Kanzi: The Ape at the Brink of the Human Mind (20 page)

We used slow-motion videotape to study these gestures, and saw clearly that they were not randomly used. There was always a correspondence between the gesture of one individual and the subsequent movement of the partner, indicating a truly abstract communication system. Hand gestures might seem simple, but in fact they demand a high degree of cognitive sophistication. They require a clear concept of self and others. They also require the realization that personal desires can be communicated to another individual. Other requirements are that there be a temporary equivalence between the motion of the hand and the movement of the recipient’s body, and that the hand not be acting as a hand in the instance of gesturing, but as a symbol for the recipient’s body. These skills are often cited as important prerequisites of language. The iconic gestures probably evolved from touch gestures, and their efficacy evokes the sense of a primitive gestural language such as is hypothesized by some to be the beginnings of language in humans.

Bonobos turned out to be unusual not only for their outbursts of sexual activity when food was imminent, but also for the way the food was eaten. When I put food into the group of common chimpanzees I was studying, the largest, most dominant individual (Sonia) hoarded it and refused to share, despite aggressive displays, begging, and temper tantrums by her partners, Phineas and Little One. Only when Sonia was sated did she allow others access to the food. The bonobos’ reaction was quite different. Sexual activity began just prior to the arrival of the food, followed by a frenzy of taking and sharing of food, and many instances of sex being offered in exchange for food. On some occasions Matata, for example, would take food out of Bosondjo’s mouth in mid-copulation. Food sharing does occur among common chimpanzees, but only infrequently and then
mostly between mother-infant pairs and under unusual circumstances, such as meat eating.

Despite the limited and inevitably artificial circumstances of our observations, we learned a lot. In the paper I published with Beverly Wilkerson in 1978, we said: “It is obvious at present, that behaviorally and morphologically,
P. paniscus
appears to be more like
H. s. sapiens
than any other living ape in every aspect of sexuality, from mutual gazing to homosexuality. The use of manual gestures to initiate copulation . . . lends support to this view.”
¹⁷
We suggested that the socio-sexual patterns of the bonobo were an important social phenomenon that served to maintain unusual group stability. We also said that observations of wild populations, which were beginning to bear fruit at the time, would test this idea.

Although the existence of apes has been known for a very long time, systematic studies of natural populations began only recently, instigated by Louis Leakey. In the 1960s, Jane Goodall set up the Gombe Stream research site in Tanzania, to study chimpanzees; Diane Fossey established the Karisoke site in Rwanda, to observe gorillas; and Birute Galdikas went to Tanjung Puting National Park in Borneo to watch orangutans. Studies of the bonobo began a decade later, delayed in part by civil war. Two teams began work in the early 1970s: the Wamba forest team led by Takayoshi Kano, and the Lomako forest team led by Randall Susman. The region where the bonobos live, bounded in the north by the Zaire River and in the south by the Kasai River, is monotonously flat, carpeted with a mosaic of swamp forest and humid forest—and remote.

To reach the region from the United States, Susman and his colleagues must first fly to Brussels for a connection to Kinshasa, Zaire’s capital city. From there to the Lomako forest requires an eight-day riverboat ride, a two-day trip by Land Rover, and a day’s hike through swamp to the research station’s base camp, which consists of several palm-leaf huts. The remoteness of the region explains the outside world’s long
ignorance of the bonobo, and until recently protected the animals from danger by human exploitation.

Making scientific field observations of primates requires a great deal of patience. Initially, you must habituate the animals to a human presence, just as I had done with Lokelema, Matata, and Bosondjo at Yerkes. In the forest, however, it is much more difficult; first, because the forest is dense and the animals are difficult to find, and second, because they can disappear rapidly into the canopy when frightened. The Japanese and American teams followed different practical strategies to habituate the groups of chimps they planned to study. Susman and his colleagues followed the “purer” route of patience, patience, and more patience, while Kano and his associates elected to entice the animals to a convenient location by provisioning them. They did this by clearing a small area of forest used by a bonobo group, and then occasionally putting out sugar cane, which the chimps love.

The method has the advantage of quickly getting animals to a location where you can observe them, but purists argue that the animals’ behavior may be altered in subtle ways by the artificiality of the situation. As a result, Kano was able to collect more data, and more quickly, than Susman and his colleagues. Since there appears to be no significant difference in observed behavior between the Lomako and Wamba forest groups, Kano feels justified in his pragmatic approach. He points out that as long as the amount of food used is minimal, the apes treat the observation site as simply another place in the forest where they can locate food.

The social life of common chimpanzees, as mentioned earlier, is dominated by males. Social groups are relatively small, with perhaps thirty individuals, and loosely organized. Females with their offspring frequently forage alone, or in the company of a few other females, and over a limited range. Bands of mature males patrol the ranges of several females or groups of females, effectively herding them as their possessions and defending them from the attention of males from neighboring groups. The females generally leave their natal groups at adolescence, to spend the rest of their lives in another group. This
means that male chimps in a social group are likely to be close kin—brothers and cousins. This kinship is a clear asset in establishing the strong bond that keeps the males together as an effective unit; they defend their females and procure new ones by raiding other groups. These intergroup clashes are extremely violent, and researchers at Gombe have recorded many bloody deaths as a result of them. For instance, one group split in two between 1970 and 1972, forming the Kasekela and Kahama groups. Over the next five years, six of the seven males in the Kahama group were attacked and killed one by one by Kasekela males.

Common chimp males are also aggressive within their own group, killing and cannibalizing infants on occasion. Infanticide of this sort often occurs when the mother is a recent transfer into a new group and her infant is likely to have been fathered by a male in her previous group. Such infanticide is seen by evolutionary biologists as benefiting the males in the new group by making the mother again receptive, this time to one of them. However, there are clear instances of infanticide among common chimpanzees in which the female had not recently transferred and the father of the infant was almost certainly one of the males participating in the cannibalization. Typically, these cannibalized infants are male and the taking of the infant from the mother seems to be preceded by generalized aggressive arousal among the males. Infanticide has also been reported among common chimpanzee females, and in such cases the benefits are more difficult to explain.

In all the years of observation at Wamba and Lomako, no example of murder or infanticide has been seen. This is despite the fact that bonobos live in much larger, more closely associated groups, sometimes with as many as a hundred individuals. In larger groups the opportunity for aggression is heightened, but bonobos have found a way to avoid it. The way, it seems, is to follow the 1960s dictum, “make love not war”—literally. The prevalent sexuality that I saw in the artificial settings of Yerkes and the San Diego Zoo operates just as much in the natural populations, and it acts to defuse potential aggression in all combinations of the sexes. “In pygmy chimpanzee society, the
primary role of copulatory behavior is undoubtedly to enable male-female coexistence, not to conceive offspring,” says Kano. “Here, copulation goes beyond reproduction.”
¹⁸
The same may be said about homosexual behavior—that the primary role is social cohesion. As a result, says Kano, “the pygmy chimpanzee lives in a much more peaceful and mutually tolerant society than the common chimpanzee, its sibling species.”
¹⁹

The reason that bonobos often aggregate in such large groups is the nature of their food resources. Although their diet includes more than a hundred different species of food items, fruit is important among them. And the forest has many large trees that offer a huge food resource when they come into fruit. They are, however, spread apart in time and space. “Faced with scattered but concentrated food resources, pygmy chimpanzees improve their efficiency more by forming large parties than by separating into small parties,” explains Kano. “To maintain a large size party, however, individuals must be able to coexist.”
²⁰
The high rate of sexuality among bonobos, with its humanlike aspect, is therefore likely to be the evolutionary product of adaptation to the particular nature and distribution of food resources.

Bonobo social groups are more closely associated and stable than those of common chimpanzees. Males and females occur in about equal numbers, as opposed to the imbalance in favor of females in common chimp groups. And, in general, bonobo males are less tightly bonded together than common chimps, and females more so. One reason for this is that, again, unlike the pattern in common chimpanzees, male bonobos remain closely affiliated with their mothers, long into adulthood. “In this way, the mother is the core of pygmy chimpanzee society, and the males lead a life following their mothers,” observes Kano.
²¹
This same factor contributes to the much more equal status between male and female bonobos, in contrast with common chimps. Also, the closer bond among female bonobos allows them to form alliances to ward off any aggression from males. The overall more egalitarian tenor of bonobo society is reflected in the body size of males and females. In common chimps, where the males effectively compete with each
other for access to females, males are about 15 to 20 percent bigger than females. (Such a size difference is common in species where males compete for females.) Male bonobos, by contrast, are only fractionally bigger than their potential mates.

Dominance hierarchies are not completely absent among bonobos, but they are more subtle and more fluid than in common chimps. “The breadth of variation in personality among pygmy chimpanzees is so great that a simple graphical representation of the dominant-subordinate relationships between individuals cannot be drawn,” says Kano. “There is evidence, however, that pygmy chimpanzees do not have a strictly linear rank order.”
²²
The unusual influence of females in the society, combined with sometimes elaborate alliances between individuals, all too readily disrupts what fragile dominance hierarchy does exist.

Watching bonobo behavior in the wild is a beguiling experience, and it is easy to anthropomorphize, but the many humanlike qualities of these fascinating animals seems to demand it. Kano tells of many such experiences. When he was documenting the bonobos’ food resources, he was surprised by the attention the chimps gave to earthworms. He often watched them dig diligently for hours in swamps, yielding a meager reward for their efforts. Sometimes, for instance, an efficient digger found a worm on average every twenty-five minutes. The bonobos at Wamba are not forced to forage at the margin of poor returns—they eat well there. It seems to be something of a leisure pursuit, observes Kano: “The activity resembles a household of people who leave for the coast on an occasional holiday, amusing themselves gathering shells at low tide and happily returning with a cupful of short-neck clams. In other words, it may be recreation. ... It is hard to accept that the merit of this habit is the slippery sensation when the earthworm passes down the throat.”
²³

One of the most intriguing observations at Wamba is branch dragging, an activity that involves technology and communication. Almost exclusively an activity of adult males, it appears to be a way of organizing the movement of the group on its day’s activity. It therefore has elements of symbolism to it,
much like the honeybees’ dance. Sometimes an individual will grab a branch and drag it around boisterously, as an element of display. More often, and more interestingly, however, branch dragging is a prelude to group movement.

The individual often spends as much as half an hour searching for the “right” branch, frequently rejecting inferior ones. What criteria are being employed, no one knows. Then the chimp runs through the forest dragging the branch behind him, which creates a great noise and catches group members’ attention. He might run back and forth several times, and he is sometimes accompanied by other males, also branch dragging. Finally, the entire group sets off into the forest—significantly, following the direction described by the branch dragging. Once the group is on the move, branch dragging stops. But if, for some reason, a decision is made suddenly to take a different direction from the one originally planned, the males leading the group will indulge in a burst of branch dragging, describing the new direction to be followed. Usually, a bonobo group on the move is relatively quiet. It is only when they reach a fruiting tree that a great vocal outburst erupts, an accompaniment to enthusiastic sexual activity.