised by a group of several dozen related species of New World ants. All those ants cultivate specialized species of yeasts or fungi in gardens within the ants' nest. Rather then relying on natural soil, each gardener ant species gathers its own particular type of compost: some ants grow their crop on caterpillar faeces, others on insect corpses or dead plant material, and still others (the so-called leaf-cutter ants) on fresh leaves, stems, and flowers. For example, leaf-cutter ants clip off leaves, slice them into pieces, scrape off foreign fungi and bacteria, and take the pieces into underground nests. There the leaf fragments are crushed into moist pellets of a paste-like consistency, manured with ant saliva and faeces, and seeded with the ants' preferred species of fungus, which serves as the ants' main or sole food. In an operation the equivalent of weeding a garden, the ants continually remove any spores or threads of other fungus species that they may find growing on their leaf paste. When a queen ant goes off to found a new colony, she carries with her a starting culture of the precious fungus, just as human pioneers bring along seeds to plant.

As for animal domestication, ants obtain a concentrated sugary secretion termed honeydew from diverse insects, ranging from aphids, caterpillars, and mealybugs to scale insects, treehoppers, and spittle insects. In return for the honeydew, the ants protect their 'cows' from predators and parasites. Some aphids have evolved into virtually the insect equivalent of domestic cattle: they lack offensive structures of their own, excrete honeydew from their anus, and have a specialized anal anatomy designed to hold the droplet in place while an ant drinks it. To milk their cow and stimulate honeydew flow, ants stroke the aphid with their antennae. Some ants care for their aphids in the ants' nest during the cold winter, then in the spring carry the aphids at the correct stage of development to the correct part of the correct food plant. When aphids eventually develop wings and disperse in search of a new habitat, some lucky ones are discovered by ants and 'adopted'.

Obviously, we did not inherit plant and animal domestication directly from ants but reinvented it. Actually, 're-evolved' is a better term than 'reinvented', since our early steps towards agriculture did not consist of conscious experimentation towards an articulated goal. Instead, agriculture grew from human behaviours, and from responses or changes in plants and animals, leading unforeseen towards domestication. For example, animal domestication arose partly from people keeping captive wild animals as pets, partly from wild animals learning to profit from the proximity of people (such as wolves following human hunters to catch crippled prey). Similarly, early stages of plant domestication included people harvesting wild plants and discarding seeds, which were thereby accidentally 'planted'. The inevitable result was unconscious selection of those plant and animal species and individuals most useful to humans. Eventually, conscious selection and care followed.

Now let's return to the progressivist view of this agricultural revolution of ours. As I explained at the outset of this chapter, we are accustomed to assuming that the transition from the hunter-gatherer lifestyle to agriculture brought us health, longevity, security, leisure, and great art. While the case for this view seems overwhelming, it is hard to prove. How do you actually show that lives of people 10,000 years ago got better when they abandoned hunting for farming? Until recently, archaeologists could not test this question directly. Instead, they had to resort to indirect tests, whose results (surprisingly) failed to support the view of agriculture as an unmixed blessing. Here is one example of such an indirect test. If agriculture had been visibly such a great idea, you would expect it to have spread quickly, once it arose in some source area. In fact, the archaeqlogical record shows that agriculture advanced across Europe at literally a snail's pace: barely 1,000 yards per year! From its origins in the Near East around 8000 BC, agriculture crept north-westwards to reach Greece around 6000 BC and Britain and Scandinavia only 2,500 years later. That is hardly what you can call a wave of enthusiasm. As recently as the Nineteenth Century, all the Indians of California, now the fruit-basket of America, remained hunter-gatherers, even though they knew of agriculture through trade with farming Indians in Arizona. Were California Indians really blind to their self-interest? Or, could it instead be that they were smart enough to see, hidden beyond agriculture's glittering facade, the drawbacks that ensnared the rest of us?

Another indirect test of the progressivist view is to study whether surviving twentieth-century hunter-gatherers really are worse off than farmers. Scattered throughout the world, mainly in areas unsuitable for agriculture, several dozen groups of so-called 'primitive people', like the Kalahari Desert Bushmen, continued to live as hunter-gatherers in recent years. Astonishingly, it turns out that these hunters generally have leisure time, sleep a lot, and work no harder than their farming neighbours. For instance, the average time devoted each week to obtaining food has been reported to be only twelve to nineteen hours for Bushmen; how many readers of this book can boast of such a short working week? As one Bushman replied when asked why he had not emulated neighbouring tribes by adopting agriculture, 'Why should we plant, when there are so many mongongo nuts in the world?

Of course, one's belly is not filled only by finding food; the food also has to be processed for eating, and that can take a lot of time for things like mongongo nuts. It would be a mistake to swing to the opposite extreme from the progressivist view and to regard hunter-gatherers as living a life of leisure, as some anthropologists have done. However, it would also be a mistake to view them as working much harder than farmers. Compared to my physician and lawyer friends today, and to my shopkeeper grandparents in the early Twentieth Century, hunter-gatherers really do have more free time.

While farmers concentrate on high-carbohydrate crops like rice and potatoes, the mixture of wild plants and animals in the diets of surviving hunters provides more protein and a better balance of other nutrients. The Bushmen's average daily food intake is 2,140 calories and 93 grams of protein, considerably greater than the US RDA (Recommended Daily Allowance) for people of their small size but vigorous activity. Hunters are healthy, suffer from little disease, enjoy a very diverse diet, and do not experience the periodic famines that befall farmers dependent on few crops. It is almost inconceivable for Bushmen, who utilize eighty-five edible wild plants, to die of starvation, as did about a million Irish farmers and their families during the 1840s when a blight attacked potatoes, their staple crop.

Thus, the lives of at least the surviving modern hunter-gatherers are not 'nasty, brutish, and short', even though farmers have pushed them into the world's worst real-estate. Hunters of the past, who still occupied fertile lands, could hardly have been worse off than modern hunters. However, all those modern hunter societies have been affected by farming societies for thousands of years and do not tell us about the condition of hunters before the agricultural revolution. The progressivist view is really making a claim about the distant past: that the lives of people in each part of the world got better when they switched from hunting to farming. Archaeologists can date that switch by distinguishing remains of wild plants and animals from remains of domestic ones in prehistoric rubbish dumps. How can one deduce the health of the prehistoric rubbish makers, and thereby test directly for agriculture's supposed blessings?

That question has become answerable only in recent years, through the newly emerging science of'paleopathology': looking for signs of disease (the science of pathology) in remains of ancient peoples (from the Greek word paieo meaning 'ancient', as in paleontology). In some lucky situations, the paleopathologist has almost as much material to study as does a pathologist. For example, archaeologists in the deserts of Chile found well-preserved mummies whose medical condition at time of death could be determined by an autopsy, just as one would do on a fresh corpse in a hospital today. Faeces of long-dead Indians who lived in dry caves in Nevada remained sufficiently well-preserved to examine for hookworm and other parasites.

Usually, though, the only human remains available for paleo-pathologists to study are skeletons, but they still permit a surprising number of deductions about health. To begin with, a skeleton identifies its owner's sex, and his/her weight and approximate age at time of death. Thus, with enough skeletons, one can construct mortality tables like those used by life insurance companies to calculate expected lifespan and risk of death at any given age. Paleopathologists can also calculate growth rates by measuring bones of people of different ages, can examine teeth for cavities (signs of a high-carbohydrate diet) or enamel defects (signs of a poor diet in childhood), and can recognize scars that many diseases such as anaemia, tuberculosis, leprosy, and osteoarthritis leave on bones.

One straightforward example of what paleopathologists have learned from skeletons concerns historical changes in height. Many modern cases illustrate how improved childhood nutrition leads to taller adults: for instance, we stoop to pass through doorways of medieval castles built for a shorter, malnourished population. Paleopathologists studying ancient skeletons from Greece and Turkey found a striking parallel. The average height of hunter-gatherers in that region towards the end of the Ice Age was a generous 5 foot 10 inches for men, 5 foot 6 inches for women. With the adoption of agriculture, height crashed, reaching by 4000 BC a low value of only 5 foot 3 inches for men, 5 foot 1 inch for women. By classical times, heights were very slowly on the rise again, but modern Greeks and Turks have still not regained the heights of their healthy hunter-gatherer ancestors.

Another example of paleopathologists at work is the study of thousands of American Indian skeletons excavated from burial mounds in the Illinois and Ohio River valleys. Corn, first domesticated in Central America thousands of years ago, became the basis of intensive farming in those valleys around 1000 AD. Until then, Indian hunter-gatherers had skeletonsjso healthy it is somewhat discouraging to work with them', as one paleopathologist complained. With the arrival of corn, Indian skeletons suddenly became interesting to study. The number of cavities in an average adult's mouth jumped from less than one to nearly seven, and tooth loss and abscesses became rampant. Enamel defects in children's milk teeth imply that pregnant and nursing mothers were severely undernourished. Anaemia quadrupled in frequency; tuberculosis became established as an epidemic disease; half the population suffered from yaws or syphilis; and two-thirds suffered from osteoarthritis and other degenerative diseases. Mortality rates at every age increased, with the result that only one per cent of the population survived past the age of fifty, as compared to five per cent in the golden days before corn. Almost one-fifth of the whole population died between the ages of one and four, probably because weaned toddlers succumbed to malnutrition and infectious diseases. Thus, corn, usually considered among the New World's blessings, actually proved to be a public health disaster. Similar conclusions about the transition from hunting to farming emerge from studies of skeletons elsewhere in the world.

There are at least three sets of reasons to explain these findings that agriculture was bad for health. Firstly, hunter-gatherers enjoyed a varied diet with adequate amounts of protein, vitamins, and minerals, while farmers obtained most of their food from starchy crops. In effect, the farmers gained cheap calories at the cost of poor nutrition. Today just three high-carbohydrate plants—wheat, rice, and corn—provide more than fifty per cent of the calories consumed by the human species.

Secondly, because of that dependence on one or a few crops, farmers ran a greater risk of starvation if one food crop failed than did hunters. The Irish potato famine is merely one of many examples.

Finally, most of today's leading infectious diseases and parasites of mankind could not become established until after the transition to agriculture. These killers persist only in societies of crowded, malnourished, sedentary people constantly reinfected by each other and by their own sewage. The cholera bacterium, for example, does not survive for long outside the human body. It spreads from one victim to the next through contamination of drinking water with faeces of cholera patients. Measles dies out in small populations once it has either killed or immunized most potential hosts; only in populations numbering at least a few hundred thousand people can it maintain itself indefinitely. Such crowd epidemics could not persist in small, scattered bands of hunters who often shifted camp. Tuberculosis, leprosy, and cholera had to await the rise of farming, while smallpox, bubonic plague, and measles appeared only in the past few thousand years with the rise of cities.

Besides malnutrition, starvation, and epidemic diseases, farming brought another curse to humanity—class divisions. Hunter-gatherers have little or no stored food, and no concentrated food sources such as an orchard or herd of cows. Instead, they live off the wild plants and animals that they obtain each day. Everybody except for infants, the sick, and the old joins in the search for food. Thus, there can be no kings, no full-time professionals, no class of social parasites who grow fat on food seized from others.

Only in a farming population could contrasts between the disease ridden masses and a healthy, non-producing, elite develop. Skeletons from Greek tombs at Mycenae around 1500 BC suggest that royals enjoyed a better diet than commoners, since the royal skeletons were two or three inches taller and had better teeth (on the average, one instead of six cavities or missing teeth). Among mummies from Chilean cemeteries around 1000 AD, the elite were distinguished not only by ornaments and gold hairclips, but also by a four-fold lower rate of bone lesions stemming from infectious diseases.

These signs, of health differentials within local communities of farmers in the past appear on a global scale in the modern world. To most American and European readers, the argument that humanity could on the average be better off as hunter-gatherers than we are today sounds ridiculous, because most people in industrial societies today enjoy better health than most hunter-gatherers. However, Americans and Europeans are an elite in today's world, dependent on oil and other materials imported from countries with large peasant populations and much lower health standards. If you could choose between being a middle-class American, a Bushman hunter, and a peasant farmer in Ethiopia, the first choice would undoubtedly be the healthiest one, but the third choice might be the least healthy.

While giving rise to class divisions for the first time, farming may also have exacerbated sexual inequality already in existence. With the advent of agriculture, women often became beasts of burden, were drained by more frequent pregnancies (see below), and thus suffered poorer health. For example, among the 'Chilean mummies from 1000 AD, women exceeded men in osteoarthritis and in bone lesions from infectious diseases. In New Guinea farming communities today I often see women staggering under a load of vegetables and firewood while the men walk empty-handed. In one case I offered to pay some villagers to carry supplies from an airstrip to my mountain camp, and a group of men, women, and children volunteered. The heaviest item was a 110-pound bag of rice, which I lashed to a pole and assigned to a team of four men to shoulder the pole together. When I eventually caught up with the villagers, the men were carrying light loads, while one small woman weighing less than the bag of rice was bent under it, supporting its weight by a cord across her temples.

As for the claim that agriculture laid the foundations of art by providing us with leisure time, modern hunter-gatherers have on the average at least as much free time as do farmers. I grant that some people in industrial and farming societies enjoy more leisure than hunter-gatherers, at the expense of many others who support them and have far less leisure. Farming undoubtedly made it possible to sustain full-time craftsmen and artists, without whom we would not have such large-scale art projects as the Sistine Chapel and Cologne Cathedral. However, the whole emphasis on leisure time as a critical factor in explaining artistic differences among human societies seems to me misguided. It is not lack of time that prevents us today from surpassing the beauty of the Parthenon. While post-agricultural technological advances did make new art forms possible and art preservation easier, great paintings and sculptures on a smaller scale than that of Cologne Cathedral were already being produced by Cro-Magnon hunter-gatherers 15,000 years ago. Great art was still being produced in modern times by hunter-gatherers such as Eskimos and Pacific Northwest Indians. In addition, when we count up the specialists whom society became able to support after the advent of agriculture, we should recall not only Michelangelo and Shakespeare but also standing armies of professional killers.

Thus, with the advent of agriculture an elite became healthier, but many people became worse off. Instead of the progressivist party line that we chose agriculture because it was good for us, a cynic might ask how we got trapped by agriculture despite its being such a mixed blessing. The answer boils down to the adage, 'Might makes right. Farming could support far more people than hunting, whether or not it also brought on the average more food per mouth. (Population densities of hunter-gatherers are typically one person or less per square mile, while densities of farmers average at least ten times higher.) Partly, this is because an acre of field planted entirely in edible crops produces far more tons of food, and allows one to feed far more mouths, than an acre of forest with scattered edible wild plants. Partly, too, it is because nomadic hunter-gatherers have to keep their children spaced at four-year intervals by infanticide and other means, since a mother must carry her toddler until it is old enough to keep up with the adults. Because sedentary farmers do not have that problem, they can and do have a child every two years. Perhaps the main reason we find it so hard to shake off the traditional view that farming was unequivocally good for us is that there is no doubt that it meant more tons of food per acre. We forget that it also meant more mouths to feed, and that health and quality of life depend on the amount of food per mouth. As population densities of hunter-gatherers slowly rose at the end of the Ice Age, bands had to 'choose', whether consciously or unconsciously, between feeding more mouths by taking the first steps towards agriculture, or else finding ways to limit growth. Some bands adopted the former solution, unable to anticipate the evils of farming, and seduced by the transient abundance they enjoyed until population growth caught up with increased food production. Such bands outbred and then drove off or killed the bands that chose to remain hunter-gatherers, because ten malnourished farmers can still outfight one healthy hunter. It is not that hunter-gatherers abandoned their lifestyle, but that those sensible enough not to abandon it were forced out of all areas except ones that farmers did not want. Modern hunter-gatherers persisted only in scattered areas useless for agriculture, such as the Arctic, deserts, and some rainforests. At this point it is ironic to recall the common complaint that archaeology is an expensive luxury, concerned with the remote past, and offering no lessons of present relevance. Archaeologists studying the rise of farming have reconstructed for us a stage where we made one of the most crucial decisions in human history. Forced to choose between limiting population growth or trying to increase food production, we opted for the latter and ended up with starvation, warfare, and tyranny. The same choice faces us today, with the difference that we now can learn from the past.

Hunter-gatherers practised the most successful and long-persistent lifestyle in the career of our species. In contrast, we are still struggling with the problems into which we descended with agriculture, and it is unclear whether we can solve them. Suppose that an archaeologist who had visited us from outer space were trying to explain human history to his fellow spacelings. The visitor might illustrate the results of his digs by a twenty-four-hour clock on which one hour of clock-time represents 100,000 years of real past time. If the history of the human race began at midnight, then we would now be almost at the end of our first day. We lived as hunter-gatherers for nearly the whole of that day, from midnight through dawn, noon, and sunset. Finally, at 11:54 pm we adopted agriculture. In retrospect, the decision was inevitable, and there is now no question of turning back. But as our second midnight approaches, will the present plight of African peasants gradually spread to engulf all of us? Or, will we somehow achieve those seductive blessings that we imagine behind agriculture's glittering facade, and that have so far eluded us except in mixed form?

ELEVEN WHY DO WE SMOKE, DRINK, AND USE DANGEROUS DRUGS?

Self-destructive chemical abuse by humans has precedents in animal displays that are costly or dangerous to the displaying animal. Such behaviour may have originated from the dilemma that signals available to any individual lend themselves to cheating. But costly or dangerous signals carry a built-in guarantee of honesty and are thus useful—as long as their benefits outweigh their costs. Unfortunately, this old evolutionary framework has gone awry in us.

Chernobyl—formaldehyde in drywalls—asbestos—lead poisoning—smog—the Valdez oil spill—Love Canal—Agent Orange… Hardly a month goes by without our learning of yet another way in which we and our children have been exposed to toxic chemicals through the negligence of others. The public's outrage, sense of helplessness, and demand for change are growing. Why, then, do we do to ourselves that which we cannot stand for others to do to us? How do we explain the paradox that many people intentionally consume, inject, or inhale toxic chemicals, such as alcohol, cocaine, and the chemicals in tobacco smoke? Why are various forms of this wilful self-damage native to many contemporary societies, from primitive tribes to high-tech urbanites, and extending back into the past as far as we have written records?

Like the subjects of the preceding three chapters, drug abuse is also a hallmark virtually unique to the human species, albeit an evil one rather than a noble one (like language and art) or a mixed blessing (agriculture). «is not the worst of our evil hallmarks; it does not threaten the survival of civilization, as do our genocidal tendencies and our environmental destructiveness. But it is still damaging and widespread enough to beg the question of its origins.

The problem is not so much in understanding why we continue to take toxic chemicals once we have started. In part, that is because our drugs of abuse are addictive. Instead, the greater mystery is what impels us to begin at all. Evidence for the damaging or lethal effects of alcohol, cocaine, and tobacco is by now overwhelming and familiar. Only the existence of some strong countervailing motives could explain why people consume these poisons voluntarily, even eagerly. It is as if unconscious programmes were driving us to do something we know to be dangerous. What could those programmes be?

Naturally, there is no single explanation: different motives carry different weight with different people or in different societies. For instance, some people drink to overcome their inhibitions, others to deaden their feelings or drown their sorrows, still others because they like the taste of alcoholic beverages. Naturally, too, differences among human populations and social classes in their options for achieving satisfying lives largely account for geographic and class differences in chemical abuse. It is not surprising that self-destructive alcoholism is a bigger problem in high-unemployment areas of Ireland than in Southeast England, or that cocaine and heroin addiction is commoner in Harlem than in affluent suburbs. Hence it is tempting to dismiss drug abuse as a human hallmark with obvious social and cultural causes, and in no need of a search for animal precedents.

However, none of the motives that I have just mentioned goes to the heart of the paradox of our actively seeking what we know to be harmful. In this chapter I shall propose one other contributing motive which does address that paradox. It relates our chemical self-assaults to a wide range of seemingly self-destructive traits in animals, and to a general theory of animal signalling. It unifies a wide range of phenomena in our culture, from smoking and alcoholism to drug abuse. It has potential cross-cultural validity, for it may explain not just phenomena of the Western world but also some otherwise mystifying customs elsewhere, such as kerosene drinking by Indonesian kung-fu experts. I will also reach into the past and apply the theory to the seemingly bizarre practice of ceremonial enemas in ancient Mayan civilization.

Let me begin by relating how I arrived at this idea. One day, I was abruptly struck by the puzzle that companies manufacturing toxic chemicals for human use advertise their use explicitly. This business practice would seem a sure route to bankruptcy. Yet, while we do not tolerate advertisements for cocaine, advertisements for tobacco and alcohol are so widespread that we cease to regard their existence as puzzling. It hit me only after I had been living with New Guinea hunters in the jungle for many months, far from any advertising.

Day after day, my New Guinea friends had been asking me about Western customs, and I had come to realize through their astonished responses how senseless many of our customs are. Then the months of fieldwork ended with one of those sudden transitions that modern transportation has made possible. On 25 June I was still in the jungle, watching a brilliantly coloured male bird of paradise flap awkwardly across a clearing, dragging its 3-foot-long tail behind it. On 26 June I was sitting in a Boeing 747 jet, reading the magazines and catching up on the wonders of Western civilization.

I leafed through the first magazine. It fell open to a page with a photograph of a tough-looking man on horseback chasing cows, and the name of a brand of cigarette in large letters below. The American in me knew what the photograph was about, but part of me was still in the jungle, looking at that photo naively. Perhaps my reaction will not seem so strange to you if you try to imagine yourself completely unfamiliar with Western society, seeing the advertisement for the first time, and trying to fathom the connection between chasing cows and smoking (or not smoking) cigarettes.

The naive part of me, fresh out of the jungle, thought: such a brilliant anti-smoking ad! It is well known that smoking impairs athletic ability and causes cancer and early death. Cowboys are widely regarded as athletic and admirable. This advertisement must be a devastating new appeal by the anti-smoking forces, telling us that if we smoke that particular brand of cigarette, we will not be fit to be cowboys. What an effective message to our youth!

But then it became obvious that the advertisement had been put there by the cigarette company itself, which somehow hoped that readers would draw exactly the opposite message from the advertisement. How on earth did the company let its public relations department talk it into such a disastrous miscalculation? Surely, that advertisement would dissuade any person concerned about his/her strength and self-image from starting to smoke. Still half immersed in the jungle, I turned to another page. There I saw a photo of a whisky bottle on a table, a man sipping presumably the bottle's contents from a glass, and an obviously fertile young woman gazing at him admiringly as if she were on the verge of sexual surrender. How can that be, I asked myself? Everyone knows that alcohol interferes with sexual function, tends to make men impotent, makes one likely to stumble, impairs judgement, and predisposes to cirrhosis of the liver and other debilitating conditions. In the immortal words of the porter in Shakespeare's Macbeth, 'It [drink] provokes the desire, but it takes away the performance. A man with such handicaps should conceal them at all costs from a woman he aims to seduce. Why is the man in the photograph intentionally displaying those handicaps? Do whisky manufacturers think that pictures of this impaired individual will help sell their product? One could expect that Mothers Against Drunk Driving would be the ones producing such advertisements, and that the whisky companies would be suing to prevent publication.

Page after page of advertisements flaunted the use of cigarettes or strong alcohol, and hinted at their benefits. There were even pictures of young people smoking in the presence of attractive members of the opposite sex, as if to imply that smoking too brought sexual opportunities. Yet any non-smoker who has ever been kissed by (or tried to kiss) a smoker knows how severely the smoker's bad breath compromises his or her sex appeal. The advertisement paradoxically implied not just sexual benefits but also platonic friendships, business opportunities, vigour, health, and happiness, when the direct conclusion to be drawn from the advertisements was actually the reverse.

As the days passed and I reimmersed myself in Western civilization, I gradually stopped noticing its apparently self-defeating advertisements. I retreated into analysing my field data and wondering instead about an entirely different paradox, involving bird evolution. That paradox was what led me finally to understand one rationale behind cigarette and whisky advertisements. The new paradox concerned the reason that male bird of paradise I had been watching on 25 June had evolved the impediment of a tail 3 feet long. Males of other bird of paradise species evolved other bizarre impediments, such as long plumes growing out of their eyebrows, the habit of hanging upside-down, and brilliant colours and loud calls likely to attract hawks. All those features must impair male survival, yet they also serve as the advertisements by which male birds of paradise woo female birds of paradise. Like many other biologists, I found myself wondering why male birds of paradise use such handicaps as advertisements, and why females find the handicaps attractive.

At that point I came across a remarkable paper by an Israeli biologist, Amotz Zahavi, who had conceived a novel general theory about the role of costly or self-destructive signals in animal behaviour. For example, Zahavi attempted to explain how deleterious male traits might attract a female precisely because they constitute handicaps. On reflection, I decided that Zahavi's hypothesis might apply to the birds of paradise I studied. Suddenly I realized, with growing excitement, that his theory perhaps could also be extended to explain the paradox of our use of toxic chemicals, and our touting it in advertisements.

Zahavi's theory as he proposed it concerned the broad problem of animal communication. All animals need to devise quick, easily understood signals for conveying messages to their mates, potential mates, offspring, parents, rivals, and would-be predators. For example, consider a gazelle that notices a lion stalking it. It would be in the gazelle's interests to give a signal that the lion would interpret to mean, 'I am a superior, fast gazelle! You'll never succeed in catching me, so don't waste your time and energy on trying. Even if that gazelle really is able to outrun a lion, giving a signal that dissuades the lion from trying would save time and energy for the gazelle too. But what signal will unequivocally tell the lion that it is hopeless? The gazelle cannot take the time to run a demonstration 100-yard dash in front of every lion that shows up. Perhaps gazelles could agree on some quick arbitrary signal that lions learn to understand, such as that pawing the ground with the left hind foot means 'I claim that I'm fast! However, such a purely arbitrary signal opens the door to cheating; any gazelle can easily give the signal regardless of its speed. Lions will then catch on that many slow gazelles giving the signal are lying, and lions will learn to ignore the signal. It is in the interests both of lions and of fast gazelles that the signal be believable. What type of signal could convince a lion of the gazelle's honesty? The same dilemma arises in the problem of sexual selection and mate choice that I discussed in Chapters Five, Six, and Nine. This is especially a problem of how females pick males, since females invest more in reproduction, have more to lose, and have to be choosier. Ideally, a female should pick a male for his good genes to pass on to her offspring. Since genes themselves are hard to assess, a female should look for quick indicators of good genes in a male, and a superior male should provide such indicators. In practice, male traits such as plumage, songs, and displays usually serve as indicators. Why do males 'choose' to advertise with those particular indicators, why should females trust a male's honesty and find those indicators attractive, and why do they imply good genes?

I have described the problem as if a gazelle or courting male voluntarily picks out some indicator from among many possible ones, and as if a lion or a female decides on reflection whether it is really a valid indicator of speed or good genes. In practice, of course, those 'choices' are the result °f evolution and become specified by genes. Those females who select males on the basis of indicators that really denote good male genes, and those males that use unambiguous indicators of good genes for self-advertisement, tend to leave the most offspring, as do those gazelles and lions that spare themselves unnecessary chases. As it turns out, many of the advertising signals evolved by animals pose a paradox similar to that posed by cigarette advertisements. The indicators often seem to be ones that do not suggest speed or good genes but instead constitute handicaps, expenses, or sources of risk. For example, a gazelle's signal to a lion that it sees approaching consists of a peculiar form of behaviour termed 'slotting'. Instead of running away as fast as possible, the gazelle runs slowly while repeatedly jumping high into the air with stiff-legged leaps. Why on earth should the gazelle indulge in this seemingly self-destructive display, which wastes time and energy and gives the lion a chance to catch up? Or think of the males of many animal species which sport large structures, such as a peacock's tail or a bird of paradise's plumes, that make movement difficult. Males of many more species have bright colours, loud songs, or conspicuous displays that attract predators. Why should a male advertise such an impediment, and why should a female like it? These paradoxes remain an important unsolved problem in animal behaviour today.

Zahavi's theory, which remains controversial among biologists, goes to the heart of this paradox. According to his theory, those deleterious structures and forms of behaviour constitute valid indicators that the signalling animal is being honest in its claim of superiority, precisely because those traits themselves impose handicaps. A signal that entails no cost lends itself to cheating, since even a slow or inferior animal can afford to give the signal. Only costly or deleterious signals are guarantees of honesty. For example, a slow gazelle that slotted at an approaching lion would seal its fate, whereas a fast gazelle could still outrun the lion after slotting. By slotting, the gazelle boasts lo the lion, 'I'm so fasl that I can escape you even after giving you this head slarl. The lion ihereby has grounds for believing in ihe gazelle's honesty, and both ihe lion and ihe gazelle profit by nol wasling lime and energy on a chase whose outcome is cerlain. Similarly, as applied lo males displaying towards females, Zahavi's iheory reasons lhal any male lhal has managed lo survive despite ihe handicap of a big lail or conspicuous song musl have terrific genes in other respects. He has proved thai he musl be especially good al escaping predalors, finding food, and resisling disease. The bigger ihe handicap, ihe more rigorous ihe lest lhal he has passed. The female who selects such a male is like the medieval damsel testing her knighl suilors by walching ihem slay dragons. When she sees a one-armed knighl who can slill slay a dragon, she knows lhal she has finally found a knighl wilh greal genes. Thai knighl, by flaunting his handicap, is aclually flaunting his superiority.

Il seems lo me lhal Zahavi's iheory applies to much cosily or dangerous human behaviour aimed at achieving stalus in general or al sexual benefils in particular. For inslance, men who woo women wilh cosily gifts and olher displays of weallh are in effecl saying, 'I have plenty of money lo support you and children, and you can believe my boast because you see how much money I'm spending now withoul blanching. People who show off expensive jewels, sports cars, or works of art gain slalus because ihe signal cannol be faked; everyone else knows whal those oslentatious objecls cosl. American Indians of ihe Pacific Norlh-wesl used lo seek slalus by competing lo give away as much weallh as possible in ceremonies known as pollalch riluals. In ihe days before modern medicine, lallooing was not only painful bul dangerous because of ihe risk of infection; hence lallooed people in effecl were advertising two facels of iheir slrenglh, resistance lo disease plus tolerance of pain. Men on ihe Pacific island of Malekula show off by the insanely dangerous practice of building a high tower and jumping off it head first, after lying one end of some sloul vines lo iheir ankles and ihe olher end lo ihe lop of the tower. The length of ihe vines is calculaled to slop ihe braggart's plunge while his head is still a few feel above ihe ground. Survival guaranlees lhal ihe jumper is courageous, carefully calculating, and a good builder. Zahavi's iheory can also be exlended lo human abuse of chemicals. Especially in adolescence and early adullhood, ihe age when drug abuse is mosl likely lo begin, we are devoting much energy to asserting our stalus. I suggesl lhal we share ihe same unconscious inslincl lhal leads birds lo indulge in dangerous displays. Ten ihousand years ago, we 'displayed' by challenging a lion or a Iribal enemy. Today, we do it in olher ways, such as by fast driving or by consuming dangerous drugs.

The messages of our old and new displays nevertheless remain ihe same: I'm strong and superior. Even lo lake drugs only once or Iwice, I musl be slrong enough lo gel pasl ihe burning, choking sensation of my firsl puff on a cigarette, or to gel pasl ihe misery of my firsl hangover. To do ii chronically and remain alive and heallhy, I musl be superior (so I imagine). Il is a message to our rivals, our peers, our prospective males—and lo ourselves. The smoker's kiss may lasle awful, and the drinker may be impotenl in bed, bul he or she slill hopes lo impress peers or allracl mates by the implicil message of superiorily.

Alas, ihe message may be valid for birds, bul for us il is a false one. Like so many animal instincts in us, this one has become maladaptive in modern human society. If you can still walk after drinking a bottle of whisky, it may prove thai you have high levels of liver alcohol dehydrogenase, bul il implies no superiority in olher respects. If you have not developed lung cancer after chronically smoking several packs of cigarettes daily, you may have a gene for resistance to lung cancer, but thai gene does nol convey intelligence, business acumen, or the ability to creale happiness for your spouse and children.

It is true that animals with only brief lives and courtships have no alternative except to develop quick indicators, since prospective mates don't have enough time to measure each other's real quality. But we, with our long lives and courtships and business associations, have ample time to scrutinize each other's worth. We need not rely on superficial, misleading indicators. Drug abuse is a classic instance of a once-useful instinct—the reliance on handicap signals—that has turned foul in us. It is that old instinct to which the tobacco and whisky companies are directing their clever, obscene advertisements. If we legalized cocaine, the drug lords too would soon have advertisements appealing to the same instinct. You can easily picture it: the photo of the cowboy on his horse, or the suave man and the attractive maiden, above the tastefully displayed packet of white powder.

Now, let's test my theory by jumping from Western Industrialized Society to the other side of the world. Drug abuse did not begin with the Industrial Revolution. Tobacco was a native American Indian crop, native alcoholic beverages are widespread in the world, and cocaine and opium came to us from other societies. The oldest preserved code of laws, that of the Babylonian king Hammurabi (1792-50 BC), already contained a section regulating drinking houses. Hence my theory, if it is valid, should apply to other societies as well. As an instance of its cross-cultural explanatory power, I shall cite a practice you may not have heard of- kung-fu kerosene drinking. I learned of this practice when I was working in Indonesia with a wonderful young biologist named Ardy Irwanto. Ardy and I had come to like and admire each other, and to look out for each other's well-being. At one point, when we reached a troubled area and I expressed concern about dangerous people we might encounter, Ardy assured me, 'No problem, Jared. I have kung-fu grade eight. He explained that he practised the Oriental martial art of kung-fu and had reached a high level of proficiency, such that he could single-handedly fight off a group of eight attackers. To illustrate, Ardy showed me a scar in his back stemming from an attack by eight ruffians. One had knifed him, whereupon Ardy broke the arms of two and the skull of a third and the remainder fled. I had nothing to fear in Ardy's company, he told me.

One evening at our campsite, Ardy walked with his drinking cup up to our jerrycans. As usual, we had two cans: a blue one for water, and a red one for kerosene for our pressure lamp. To my horror, I watched Ardy pour from the red jerry can and raise the cup to his lips. Remembering an awful moment during a mountaineering expedition when I had taken a sip of kerosene by mistake and spent all the next day coughing it back up, I screamed to Ardy to stop. But he raised his hand and said calmly, 'No problem, Jared. I have kung-fu grade eight.

Ardy explained that kung-fu gave him strength, which he and his fellow kung-fu masters tested each month by drinking a cup of kerosene. Without kung-fu, of course, kerosene would make a weaker person sick. Heaven forbid that I, Jared, for instance, should try it. But it did him, Ardy, no harm, because he had kung-fu. He calmly retired to his tent to sip his kerosene and emerged the next morning, happy and healthy as usual.

I cannot believe that kerosene did Ardy no harm. I wish that he could have found a less damaging way to make periodic tests of his preparedness. But for him and his kung-fu associates, it served as an indicator of their strength and their advanced level of kung-fu. Only a really robust person could get through that test. Kerosene drinking illustrates the handicap theory of toxic chemical use, in a form as startlingly repellent to us as our cigarettes and alcohol horrified Ardy. In my last example, I shall generalize my theory further by extending its application to the past—in this case, to the civilization of Mayan Indians that flourished in Central America one or two thousand years ago. Archaeologists have been fascinated by Mayan success at creating an advanced society in the middle of tropical rainforest. Many Mayan achievements, such as their calendar, writing, astronomical knowledge, and agricultural practices, are now understood to varying degrees. However, archaeologists were long puzzled by slender tubes of unknown purpose that they kept finding in Mayan excavations.

The tubes' function finally became clear with the discovery of painted vases showing scenes of the tubes' use: to administer intoxicating enemas. The vases depict a high-status figure, evidently a priest or a prince, receiving a ceremonial enema in the presence of other people. The enema tube is shown as connected to a bag of a frothy beer-like beverage—probably containing either alcohol or hallucinogens or both, as suggested by practices of other Indian groups. Many Central and South

American Indian tribes formerly practised similar ritual enemas when first encountered by European explorers, and some still do so today. The substances known to be administered range from alcohol (made by fermenting agave sap or a tree bark) to tobacco, peyote, LSD derivatives, and mushroom-derived hallucinogens. Thus, the ritual enema is similar to our consumption of intoxicants by mouth, but there are four reasons why an enema constitutes a more effective and valid indicator of strength than does drinking.

Firstly, it is possible to relapse into solitary drinking and thus to lose all opportunity for signalling one's high status to others. However, it is more difficult for a solitary person to administer the same beverage to himself or herself unassisted as an enema. An enema encourages one to enlist associates and thereby automatically creates an occasion for self-advertisement. Secondly, more strength is required to handle alcohol as an enema than as a drink, since the alcohol goes directly into the intestine and thence to the bloodstream, and it is not first diluted with food in the stomach. Thirdly, drugs absorbed from the small intestine after ingestion by mouth pass first to the liver, where many drugs are detoxified before they can reach the brain and other sensitive organs. But drugs absorbed from the rectum after an enema bypass the liver. Finally, nausea may limit one's intake of drinks but not of enemas. Hence an enema seems to me a more convincing advertisement of superiority than are our whisky advertisements. I recommend this concept to an ambitious public relations firm competing for the account of one of the large distilleries. Let's now step back and summarize the perspective on chemical abuse that I have suggested. Although frequent self-destruction by chemicals may be unique to humans, I see it as fitting into a broad pattern of animal behaviour and thus as having innumerable animal precedents. All animals have had to evolve signals for quickly communicating messages to other animals. If the signals were ones that any individual animal could master or acquire, they would lend themselves to rampant cheating and hence to disbelief. To be valid and believable, a signal must be one that guarantees the honesty of the signaller, by entailing a cost, risk, or burden that only superior individuals can afford. Many animal signals that would otherwise strike us as counterproductive—such as stotting by gazelles, or costly structures and risky displays with which males court females—can be understood in this light.

It seems to me that this perspective has contributed to the evolution not only of human art, already discussed in Chapter Nine, but also of human chemical abuse as discussed in this chapter. Both art and chemical abuse are widespread human hallmarks characteristic of most known human societies. Both beg explanation, since it is not immediately obvious why they promote our survival through natural selection, or why they help us acquire mates through sexual selection. I argued in Chapter Nine that art often serves as a valid indicator of an individual's superiority or status, since art requires skill to create and requires status or wealth to acquire. But those individuals perceived by their fellows as enjoying status thereby acquire enhanced access to resources and mates. I have argued in this chapter that humans seek status through many other costly displays besides art, and that some of those displays (like jumping from towers, fast driving, and chemical abuse) are surprisingly dangerous. The former costly displays advertise status or wealth; the latter, dangerous ones advertise that the displaying individual can master even such risks and hence must be superior. I do not claim, though, that this perspective affords a total understanding of art or chemical abuse. As I mentioned in Chapter Nine in connection with art, complex patterns of behaviour acquire a life of their own, go far beyond their original purpose (if there ever was just a single purpose), and may even originally have served multiple functions. Just as art is now motivated far more by pleasure than by need for advertisement, chemical abuse too is now clearly much more than an advertisement. It is also a way to get past inhibitions, drown sorrows, or just enjoy a good-tasting drink.

I also do not deny that, even from an evolutionary perspective, there remains a basic difference between human abuse of chemicals and its animal precedents. Stotting, long tails, and all the animal precedents that I described involve costs, but those forms of behaviour persist because the costs are outweighed by the benefits. A stotting gazelle loses a possible head start in a chase, but gains by decreasing the likelihood that a lion will embark on a serious chase at all. A long-tailed male bird is encumbered in finding food or escaping predators, but those survival disadvantages imposed by natural selection are more than compensated by mating advantages gained through sexual selection. The net balance is more rather than fewer offspring to pass on the male's genes. These animal traits only appear to be self-destructive; they are actually self-promoting. In the case of our chemical abuse, though, the costs outweigh the benefits. Drug addicts and drunkards not only lead shorter lives, but they lose rather than gain attractiveness in the eyes of potential mates and lose the ability to care for children. These traits do not persist because of hidden advantages outweighing costs; they persist mainly because they are chemically addicting. Thus, on balance, they are self-destructive, not self-promoting, patterns of behaviour. While gazelles may occasionally miscalculate in stotting, they do not commit suicide through addiction to the excitement of stotting. In that respect, our self-destructive abuse of chemicals diverged from its animal precursors to become truly a human hallmark.

TWELVE ALONE IN A CROWDED UNIVERSE

While humans are unique among Earth's species, the enormous number of stars suggests that intelligent creatures like us must have evolved elsewhere in the universe. If so, why have we not been visited by their flying saucers? The insights that woodpeckers provide into the supposed inevitability of convergent evolution help us reassess the possibility that we are unique in the accessible universe as well as on Earth.

The next time you are outdoors on a clear night away from city lights, look up at the sky and get a sense of the myriads of stars. Next, find a pair of binoculars, train them on the Milky Way, and appreciate how many more stars escaped your naked eye. Then look at a photo of the Andromeda Nebula as seen through a powerful telescope to realize how enormous is the number of stars that escaped your binoculars as well.

Once all those numbers have sunk in, you will finally be ready to ask how humans could possibly be unique in the universe. How many civilizations of intelligent beings like ourselves must be out there, looking back at us? How long before we are in communication with them, before we visit them, or before we are visited?

On Earth, we certainly are unique. No other species possesses language, art, or agriculture of a complexity remotely approaching ours. No other species abuses drugs. But we have seen in the last four chapters that, for each of those human hallmarks, there are many animal precedents or even precursors. Accept for the moment the assumption that the universe contains innumerable other planets on which life evolved. Do not those considerations suggest that some other species on some other planets have also extended such widespread precursors as far as the level of our own intelligence, technical ability, and communication skills? While no other species on Earth is now wondering where else in the universe there exists intelligent life, such species must exist elsewhere. Alas, most human hallmarks lack effects detectable at a distance of many light-years. If there were creatures enjoying art or addicted to drugs on planets orbiting even the nearest stars, we would never know it. But fortunately there are two signs of intelligent beings elsewhere that might be detectable on Earth—space probes and radio signals. We ourselves are already becoming effective at sending out both, so surely other intelligent creatures have mastered the necessary skills. Where, then, are the expected flying saucers? This seems to me one of the greatest puzzles in all of science. Given the billions of stars, and given the abilities that we know did develop in our own species, we ought to be detecting flying saucers or at least radio signals. There is no question about there being billions of stars. What is there about the human species, then, that could explain the missing saucers? Could we really be unique not only on Earth, but also in the accessible universe? In this chapter I shall argue that we can obtain a fresh perspective on our uniqueness by looking carefully at some other well-known creatures here on Earth—woodpeckers!

For a long time, people have asked themselves such questions. Already around 400 BC the philosopher Metrodorus wrote, 'To consider the Earth the only populated world in an infinite space is as absurd as to assert that in an entire field sown with millet, only one grain will grow. Not until 1960, however, did scientists make a serious first attempt to find the answer, by listening (unsuccessfully) for radio transmissions from two nearby stars. In 1974 astronomers at the giant Arecibo radio telescope tried to establish an interstellar dialogue, by beaming a powerful radio signal to the star cluster M13 in the constellation Hercules. The signal described to Hercules' denizens what we earthlings look like, how many of us there are, and where the Earth is located in our solar system. Two years later the search for extraterrestrial life provided the main motivation behind the Viking missions to Mars, whose cost of about a billion dollars dwarfed all the US National Science Foundation's expenditures (since its inception) for classifying the life known to exist on Earth. More recently the US government has decided to spend a further hundred million dollars to detect radio signals from any intelligent beings who might exist outside our solar system. Several spacecraft that we launched are now heading out of our solar system, carrying sound tapes and photographic records of our civilization to inform spacelings who might be encountered.

It is easy to understand why lay people as well as biologists would consider the detection of extraterrestrial life as possibly the most exciting scientific discovery ever made. Just imagine how it would affect our self-image to find that the universe holds other intelligent creatures, with complex societies, languages, and learned cultural traditions, and capable of communicating with us. Among those of us who believe in an afterlife and an ethically concerned deity, most would agree that an afterlife awaits humans but not beetles (or even chimpanzees). Creationists believe that our species had a separate origin through divine creation. Suppose, though, that we should detect on another planet a society of seven-legged creatures more intelligent and ethical than we are, and able to converse with us, but having a radio receiver and transmitter in place of eyes and a mouth. Shall we believe that those creatures (but still not chimps) share the afterlife with us, and that they too were divinely created? Many scientists have tried to calculate the odds of there being intelligent creatures out there, somewhere. Those calculations have spawned a whole new field of science termed exobiology—the sole scientific field whose subject matter has not yet been shown to exist. Let's now consider the numbers that encourage exobiologists to believe in their subject matter. Exobiologists calculate the number of advanced technical civilizations in the universe by an equation known as the Green Bank formula, which multiplies a string of estimated numbers. Some of those numbers can be estimated with considerable confidence. There are billions of galaxies, each with billions of stars. Astronomers conclude that many stars probably have one or more planets each, and that many of those planets probably have an environment suitable for life. Biologists conclude that, where conditions suitable for life exist, life will probably evolve eventually. Multiplying all of those probabilities or numbers together, we conclude that there are likely to be billions of billions of planets supporting living creatures. Now let's estimate what fraction of those planetary biotas include intelligent beings with an advanced technical civilization, which we will define operationally as a civilization capable of interstellar radio communication. (This is a less demanding definition than flying saucer capability, since our own development suggests that interstellar radio communication will precede interstellar probes.) Two arguments suggest that that fraction may be considerable. Firstly, the sole planet where we are certain that life evolved—our own—did evolve an advanced technical civilization. We have already launched interplanetary probes. We have made progress with techniques for freezing and thawing life apd for making life from DNA—techniques relevant to preserving life as we know it for the long duration of an interstellar trip. Technical progress in recent decades has been so rapid that manned interstellar probes surely will be feasible within a few centuries at the very most, since some of our unmanned interplanetary probes are already on their way out of our solar system. However, this first argument suggesting that many planetary biotas have evolved advanced technical civilizations is not a compelling one. To use the language of statisticians, it suffers from the obvious flaw of very small sample size (how can you generalize from one case?) and very high ascertainment bias (we picked out that one case precisely because it evolved our own advanced technical civilization).

A second, stronger argument is that life on Earth is characterized by what biologists term convergent evolution. That is, seemingly whatever ecological niche or physiological adaptation you consider, many groups of creatures have 'converged by evolving independently to exploit that niche, or to acquire that adaptation. An obvious example is the independent evolution of flight by birds, bats, pterodactyls, and insects. Other spectacular cases are the independent evolution of eyes, and even of devices for electrocuting prey, by many animals. Within the past two decades, biochemists have recognized convergent evolution at the molecular level, such as the repeated evolution of similar protein-splitting enzymes or membrane-spanning proteins. It is now difficult to pick up any issue of any journal in any field of biology without encountering further examples. So common is convergent evolution of anatomy, physiology, biochemistry, and behaviour that whenever biologists observe two species to be similar in some respect, one of the first questions they now ask is: did that similarity result from common ancestry or from convergence? There is nothing surprising about the seeming ubiquity of convergent evolution. If you expose millions of species for millions of years to similar selective forces, of course you can expect similar solutions to emerge time and time again. We know that there has been much convergence among species on Earth, but by the same reasoning there should also be much convergence between Earth's species and those elsewhere. Hence although radio communication is one of those things that happens to have evolved here only once so far, considerations of convergent evolution lead us to expect its evolution on some other planets as well. As the Encyclopaedia Britannica puts it, 'It is difficult to imagine life evolving on another planet without progressing towards intelligence.

That conclusion brings us back to the puzzle I mentioned earlier. If many or most stars have a planetary system, and if many of those systems include at least one planet with conditions suitable for life, and if life is likely eventually to evolve where suitable conditions exist, and if about one per cent of planets with life include an advanced technical civilization ~ then one estimates that our own galaxy alone contains about a million P^nets supporting advanced civilizations. But within only a few dozen light-years of us are several hundred stars, some (most?) of which surely have planets like ours, supporting life. Then where are all the flying saucers that we would expect? Where are the intelligent beings that should be visiting us, or at least directing radio signals at us? If intelligent beings from elsewhere had visited Earth after literate civilizations began to develop here several thousand years ago, those beings would probably have searched out the most interesting civilizations on Earth, and we would now have written records of the visit. If the visitors had arrived in the pre-literate or prehuman past, they might have colonized Earth, and we would know of it as an abrupt arrival of drastically different life forms in our fossil record. We are bombarded by Hollywood films depicting such visits, and by tabloids actually claiming them. You will see the headlines at any US supermarket checkout counter: 'Woman kidnapped by UFO', 'Flying saucer terrorizes family', and so on. But compare that pseudo-bombardment, or our expectations, with reality. The silence is deafening. Something must be wrong with the astronomers' calculations. They know what they are talking about when they estimate the number of planetary systems, and the fraction of those likely to be supporting life. I find these estimates plausible. Instead, the problem is likely to lie in the argument, based on convergent evolution, that a significant fraction of biotas will evolve advanced technical civilizations. Let's scrutinize more closely the inevitability of convergent evolution.

This brings me at last to woodpeckers. The 'woodpecker niche' is based on digging holes in live wood and on prying off pieces of bark. It is a terrific niche that offers much more food than do flying saucers or radios. Thus, we might expect convergence among many species that evolved independently to exploit the woodpecker niche. The niche provides dependable food sources in the form of insects living under bark, insects burrowing into wood, and sap. Since wood contains insects and sap all year round, occupants of the woodpecker niche would not have to migrate.

The other advantage of the woodpecker niche is that it provides a terrific place for a nest. A hole in a tree is a stable environment with relatively constant temperature and humidity, protected from wind and j rain and desiccation and temperature fluctuations, and concealed and protected from predators. Other bird species can pull off the easier feat of digging nest holes in dead wood, but there are many fewer dead trees than live trees available. Many other species nest in natural holes, but such holes too are few in number, quickly become known to predators, get reused year after year, and breed infections. Hence it is a big advantage to be able to excavate a clean new nest hole in a live tree, instead of having to use a dead tree or natural hole. Other birds often pay tribute (unsought by woodpeckers) to that advantage, by usurping woodpeckers' holes.

All these considerations mean that if we are counting on convergent evolution of radio communication, we can surely count on convergent evolution of woodpecking. Not surprisingly, woodpeckers are very successful birds. There are nearly 200 species, many of them common. They come in all sizes, from tiny birds the size of kinglets up to crow-sized species. They are widespread over most of the world, with a few exceptions that I shall mention later. They do not have to migrate in winter. Some species have even exploited their woodpecking skills to live in treeless places, excavate nest holes in the ground, and feed on ants. While the earliest known fossil woodpeckers date only from the Pliocene (about seven million years ago), molecular evidence indicates that woodpeckers evolved about fifty million years ago.

How hard is it to evolve to become a woodpecker? Two considerations seem to suggest, 'Not very hard'. Woodpeckers are not an extremely distinctive old group without close relatives, like egg-laying mammals. Instead ornithologists have agreed for a long time that their closest relatives are the honey-guides of Africa, the toucans and barbets of tropical America, and the barbets of the tropical Old World, to which woodpeckers are fairly similar except in their special adaptations for woodpecking. Woodpeckers have numerous such adaptations, but none is remotely as extraordinary as building radios, and all are readily seen as extensions of adaptations possessed by other birds. The adaptations fall into four groups.

First and most obvious are the adaptations for drilling in live wood. These include a strong, straight, chisel-like bill with a hard, horny covering at the tip; nostrils protected with feathers to keep out sawdust; a thick skull; strong head and neck muscles; a broad base of the bill, and a hinge between that base and the front of the skull, to help spread the shock of pounding; and possibly a brain/skull design like a bicycle helmet, to protect the brain from shock. I hese features for drilling in live wood can be traced to features of other birds much more easily than our radios can be traced to any primitive radios of chimpanzees. Many other birds, such as parrots, peck or bite holes in dead Wood. Some barbets can actually excavate in live wood, but they are much more, clumsier, and less neat than woodpeckers and peck from the side rather than straight. Within the woodpecker family there is a gradation of n" ing ability—from wrynecks, which cannot excavate at all, to the many Woodpeckers that drill in softer wood, to hardwood specialists like sapsuckers and the pileated woodpecker.

Another set of adaptations are those for perching vertically on bark, such as a stiff tail to press against bark as a brace, strong muscles for manipulating the tail, short legs, long curyed toes, and a pattern of moulting the tail feathers that saves the central pair of tail feathers (crucial in bracing) as the last to be moulted. The evolution of these adaptations can be traced even more easily than can the adaptations for woodpecking. Even within the woodpecker family, wrynecks and piculets do not have stiff tails for use as braces. Many birds outside the woodpecker family, including creepers and pygmy parrots, do have stiff tails that they evolved to prop themselves on bark. The third adaptation is an extremely long and extensible tongue, fully as long as our own tongue in some woodpeckers. Once a woodpecker has broken into the tunnel system of wood-dwelling insects at one point, the bird uses its tongue to lick out many branches of the system without having to drill a new hole for each branch. Some woodpeckers have barbs at the tip of the tongue to spear insects, while others have big salivary glands to catch insects by making the tongue sticky. Woodpeckers' tongues have many animal precedents, including the similarly long insect-catching tongues of frogs, anteaters, and aardvarks and the brush-like tongues of nectar-drinking lories.

Finally, woodpeckers have tough skins to withstand insect bites plus the stresses from pounding and from strong muscles. Anyone who has skinned and stuffed birds knows that some birds have much tougher skins than others. Taxidermists groan when given a pigeon, whose paper-thin skin tears almost as soon as you look at it, but smile when given a woodpecker, hawk, or parrot. While woodpeckers have many adaptations for woodpecking, most of those adaptations have also evolved convergently in other birds or animals, and the unique skull adaptations can at least be traced to precursors. You might therefore expect the whole package of woodpecking to have evolved repeatedly, with the result that there would now be many groups of large animals capable of excavating into live wood for food or nest sites. Some animal groups defined initially by distinctive ways of feeding have proved to be polyphyletic, meaning that the group is actually an unnatural one, consisting of several groups that evolved similar adaptations from different ancestors. For instance, vultures are now known, and bats and seals are suspected, to be polyphyletic. But all the classical evidence, and now the newer molecular evidence, have uncovered no hint of polyphyly for woodpeckers. Modern woodpecker are all more closely related to each other than to any non-woodpecker. Woodpecking thus appears to have evolved only once.

Picologists, the scientists who specialize in studying woodpeckers, take that conclusion for granted. On reflection, though, it is startling to the rest of us non-picologists who had convinced ourselves that woodpecking would evolve repeatedly. Could it be that other pseudo-woodpeckers did evolve, but that our surviving woodpeckers were so superior that they exterminated their unrelated competitors? For example, separate groups of mammalian carnivores evolved in South America, Australia, and the Old World. But the Old World carnivores (our cats and dogs and weasels) proved so superior that they exterminated South America's carnivorous mammals millions of years ago and are now in the process of exterminating Australia's carnivorous marsupials. Was there a similar shootout in the woodpecker niche?

Fortunately, we can test that theory. True woodpeckers do not fly far over water, with the result that they never colonized remote oceanic land masses like Australia/New Guinea (formerly joined in a single land mass), New Zealand, and Madagascar. Similarly, placental terrestrial mammals other than bats and rodents were never able to reach Australia/ New Guinea, where instead marsupials evolved good functional equivalents of moles, mice, cats, wolves, and anteaters. Evidently it was not so hard to fill those mammalian niches by convergent evolution. Let's see what happened to the woodpecker niche in Australia/New Guinea. We find there a diverse array of birds that evolved convergently to feed on or under bark, including pygmy parrots, birds of paradise, honey-eaters, Australian creepers, Australian nuthatches, ploughbills, ifritas, and flycatchers. Some of those birds have powerful bills used to dig into dead wood. Some of them have evolved elements of the woodpecker anatomical syndrome, such as stiff tails and tough skins. The species that has come the closest to filling the woodpecker niche is not a bird at all but a mammal, the striped possum, which taps on dead wood to detect insect tunnels, rips open the wood with its incisor teeth, then inserts its long tongue or very long fourth finger to pull out the insects.

However, none of these would-be woodpeckers has actually made it into the woodpecking niche. None can excavate live wood. Many are visibly inefficient; I recall seeing a black-throated honeyeater trying to hop up a tree trunk and repeatedly falling off. The ploughbill and striped possum seem to be the would-be's most effective at digging in dead Wood, but both are quite uncommon and evidently cannot make a good wving by their efforts. New Zealand's and Madagascar's pseudo-Woodpeckers are no better. In a stunning instance of convergent Solution, Madagascar's best would-be is also a mammal, a primate called the aye-aye, that operates like a striped possum except for having a very long third instead of a fourth finger. But just as in Australia/New Guinea, none of the would-be's in New Zealand or Madagascar can excavate in live wood.

Thus, in the absence of woodpeckers, many try, and none succeeds. The woodpecker niche is flagrantly vacant on those masses not reached by woodpeckers. If woodpeckers had not evolved that one time in the Americas or Old World, a terrific niche would be flagrantly vacant over the whole Earth, just as it has remained vacant in Australia/New Guinea, New Zealand, and Madagascar.

I have dwelt on woodpeckers at length to illustrate that convergence is not universal, and that not all opportunities are seized. I could have illustrated the same point with other, equally flagrant examples. The most ubiquitous opportunity available to animals is to consume plants, much of whose mass consists of cellulose. Yet no higher animal has managed to evolve a cellulose-digesting enzyme. Those animal herbivores that digest cellulose instead have to rely on microbes housed within their intestines. Among such herbivores, none comes close to achieving the efficiency of ruminants, the cud-chewing mammals exemplified by cows. To take another example that I discussed in Chapter Ten, growing your own food would seem to offer obvious advantages for animals, but the only animals to master the trick before the dawn of human agriculture 10,000 years ago were leaf-cutter ants and their relatives plus a few other insects, which cultivate fungi or domesticate aphid 'cows'.

Thus, it has proved extraordinarily difficult to evolve even such obviously valuable adaptations as woodpecking, digesting cellulose efficiently, or growing one's own food. Radios do much less for one's food needs and would seem far less likely to evolve. Are our radios a fluke, unlikely to have been duplicated on any other planet?

Consider what biology might have taught us about the inevitability of radio evolution on Earth. If radio-building were like woodpecking, some species might have evolved cerUm elements of the package or evolved them in inefficient form, although only one species managed to evolve the complete package. For instance, we might have found today that turkeys build radio transmitters but no receivers, while kangaroos build receivers but no transmitters. The fossil record might have shown dozens of now-extinct animals experimenting over the last half-billion years with metallurgy and increasingly complex electronic circuits, leading to electric toasters in the Triassic, battery-operated rat traps in the Oligocene, and finally radios in the Holocene. Fossils might have revealed 5-watt transmitters built by trilobites, 200-watt transmitters amidst bones of the last dinosaurs, and 500-watt transmitters in use by sabertooths, until humans finally upped the power output enough to be the first to broadcast into space.

But none of that happened. Neither fossils nor living animals—not even our closest living relatives, the common and pygmy chimpanzees—had even the most remote precursors of radios. It is instructive to consider the experience of the human line itself. Neither australopi-thecines nor early Homo sapiens developed radios. As recently as 150 years ago, modern Homo sapiens did not even have the concepts that would lead to radios. The first practical experiments did not begin until around 1888; it is still less than 100 years since Marconi built the first transmitter capable of broadcasting one mere mile; and we still are not sending signals targeted at other stars, though the 1974 Arecibo experiment was our first attempt.

I mentioned early in this chapter that the existence of radios on the one planet known to us seemed at first to suggest a high probability of radios evolving on other planets. In fact, closer scrutiny of Earth's history supports exactly the opposite conclusion: radios had a vanishingly low probability of evolving here. Only one of the billions of species that have existed on Earth showed any proclivities towards radios, and even it failed to do so for the first 69,999/70,000 ths of its seven-million-year history. A visitor from outer space who had come to Earth as recently as the year 1800 AD would have written off any prospects of radios being built here. You might object that I am being too stringent in looking for early precursors of radios themselves, when I should instead look just for the two qualities necessary to make radios, intelligence and mechanical dexterity. The situation there is little more encouraging. Based on the very recent evolutionary experience of our own species, we arrogantly assume intelligence and dexterity to be the best way of taking over the world, and to have evolved inevitably. Think again about that quote from the Encyclopaedia Britannica: 'It is difficult to imagine life evolving on another planet without progressing towards intelligence. Earth history again supports exactly the opposite conclusion. In reality, vanishingly tew animals on Earth have bothered with much of either intelligence or dexterity. No animal has acquired remotely as much of either as have we; those that have acquired a little of one (smart dolphins, dexterous spiders) have acquired none of the other; and the only other species to acquire a little of both (common and pygmy chimpanzees) have been rather unsuccessful. Earth's really successful species have instead been dumb and clumsy rats and beetles, who found better routes to their current c finance.

We have only still to consider the last missing variable in the Green Bank formula for calculating the likely number of civilizations capable of interstellar radio communication. That variable is the lifetime of such a civilization. The intelligence and dexterity required to build radios are useful for other purposes that have been our species' hallmark for much longer than have radios and that will be the subject of the remaining chapters in this book: purposes such as mass-killing devices and means of environmental destruction. We have become so potent at doing both that we are gradually stewing in our civilization's juices. We may not enjoy the luxury of an end by slow stewing. Half-a-dozen countries now possess the means for bringing us all to a quick end, and still other countries are eagerly seeking to acquire those means. The wisdom of some past leaders of bomb-possessing nations, or of some present leaders of bomb-seeking nations, does not encourage us to believe that there will be radios on Earth for much longer.

It was an extremely unlikely fluke that we developed radios at all, and more of a fluke that we developed them before we developed the technology that will end us in a slow stew or fast bang. While Earth's history thus offers little hope that radio civilizations exist elsewhere, it also suggests that any that might exist are short-lived.

We are very lucky that that is so. I find it mind-boggling that the astronomers now eager to spend a hundred million dollars on the search for extraterrestrial life have never thought seriously about the most obvious question: what would happen if we found it, or if it found us. The astronomers tacitly assume that we and the little green monsters would welcome each other and settle down to fascinating conversations. Here again, our own experience on Earth offers useful guidance. We have already discovered two species that are very intelligent but technically less advanced than us—the common chimpanzee and pygmy chimpanzee. Has eur response been to sit down and try to communicate with them? Of course not. Instead we shoot them, stuff them, dissect them, cut off their hands for trophies, put them on exhibit in cages, inject them with AIDS virus as a medical experiment, and destroy or take over their habitat. That response was predictable, because human explorers who discovered technically less advanced humans also regularly responded by shooting them, decimating their populations with new diseases, and destroying or taking over their habitat. Any advanced extraterrestrials who discovered us would surely treat us in the same way. Think again of those astronomers who beamed radio signals into space from Arecibo, describing Earth's location and its inhabitants. In its suicidal folly that act rivalled the folly of the last Inca emperor, Atahuallpa, who described to his gold-crazy Spanish captors the wealth of his capital and provided them with guides for the journey. If there really are any radio civilizations within listening distance of us, then for heaven's sake let's turn off our own transmitters and try to escape detection, or we are doomed.

Fortunately for us, the silence from outer space is deafening. Yes, out there are billions of galaxies with billions of stars. Out there must be some transmitters as well, but not many, and they do not last long. Probably there are no others in our galaxy, and surely none within hundreds of light-years of us. What woodpeckers teach us about flying saucers is that we are unlikely ever to see one. For practical purposes, we are unique and alone in a crowded universe. Thank God!