Shadows of Forgotten Ancestors

by Carl Sagan

  After 1959, features of information transfer changed. Sweet potato washing was no longer a new mode of behavior: when infants were born, they found most of their mothers and elders washing potatoes and learned this behavior from them as they learned the group’s usual food repertoire. Infants are taken to the edge of the water during the period when they are dependent on mothers’ milk. While their mothers wash potatoes, infants watch carefully and put into their mouths pieces of potatoes that mothers drop in the water. Most of the infants acquire potato washing around 1 to 2.5 years old …

  [I]n the second period (1959-present, the period of “precultural propagation”), acquisition of potato washing occurred independent of sex and age. During the second period, virtually all individuals … acquired this habit through their mothers or playmates when they were infants or juveniles.

  But there was still the problem of sandy wheat—until Imo’s second epiphany:

  In 1956, when Imo was 4 years old, she took a handful of mixed wheat and sand to the brook. When it was dropped on the water, the sand sank and the floating wheat could be skimmed off the water’s surface, now clean again. This “placer-mining” technique* was also adopted by some of the other monkeys, and soon more and more animals learned it …

  Compared to potato washing, placer mining was quite slow to propagate …

  Placer mining appears to require more understanding of complex relations between objects and may be particularly difficult to learn because a monkey must “discard” his food first, while in potato washing he can keep the potato from the beginning to the end.13

  Imo was a primate genius, an Archimedes or an Edison among the macaques. Her inventions spread slowly; macaque society, like traditional human societies, is very conservative. Perhaps the fact that she came from a high-ranking family in a species given to hereditary matriarchy aided acceptance. As is usually true, adult males were the slowest to catch on, obstinate to the last; a female invented the process, other females copied her, and then it was taken up by youngsters of both sexes. Eventually, infants learned it at their mother’s knee. The reluctance of the adult males must tell us something. They are fiercely competitive and hierarchy-ridden. They are not much given to friendships or even to alliances. Perhaps they felt impending humiliation—if they were to imitate Imo, they would be following her lead, becoming in some sense subservient to her, and thereby losing dominance status. They would rather eat sand.

  No other group of macaques anywhere in the world is known to have made such inventions. By 1962, it is true, macaques on other islands and the mainland, recently provisioned with potatoes, began washing their food before eating it. But it is unclear whether this was due to independent invention or to cultural diffusion: In 1960, for example, Jugo—a macaque who had become adept at washing potatoes—swam from Koshima to a nearby island where he stayed for four years and may have trained the resident macaques.14 Perhaps there were other macaque Archimedes; perhaps not. Imo is the only one we know for certain.

  It took a generation for these two obviously useful inventions to become widely accepted.15 The conservative, near immobility of popular prejudice, the reluctance to adopt a new practice even if its advantages are clear, is a tendency not restricted to Japanese macaques.16 Perhaps the stolidity of the adult males is partly a matter of learning abilities declining with age. Human teenagers seem so much more adept than their parents at, say, operating a personal computer or programming a videocassette recorder. But this doesn’t explain why adult female macaques learned so much more readily than their male counterparts.

  We can see how such inventions made in different, nearly isolated, groups can lead to cultural differentiation even in monkeys. A much more innovative species of primate, in which various groups are in occasional contact, conflict, or competition, might, we would guess, devise spectacular new forms of culture and technology.

  ——

  An early Algerian myth held that long ago apes could talk, but were rendered mute for their transgressions by the gods. There are many similar stories in Africa and elsewhere.17 In another widespread African story, apes can talk, but prudently refuse to do so—because talking apes, their intelligence in this way made manifest, will be put to work by humans. Their silence is proof of their intelligence. Occasionally the indigenous people would introduce a visiting explorer to a chimp with many remarkable skills and tell him that it could also speak. But, at least while the explorer was there, none ever did.

  Lucy was a chimpanzee celebrity. She was one of the first of the apes to learn to use a human language. The mouth and throat of the chimp are not configured for speech as ours are. In the 1960s, the psychologists Beatrice and Robert Gardner wondered whether chimps might be intellectually capable of language but prevented from speaking by the limitations of their anatomy. Chimps have phenomenal dexterity. So the Gardners decided to teach a chimp named Washoe a gestural language, Ameslan, the American sign language used by hearing-impaired humans. Here each gesture can represent a word, rather than a syllable or a sound, and in this respect Ameslan is more like Chinese ideograms than the Greek, Latin, Arabic, or Hebrew alphabets.

  Young female chimps proved to be adept pupils. Some of them eventually acquired vocabularies of hundreds of words. Julian Huxley—T. H. Huxley’s grandson, and a leading evolutionary biologist—had argued that “plenty of animals can express the fact that they are hungry, but none except man can ask for an egg or a banana.”18 Now there were chimps eagerly requesting bananas, oranges, chocolate candies, and much else, each represented by a different sign or symbol. Their communications were often clear, unambiguous, and apparently in context, as has been attested to by delighted audiences of hearing-impaired people watching films of signing chimps. They were able, it is said, to use their signs in a fairly consistent elementary grammar, and to invent from the words they knew phrases that they had never before encountered. Chimps were found to generalize a word such as “more” into new contexts—such as “more go” and “more fruit.”19 A swan evoked the spontaneous neologism, in independent and widespread use among humans, “water bird.”

  Lucy was one of the first. It was she who signed “candy drink” after first tasting a watermelon, and “cry hurt food” after her first experience with a radish. She became, it is said, able to distinguish the meaning of “Lucy tickle Roger” from “Roger tickle Lucy.” Tickling is close to grooming. When idly turning the pages of a magazine, Lucy made the sign for “cat” when she turned to a picture of a tiger, and “drink” when she came upon a wine advertisement. Lucy had a human foster mother; she was, after all, only a few years old during the whole of her laboratory experience with language, and young chimps especially crave emotional support. One day, when her foster mother, Jane Temerlin, left the laboratory, Lucy gazed after her and signed, “Cry me. Me cry.”

  Ameslan-literate apes have often been spied signing to themselves when they thought no one else was present. Perhaps this was just wordplay, trying to get the new skill down pat. Or perhaps it was an experiment to see if they could conjure “fruit,” say, out of the air with no humans present, just by producing the right words. It had worked well enough when humans were around.

  To what extent Lucy and her fellows understood the gestural language they were using, and to what extent they were merely memorizing sequences of signs whose true meaning they failed to grasp, is a subject of scientific debate. To what extent young humans learning their first language do the one or the other is also subject to debate.

  Perhaps only the hits were recorded and not the misses; that is, maybe Lucy and other chimps judged Ameslan-literate generated a wide range of signs more or less at random which, when they made contextual sense, were written up by the human observers and discussed at scientific meetings, but which, when irrelevant or unintelligible, were ignored. This is the anecdotal fallacy* that haunts this branch of science. But the anecdotes are plentiful and striking.

  One of the most thoroughgoing examinations of the lingu
istic and grammatical abilities of apes was done by the psychologist Herbert Terrace and his colleagues, who recorded on videotape nearly twenty thousand signing attempts generated by a male chimp named Nim.20 He mastered over one hundred different gestural signs. Nim would regularly sign “Play me” or “Nim eat” in context and with apparent understanding. But there was no evidence, Terrace concluded, that Nim put more than two signs together in any consistent manner appropriate to the context. The average length of his sentences was less than two words long. His longest recorded sentence was “Give orange me give eat orange me eat orange give me eat orange give me you.” It does seem a little frantic, but oranges are tasty, chimps are not known for their patience, and anyone who has spent time with a small excited child will recognize the syntax. Note that four of the words are non-redundant (“give me orange you”), and that no words irrelevant to this urgent request are included among the sixteen. Emphasis through repetition is common in human languages. But the simplicity of chimp sentences has rendered their use of language unimpressive in the minds of many psychologists and linguists. Nim was also belittled for interrupting his trainers’ signing with his own, for being too imitative (repeating remarks of his trainer), and for not inventing grammatical rules such as the subject-predicate sequence.

  This work has in turn been criticized. Chimps require close emotional ties for social tasks and, one would think, especially for something as difficult as language; instead, Nim had sixty different trainers over a four-year period. There is a tension between a loving, one-on-one environment that might be needed to teach language skills and the emotionally sterile protocols needed so that scientific results are, with high reliability, uncontaminated by the enthusiasm of the experimenters. It has frequently been found that apes sign most creatively in spontaneous circumstances in their everyday life, and not in experimental sessions. Too, there was great emphasis on drill in the Nim experiments, the very opposite of spontaneity. The complaint about Nim interrupting the signing of his trainer has itself been belittled, because Ameslan speakers may sign simultaneously without stepping on each other’s lines, an advantage of signing over speech. Delayed imitation is just what human children do when they first learn language. For all these reasons, just how much grammatical dexterity apes have is still an open question.21

  But clearly chimps can use something like the rudiments of language with much greater facility than had been thought possible before the experiments of the Gardners. They can unambiguously associate certain signs with certain people, animals, or objects—unsurprising when there are monkeys with different alarm cries and evasion strategies for different species of predators. Chimps have mastered an elementary vocabulary of a few hundred words, comparable to what a normal human two-year-old can do. Chimps who have some knowledge of these signs and who are raised together have been known spontaneously to sign to one another. There is at least one case in which a young chimp, uninstructed by any human, is said to have learned dozens of signs from another chimp knowledgeable in Ameslan.22

  “We may consider it proven,” said the psychologist William James, “that the most elementary single difference between the human mind and that of brutes lies in this deficiency on the brute’s part to associate ideas by similarity.” He held this to be a more fundamental cause of human uniqueness than reason, language, and laughter—all of which, he taught, emerge from recognizing similarities among ideas.23

  Some chimps were taught a common symbol to describe any one of three foods, and another to describe any one of three tools. Then they were taught the individual names of other foods and other tools and asked to put them in the proper categories—not the new foodstuffs or tools themselves, but the arbitrary names of the new foodstuffs and tools. They did exceptionally well.24 How is this possible, unless chimps reason, form abstract ideas, and “associate ideas by similarity”? Another domesticated chimp, Viki Hayes, was given two piles of pictures, one of humans, the other of nonhumans, and then handed a stack of additional pictures and invited to categorize. Her performance was perfect, with one small exception: She placed the picture of herself among the humans.

  The psychologist Sue Savage-Rumbaugh25 and her colleagues devised a keyboard with 256 lexigrams on its two sides. Each lexigram stands for something of interest to a chimp—“tickle,” “chase,” “juice,” “ball,” “bug,” “blueberry,” “banana,” “outdoors,” “videotape,” and so on. The lexigrams do not depict their referent; rather, they show geometrical or abstract figures that only by arbitrary convention are connected with what they stand for. The scientists tried to teach this lexigraphic language to an adult bonobo, but she was an indifferent student. Her six-month-old son, Kanzi, often accompanied his mother to these training sessions and was mainly ignored by the scientists. Two years later, having observed the laboratory routine in depth but never having been trained (for example, by being given a banana for typing the banana lexigram), Kanzi demonstrated that he was learning what they were trying to teach his mother. (His interest eventually became hard to miss: He would leap on her hand, her head, or the keyboard at the moment she was about to select a lexigram.) The focus of the study switched to him.

  By age four he had mastered the board, and would routinely use lexigrams to request, confirm, imitate, choose an alternative, express an emotion, or just comment. He would indicate a future course of action and then do it. In combining two action lexigrams, he would predict (or better, reveal) the impending sequence of events; if he typed “chase, tickle” he would chase and then tickle the experimenter or another chimp, and only very rarely tickle before chasing. Kanzi typed “hide peanut,” and then did just that. It seems hard to deny that Kanzi has a mental image of his intended future actions, and in appropriate sequence. As time went on, he developed other grammatical rules, especially putting the action before the object, rather than vice versa (“bite tomato,” rather than “tomato bite”). Inventing grammar is much more impressive than merely being taught it.

  Still, after some years about 90% of Kanzi’s utterances were only a single symbol;* rarely did they comprise more than two symbols. This is the same pattern found for Nim. Perhaps we are coming up against some fundamental limitations in chimp capacity for language.

  Kanzi has shown, again via an accidental discovery, that he can understand hundreds of words of spoken English. Place earphones on his head, situate yourself in another room, make a request of him through a microphone, and the video camera reveals him doing what he is asked. Done this way, no gestural cues can be unconsciously communicated from human to ape. Typical of over 600 novel requests, perfectly complied with, were “Put the backpack in the car,” “Do you see the rock?… Can you put it in the hat?” “Take the mushrooms outdoors,” “Knife the orange,” “Eat the tomato,” and “I want Kanzi to grab Rose.” Even some of Kanzi’s errors are not so bad. Asked “Can you put the rubber band on your foot?” he promptly put it on his head.26 His performance was comparable to that of a 2½-year-old human who was tested in the same set of experiments. Other bonobos are also found to understand spoken English.

  Kanzi loves to play ball. Hide a ball in one of seven designated sites in the laboratory’s fifty-five-acre forest, tell him by lexigram or spoken word where the ball is, and Kanzi with high accuracy makes for the site, searches, and finds the ball.27 In this case there is a reward for understanding spoken English. But in most cases Kanzi receives no reward except the approval of humans and perhaps some gratifying sense of the power of communication. The motives of a young child learning language may not be very different.

  In a different laboratory, a chimp named Sarah was able to recognize that red characterized an apple more than green did (she had not been exposed to the Granny Smith variety), and a square with a stem was a better representation of an apple than a square without a stem. She was also able to associate the words for each of these properties of an apple with the word for apple—and these words were not in Ameslan, but in a symbolic language of plastic to
kens she had been taught, the tokens not resembling the objects in question.28 (“Apple,” for example, was represented by a small blue triangle.) How is this possible, unless chimps are able to abstract and categorize?

  Other experiments have shown chimps capable of reasoning by analogy and by transitive inference, described by the discoverers of this aspect of chimp thought as “ ‘A r B, B r C, therefore A r C,’ where r is some transitive relation, such as greater than.”29 (There may, for all we know, be critics who do not even understand the preceding sentence but who deny that chimps reason.) Still other experiments have been interpreted as showing that chimpanzees impute states of mind to others, or, as the psychologists David Premack and G. Woodruff put it, that chimps have “a theory of mind.”30

  Where chimps are linguistically deficient, at least so far, is in grammar and syntax. They are bereft of subordinate clauses, articles and prepositions, tenses, conjugation of verbs, and the like—as are small humans first learning language. The absence of such grammatical machinery prevents the lucid expression of even fairly simple ideas; misunderstandings tend to accumulate. Compounded by small vocabularies, it’s a little like a middle-aged American, relying on barely remembered high-school French, attempting to be understood in rural Provence. A better analogy might be the “pidgin” languages that emerge at the interface between two or more fully realized but very different human languages; despite their linguistic facility, the speakers revert to something like chimpish. Oddly, no one has made a serious and systematic effort to teach apes grammar and syntax,31 so we can’t be sure it’s beyond their reach. “Until then,” writes a modern linguist, “one cannot entirely close off the possibility, unlikely as it may be, that apes could acquire language in its fullest sense.”32