Shadows of Forgotten Ancestors (51 page)

Vervet monkeys have ventured a little out of the comparative safety of the forest and into the open savanna, where there is less cover for them, and more danger. By playing recordings of their calls back to them, they reveal that they have specific, readily understood alarm cries that elicit specific actions—for a python or black mamba (whereupon all stand on tiptoes and peer anxiously about them in the grass), for a Martial eagle, (whereupon all look up into the sky and dive into deep foliage), and for a leopard (whereupon all quickly scramble up into the trees). Different predators elicit different cries and different evasive behavior. The responses are in part learned. Infants frantically sound the eagle alarm even when a non-raptor is spied flying overhead, and sometimes in response to a falling leaf. Gradually, they get better at making these distinctions. They learn from experience and from others. They have a range of other grunts, some of which scientists think they understand; vervets leave at least a superficial impression of conversing with each other. Gregariousness, by several different routes, spurs social intelligence, which seems to be, of all the species of life on Earth, most highly evolved in the primates.

The vervet fear of snakes is shared by baboons, chimps, and many other primates. You expose wild rhesus monkeys to snakes and objects that look like snakes and they jump out of their skins. Do the same experiment with laboratory-raised rhesus monkeys who have never seen a snake and, although some of them are afraid, you find that they’re much less distraught. In one experiment the wild chimps’ snake phobia became almost manageable when every time the chimp saw a snake it also was offered a banana.
¹¹
So is the fear of snakes not hereditary, but somehow taught by mothers to their babies? Or is there an inborn fear that’s softened in laboratory monkeys because they become habituated to harmless, snake-like objects—hoses, for example? Which is it: heredity or environment? Is knowledge of what a snake looks like, and that snakes mean primates no good, encoded in the DNA? Or are baby primates just watching adults closely and copying what they do?

Almost certainly the answer is a mix between the two. There seems to be an inborn snake-aversion program in the brains of primates. But this is not a closed program, inaccessible to new information from the outside world. Instead it’s an open program that can be modified by experience—for example, “I’ve seen a lot of snakes in my time that don’t do me much harm, so I’ll be a little more relaxed around them,” or, “Every time I see a snake, a banana miraculously appears; snakes have their good points too.” Most primate programs are open, adaptive, malleable, adjustable to new circumstances—and therefore necessarily partaking of ambivalence, complexity, inconsistency.

In a typical modern chronology,
¹²
the line that would lead to us split off from Old World Monkeys about 25 million years (m.y.) ago; from the gibbons, 18 m.y. ago; from orangutans around 14 m.y. ago; from gorillas some 8 m.y. ago; and from the chimps approximately 6 m.y. ago. Bonobos and common chimps went their separate ways only about 3 m.y. ago. Our genus, Homo, is 2 million years old. Our species,
Homo sapiens
, is maybe 100,000 to 200,000 years old—the equivalent of the last day in the life of that fifty-year-old.

Committed to a communal social life, under intense selection pressure from predators, with brains evolving rapidly and education of the young effectively institutionalized, the primates have been developing new forms of intelligence. Their curiosity, experimental bent, and intellectual quickness are partly responsible for their success.

——

Here is an account, by a Japanese primatologist, of a remarkable set of events that transpired in a colony of macaques isolated on a small island called Koshima. Initially, in 1952, there were only twenty of the monkeys; the number almost trebled over the following decade. The natural food supply on Koshima was inadequate, so the monkeys had to be provisioned—with sweet potatoes and wheat dumped on the shore by the primatologists who were observing them.

As anyone knows who’s ever been to a picnic at the beach, sand sticks to food and makes it unpleasantly gritty. In September 1953 a one-and-a-half-year-old female named Imo figured out that she could rinse the sand off her sweet potatoes by dunking them in a nearby brook.

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

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 linguistic 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.