The Ape And The Sushi Master Reflections Of A Primatologist
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The first primatologist to describe the same behavior was Yukimaru Sugiyama, of Kyoto University. Together with a Guinean colleague, Jeremy Koman, Sugiyama found large stones accompanied by smaller ones and empty nut shells in the forest of Bossou, Guinea. In the surface of the larger stones, called platforms, they found shallow cavities indicating that they had been in use for a very long time. In 1979, the two field-workers published a report on twenty-nine cracking sites in the forest and three direct observations of apes placing nuts one by one on the platform and pounding them with smaller stones. These hammer stones weighed under one kilogram but were nevertheless "a little too heavy for the authors' use." Because all of this took place in a dark forest, no photographs could be taken of the chimpanzees actually doing it. For many years, others questioned the observations. 175
Villagers around Bossou use the same technique to open the same nuts. Their cracking tools are indistinguishable from those of the chimpanzees except for generally lighter hammer stones. Human and ape cracking sites are hard to confuse, though, as people rarely venture into the forest and chimpanzees never enter the village. It remains unclear whether the technique could have been transmitted between people and apes, and if so, in which direction. The discoverers go on to observe: "This kind of tool must be almost identical to those by earliest man. Indeed, if they had been found at excavation sites, archeologists almost certainly would have judged them as human stone tools from the unnatural cavities on the pebble tool and platform stone surfaces."
This remark explains the skeptical reception of their findings. Stone tools of any kind used to be attributed without question to humans or their direct ancestors; hence, it was disturbing to hear that there might be other possible producers. We now know much more about nut cracking by chimpanzees, which, because it involves the use of two tools simultaneously in precise coordination, is considered their most complex subsistence technology. Lack of dexterity will result in hurt fingers, escaping nuts, or pulverized contents. First-time human crackers often don't succeed at all. Here is how two primatologists, Christophe Boesch and Hedwige Boesch-Achermann, describe nut cracking deep in the Tai Forest, in Ivory Coast, where chimpanzees use extremely heavy stones to crack the world's toughest nuts, each requiring extraordinary force and an average of thirty-three blows before they give up their prize:
To extract the four kernels from inside a panda nut, a chimp must use a hammer with extreme precision. Time and time again, we have been impressed to see a chimpanzee raise a ten-kilogram stone above its head, strike a nut with ten or more powerful blows, and then, using the same hammer, switch to delicate little taps from a height of only a decimeter. To finish the job, the chimps often break off a small piece of twig and use it to extract the tiny fragments of kernel from the shell.176
But Is It Tool Use, and Do They Need It?
That chimpanzees use such fine coordination, that their cracking sites could be mistaken for those of lithic people, that only certain wild communities know how to crack nuts, that females are better at it than males, and that it takes youngsters many years to acquire the skill-all of this has been learned in the last few decades against the backdrop of earlier claims about tool use as a uniquely human capacity.177 Or, if tools by themselves weren't exclusively human, then at least the manufacturing of tools was. The classical experiments by Wolfgang Kohler on chimpanzees, combined with Jane Goodall's pioneering observations in the field-where she saw chimpanzees modify branches to make them suitable for termiting or chew leaves before using them as a sponge-effectively eroded these claims.178
Yet even today objections can be heard. Incredible as it may sound, tools can be defined in such a way that chimpanzees must be using something else. Some scholars have emphasized that human technology is embedded in role complementarity, symbols, cooperative production, and education. In their opinion, the "tool" label isn't deserved if some or all of these elements are missing, such as when a chimpanzee cracks nuts with rocks, or, I suspect, when a farmer picks his teeth with a twig.179 To draw a clear line is all the more important, according to philosopher Barry Allen, because chimpanzees don't really need their so-called tools. All this talk of ape tools is based on feeble analogies, says Allen, that have nothing to do with our own dependence on technology. In a melodramatic passage, he goes on to bemoan the damage already done to our self-perception:
Belief in the chimpanzee's tool has already proved misleading in the history and philosophy of technology. If it is a scientific fact (as a litany of authorities attest) that chim panzees use tools (real tools, like ours), and if those tools are superfluous, things that chimps could get along without, a possible conclusion is that humans, too, do not really need tools. Technical culture is habitual among us but not an animal necessity, conceivably even superfluous.'8°
Is the human self-image really that fragile? We all realize how essential tools are in our daily lives-we can't even do simple kitchen tasks without them-so why would we, upon hearing that apes in the forest use tools, rush to the conclusion that we don't really need ours? Does the one follow from the other? Apart from this, why would anyone even suggest that apes could easily survive without their tools? It is only from a philosopher's armchair that it is conceivable that wild chimpanzees sit there pounding and pounding, thirty-three blows per nut, for generation after generation, for no good reason at all.181
During peak season at some sites, chimpanzees spend fifteen percent of their waking hours fishing for termites. At other sites, they devote an equal amount of time to cracking nuts. Careful measurements show that they may gain nine times as many kilocalories of energy from this activity than they invest in it.182 Moreover, when Gen Yamakoshi collected information on nut cracking at Bossou, he found nuts to be a keystone resource: they serve as fallback foods when the main source of nutrition-seasonal fruits-are scarce. During the rainy season there are fewer fruits in the trees, which forces the chimpanzees to switch from their usual easy pickings to hard work, devoting almost twenty percent of their foraging time to resources that are inaccessible without tools. Their main fallback foods are palm nuts, which they crack with stones, and palm pith, which they obtain through so-called pestle-pounding. High up in a tree, a chimpanzee stands bipedally at the edge of the tree crown, pounding the top with a leaf stalk, thus creating a deep hole from which fiber and sap can be collected.
These two kinds of food, which are available throughout the year, are exploited whenever fruit production in the forest drops to a low. So, rather than being a leisure activity or hobby, tool technology seems a critical skill. Given that even small differences in food intake are known to affect health, survival, and reproduction, chimpanzee communities with the right technologies enjoy an advantage. Yamakoshi attributes the relatively high reproduction rate of the Bossou population to its effective exploitation of available foods. Naturally, he argues that if indispensability of tools for survival is part of the definition of culture, his chimpanzees should be let in on it.183
Allen's logic that tools must be essential for us, since all human cultures have them, applies equally to the chimpanzee. We know of no wild chimpanzee population without tools; hence, claims of a major difference with the human condition are shaky. It remains possible, even likely, that not each and every known chimpanzee technology contributes to survival. But the salve can be said of our tools, which range from the essential to the trivial. We will return to this issue later on, be cause the claim that apes don't really need their tools, that they use them as toys or gadgets, is a transparent attempt at trivializing what they do. It is part of the myth that we humans have broken with our nature, whereas animals are still stuck with theirs.
Clasping Hands
In 1992, I first saw two chimpanzees at the Yerkes Primate Center's Field Station clasp their hands together. The two were sitting in a climbing frame grooming each other when all of a sudden one female, Georgia, took the hand of another, the older Peony, lifting both of their hands high into the air. They thus
sat in a perfectly symmetrical A-frame posture, each with their free hand grooming the pit of the other's lifted arm.
I recognized the posture from an old article, published in 1978 by two fellow chimpwatchers, William McGrew and Caroline Tutin.184 The article had stayed with me because it was the first description of wild chimpanzee behavior for which I knew absolutely no equivalent in any captive group. Of course, there are other things wild apes do, such as foraging in the trees or fighting with neighbors, that don't occur at zoos or research centers, but that is because conditions don't permit it. All other typical chimpanzee behavior, especially in relation to their socioemotional life, is highly observable. The opposite is also true: behavior first recognized in captivity is sometimes later seen in nature. For example, inspired by my studies at the Arnhem Zoo on reconciliations after fights, there are currently at least three ongoing projects documenting this process in the field. In general, I believe that chimpanzees face, in their social lives at least, basically the same sort of problems in the forest as under enlightened captive conditions. They arrive at the same solutions, whether it be with regard to mother-offspring relations, power politics, or the mutual exchange of favors. Also, their communication, such as vocalizations and facial expressions, is essentially the same under both conditions.
Because of this fundamental similarity, I found it intriguing that wild chimpanzees groomed each other in such an unusual way. But not all chimpanzees do, and this is precisely the point that McGrew and Tutin made in their article. The two investigators were extensively familiar with chimpanzee behavior in Gombe National Park in Tanzania before they visited a different study site, in the Mahale Mountains. There was no reason for them to expect striking differences between the two communities, since they concern the same subspecies of chimpanzee on the same eastern shore of Lake Tanganyika, only 170 kilometers apart. Nevertheless, the Mahale chimpanzees frequently engaged in handclasp grooming, whereas this behavior remains totally unknown in Gombe.
The Mahale research team, led by Toshisada Nishida, was of course familiar with handclasp grooming, but until then they had not realized that they had a unique behavior on their hands. This is why it is so important that field-workers visit each other's sites. If one knows only one community, it is easy to think that its behavior is typical. Based on their visit, McGrew and Tutin were the first to seriously question the assumption of "typical" chimpanzee behavior. They boldly introduced the term social custom to describe the Mahale grooming handclasp.
With this as background, it is easy to see why I was thrilled to discover the very same custom in my own outdoor-housed group of twenty chimpanzees, which made it the first (and thus far only) captive community in the world with confirmed handclasp grooming. The great advantage was that the custom seemed to be in its early stages. Rather than encountering a wild community of chimpanzees that has been doing it for hundreds, perhaps thousands of years, here we had a group in which the behavior was initially extremely rare (only a dozen instances were seen in the entire first year of daily observation) and always initiated by the same individual, Georgia, the presumed inventor.
Georgia is affectionately known as our troublemaker. Born to one of the group's older females, Borie, she loves to stir things up, for example, by starting a screaming match with another female and then withdrawing when the heavyweights get involved. She is the most possessive ape I have ever seen in our food-sharing tests, in which we throw large bundles of branches into the compound. Whereas normally the chimpanzees gather around the possessor of a bundle to beg for a share, if Georgia is the possessor they don't even try, since it is not worth the hassle. So Georgia is a special character, whom I have known since she was little, because about six years before I accepted a position at Yerkes, I had already made a spring visit for a special project. Even though at the time I conducted hundreds of hours of observation, I didn't notice a single grooming handclasp.
Over the years, Mike Seres, my assistant, and I closely followed the spread of the pattern from an occasional handclasp between Georgia and her adult sister or Bone, to handclasps among her family members without Georgia's involvement. Later still, the pattern was also seen among other adults. In 1996, after we removed Georgia for management reasons, handclasping continued. The custom thus exhibited one central characteristic of culture: independence of the originator. When Georgia was returned to the group, years later, the handclasp had become well established in all adults, both males and females.185
The transmission was slow, taking several years, even though the learning process seemed simple. After all, the chimpanzees did not need to learn it from watching others. Most likely, they were first shaped into a handclasp posture by another chimpanzee, who took their hand and moved it up in the air. Nishida compared this to the way some psychologists "mold" gestures of American Sign Language in their apes by bending or moving their hand or arm. Chimpanzees are very sensitive to what others want them to do, such as when one grooming partner decides to move to the shade and literally takes the other by the hand, leading him or her to the desired spot. One will never see such gentle, understanding coordination among monkeys, and it is probably this compliance with others that allows for the dissemination of the handclasp. After having engaged in a number of handclasps, an individual may re-create the same kinesthetic experience with others. Having documented hundreds of handclasps, and having watched a gradual increase in duration of the posture from less than a minute at a time to sometimes over three minutes, we concluded that the spreading was cultural: it traveled along social lines and progressed to include all adult members of the community. It became a group-defining characteristic.
As with secret handshakes in our own societies, the handclasp may even have become a symbol of group membership. I felt this most distinctly when Socko, then a fast-growing adolescent male, returned to the group after an absence of several months. He had battled with the alpha male, Jimoh, and had been removed for treatment of injuries. Upon his return, a pandemonium erupted in which Jimoh tried to attack Socko yet again, but the females jumped to his defense. Fortunately, nothing serious happened, and hours later the entire group gathered on a climber to groom all of the tensions away. The grooming cluster was unusually tight, and I saw Socko move from one partner to another. He was clearly at the center of attention. With each handclasp-and there were many-it was as if the group was confirming that he was one of them, a male who belonged.
The "Bronx Cheer" and Other Local Variants
The preceding descriptions of nut cracking and handclasp grooming represent merely two of many cultural variants in chimpanzees, one with unmistakable survival value, the other with no obvious benefits. New variants are being discovered almost monthly: the charting of chimpanzee culture has obviously only) ust begun.
Much of this work is being done in the field, but studies at zoos have a special place, since the spreading of behavior can be followed in greater detail. In another example, I documented a group of bonobos at the San Diego Zoo that during grooming customarily clapped their hands or feet together, or tapped their chests with their hands. One bonobo would sit down in front of another, clap her hands a couple of times, then start grooming the other's face, alternating this activity with more handclapping. This makes the San Diego Zoo the only place in the world where one can actually hear the apes groom. When new individuals were added, they were said to have picked up the habit in about two years. Since San Diego Zoo has loaned bonobos to other zoos, it would he instructive to follow up on them and see whether they are disseminating the pattern.186
The same bonobos developed special play activities, such as blindman's buff and a game that I called "funny faces." In the first, a juvenile would place an entire arm over his face or poke two thumbs into his eyes and walk around like this high up in a climbing frame, sometimes almost losing its balance or bumping into objects. It was a solitary game, but once one of the juveniles started it, others often followed. The youngest among them didn't really dare and
usually walked around with just one thumb in one eye. The other game consisted of pulling weird faces, which were certainly not part of the species-typical repertoire, with sucked-in cheeks or chewing mouth movements. This game was played by all juveniles. They did not aim these faces at each other, but just sat around grimacing for no reason at all. Since I have never seen anything resembling these games in other bonobos, nor in chimpanzees for that matter, I assume that they are unique innovations of the San Diego colony.187
At Yerkes, we have one chimpanzee group in which many apes loudly splutter their lips during grooming, a behavior rare in some other groups. And a second group, the same one that also does the grooming handclasp, has developed fire-ant fishing. Ant nests in the compound itself never survive the destruction by chimpanzees, but if ants develop a red clay mound outside the fence, the chimpanzees gather long twigs from their enclosure. They poke them through the fence and let the ants walk onto them, after which they eat them off, much like wild chimpanzees do. This is a group activity that has never once been noticed in our other chimpanzees.
In another project by Andrew Marshall and co-workers, the typical, slowly rising hoo-hoo-hoo calls of chimpanzees, known as pant-hoots, were compared between two American zoos. Sonograms showed that adult males at each zoo had a distinct pant-hoot sequence in terms of the number of build-up calls and the duration of the climax yell. Males at each zoo sounded very much like each other but unlike the males at the other zoo. This is remarkable since at each place the males had various origins and hence were unrelated. They must have gone through a process of cultural convergence, resulting in a uniform local dialect. Indeed, one male developed a "Bronx Cheer" variant, which integrated a raspberry-like sound in his hooting. This unique call style was picked up by five other males at his zoo but was never heard at the other zoo.188