Kanzi: The Ape at the Brink of the Human Mind

by Sue Savage-Rumbaugh

  Yerkes reported that both chimps displayed a range of humanlike facial expressions, but noted that this was particularly developed in Chim. Chim was also given to “pronounced laughter” as a way of expressing satisfaction and joy. On one occasion, Chim is said to have displayed his friendly nature by plucking some flowers and giving them to “a lady attendant.” Both apes loved being out-of-doors, and they tumbled with abandon. “Frequently Chim would stretch out on his back in the pasture and with his hands under his head bask in the sunshine,” wrote Yerkes. “It was strikingly suggestive of a human attitude of relaxation.”3 Apparendy, Panzee never assumed such an attitude. “Never have I seen a man or beast take greater satisfaction in showing off than did little Chim. The contrast in intellectual qualities between him and [Panzee] may briefly, if not entirely adequately, be described by the term ‘opposites.’”4

  There are differences in personality among bonobos and common chimps, of course, so that Yerkes’ comparison of Chim and Panzee may exaggerate the species’ differences in general. Not all bonobos are intellectual geniuses, as Chim apparently was. Nor are all chimps dull-witted as Yerkes described Panzee. Overall, however, it is impossible to spend more than a few hours around the two species without being overwhelmed by the differences between them and the uncanny echoes of humanity one constantly experiences with the bonobo.

  Yerkes, a professor of psychology at Yale University, had acquired Chim and Panzee from the New York Zoological Park and studied them for about a year. Chim died in July 1924, from pneumonia. Bonobos had not been recognized as a distinct species at this time. Reports of the existence of these unusual chimpanzees, living south of the River Congo (now the Zaire River), had only recently begun to reach the West, and few animals had been brought out. Scholars had known of the existence of apes since the seventeenth century, and the first scientific description of the chimpanzee was drafted in the late eighteenth century. For the existence of a species of ape to remain unknown for a further century and a half is a remarkable piece of scientific history. Consequently, the eventual discovery of the species was “one of the major faunistic events of the 20th century,”5 as Dirk Thys van den Audenaerde, of the Tervuren Museum, Belgium, put it recently.

  The first scholar to recognize the distinctive nature of the pygmy chimpanzee was Harold J. Coolidge, a zoologist at Harvard University. In 1926 and 1927 Coolidge was part of a university expedition to the eastern Belgium Congo (now Zaire), to collect gorilla material for the Museum of Comparative Zoology. The following year he visited European museums, including the Tervuren Museum, to gather yet more data on gorillas. Coolidge recently described his moment of discovery: “I shall never forget, late one afternoon in Tervuren, casually picking up from a storage tray what clearly looked like a juvenile chimp’s skull from south of the Congo and finding, to my amazement, that the epiphyses were totally fused.”6 In other words, the skull, though small, was that of an adult. Coolidge found four additional skulls, all small, all adult. He made measurements and planned to write a scientific paper that would report the discovery of a previously undescribed form of chimpanzee.

  Two weeks later the German anatomist Ernst Schwarz visited Tervuren and, prompted by Henri Schouteden, the museum’s director, examined the same material that had so excited Coolidge. “In a flash Schwarz grabbed a pencil and paper, measured one small skull, wrote up a brief description, and named a new pygmy chimpanzee race: Pan satyrus paniscus,” recalls Coolidge. “He asked Schouteden to have his brief account printed without delay in the Revue Zoologique of the Congo Museum. I had been taxonomically scooped.”7 For a zoologist, the naming of a new species is an important event, happening only once or twice in a career, if at all. Coolidge had apparently missed his chance, and so too had Schouteden, in whose charge the skulls had been for some years. In fact, Schwarz had thought the skulls represented only a subspecies, making it zoologically intimate with the common chimpanzee, which carried the subspecies name Pan satyrus troglodytes.

  Coolidge continued his studies and in 1933 published a major scientific paper that raised what he called the “pygmy chimp” to the status of a full species, simply Pan paniscus. In that paper, he suggested that the pygmy chimpanzee “may approach more closely to the common ancestor of chimpanzees and man than does any living chimpanzee hitherto discovered and described.”8 This insightful comment lay unheeded for three decades.

  In 1954 two German biologists, Edward Tratz and Heinz Heck, suggested that not only was the pygmy chimpanzee different enough to deserve the status of a full species, but that it was so different that it should be accorded a separate genus. The name they offered was Bonobo paniscus. They chose Bonobo, they explained, because it was the native word for “chimpanzee.” In fact, no such word has yet been found to exist among the dialects of the people in Zaire, which is home to the pygmy chimpanzee. It has been suggested that the word may be a distortion of the town “Bolobo,” a village where chimpanzee specimens had been collected in the 1920s. Tratz and Heck’s call for separate genus status was not widely accepted, but the word bonobo has become commonly used as a synonym for pygmy chimpanzee.

  The bonobo is not a true pygmoid form of the common species. While it is slightly smaller than the chimpanzee, weighing on average 84.5 percent of the larger species, the significant difference is in overall body shape. Bonobos have a more graceful build, relatively longer legs, and a smaller skull with a high forehead and an extremely expressive dark face. Because of their higher center of gravity, narrow chests, and more vertically mounted skulls, bonobos are able to walk bipedally more easily than the common chimp, a behavior that adds to their humanlike aspect. In particular, when you see a bonobo walking on two legs, as humans do, you get a strong impression of what the human ancestor would have looked like, as Coolidge suggested.

  This impression was cast in more scientific terms during the 1960s and 1970s when four researchers brought together three different lines of evidence in its support. From the evidence of molecular biology, the chimpanzee’s anatomy, and what is known of the anatomy of the earliest members of the human family, the researchers concluded in a landmark paper in 1978 that “among living species, the pygmy chimpanzee offers us the best prototype of the prehominid ancestor.”9 The “prehominid ancestor” referred to would be a creature that predated the lineages that eventually led to modern chimpanzees and modern man.

  Since Darwin’s time, many creatures have been proffered as suitable “models” for the common ancestor, including the tarsier (a shrewlike primate), the monkey, the gibbon, and the African apes, particularly the chimpanzee. Yet there are potential traps awaiting those bold enough to attempt to reconstruct a missing piece of prehistory by looking to a living species as a model. One of these is the dangerous assumption that extinct species may be just like extant species. As Charles Darwin cautioned in his 1871 book, The Descent of Man, “We must not fall into the error of supposing that the early progenitor of the whole Simian Stock, including man, was identical with, or even closely resembled, any existing ape or monkey.”10

  By the 1970s, however, evidence from molecular biology clearly linked humans with African apes. Discoveries of human fossils, some more than three million years old, also displayed apelike aspects, particularly as regards the skull, face, and jaws. Such finds made it more plausible to look to African apes for clues to the anatomy and behavior of the common ancestor.

  The earliest known species identified as a member of the “human family,” Australopithecus afarensis, was essentially an ape that walked upright. Fossils dating back to more than three million years from Ethiopia and Tanzania reveal a head that was extremely apelike, with a small brain and protruding face. The most famous fossil is a partially complete skeleton of a three-foot-tall female, which was named Lucy by its discoverer, Donald Johanson. Although Lucy’s gait was more upright, or bipedal, as indicated by the anatomy of her pelvis and legs, she displayed many apelike characteristics. For instance, in man the legs are much longer than t
he arms, while in apes the reverse is true. Lucy was intermediate between human and ape. The bones of her hands and feet were curved as well, suggesting that she spent a good deal of time in the trees climbing on branches. These apelike features suggested to many anthropologists that even though Lucy may have walked bipedally, she was, unlike ourselves, also a most adept tree climber. The popular impression of the earliest human progenitor is that of an ape-man striding bipedally onto the open savannah. However, it is almost certainly the case that this progenitor lived in a mosaic of woodland and forest and that it often had to climb trees as well as walk upon the ground.

  Randall Susman, who has studied both wild populations of bonobos in Zaire and the anatomy of early hominids, notes that there are many adaptations for forest life in the skeletons of our progenitors. To the extent that the earliest human species were at least partial forest dwellers, it becomes even more reasonable to search for clues to our ancestor’s behavior by studying modern forest-dwelling apes. The bonobo is the most forest adapted of the African apes, and is therefore a potential source of those clues to ancient behavior.

  It is not just the habitat in common with afarensis that makes the bonobo a plausible model for the common ancestor. In 1982, Adrienne Zihlman, an anthropologist at the University of California, Santa Cruz, drew a now famous picture of a composite skeleton, with the right side that of a bonobo and the left side that of Lucy. The head, face, and jaw are strikingly similar between the bonobo and afarensis, except for somewhat smaller teeth in the human fossil. In the rest of the skeleton, the only evident difference is in the pelvis: The chimpanzee’s is long, as an adaptation to quadrupedal locomotion, while that of afarensis is squat, as adapted to bipedalism. Aside from this, however, there is a close match between the two. The drawing clearly makes a powerful visual argument for the so-called pygmy chimpanzee hypothesis.

  The hypothesis generated tremendous interest in the bonobo, and also provoked criticism. One criticism was that common chimps and bonobos are closer to each other genetically than they are to humans. The critics therefore asked: How could either species be a better model for an ancestral form? Zihlman responded in the following way: “The evolutionary question … is not whether one chimp is more closely related to us than the other is, for we know they are closer to each other than to humans. The question is, has one chimp species remained more similar to the ape-human ancestor, a ‘living link,’ while the common chimp and the hominids have undergone more morphological change?”11

  In a more recent study, Henry McHenry, of the University of California, Davis, compared the anatomy of the common and pygmy chimpanzee, the gorilla, the orangutan, and Australopithecus. He confirmed some of the similarities between the bonobo and the human fossil, but pointed out that the bonobo did not have exclusive claim on the match. The shoulders, feet, and overall body proportions of the bonobo were the best match for the fossil human, but the common chimp is a better match for one of the arm bones (the ulna), the orangutan is better for the lower end of the thigh bone, and the gorilla for part of an arm bone. “The obvious conclusion from this is that the common ancestor of the African [apes and humans] was not precisely like any modern [ape] and its reconstruction must derive its form from clues provided by all extinct and extant [apes and humans],” concluded McHenry.12

  McHenry’s view becomes a more sophisticated version of the ancestral ape hypothesis, implying that we have lessons to learn about ourselves from all living apes. However, in the short time that bonobos have been studied, both in captivity and in the wild, it has become evident that Yerkes’ impression of a humanlike aspect to the species was correct. In this context, therefore, the bonobo is clearly the best choice among living apes as an ancestral model, and as such represents an important source of understanding about our prehistory.

  Ironically, just as the world of science is becoming aware of the bonobo as a unique intellectual resource, the species is being pushed rapidly toward extinction. Bonobos live only in a small region of central Zaire bounded by the Zaire and Kasai Rivers. The area is rich in wildlife, including elephant, the okapi, the bongo, the forest buffalo, the duiker, and the l’Hoest and Hamlyn’s monkeys. The humid forest that carpets the monotonously flat terrain is under pressure from several sources, including a rapidly expanding human population and commercial logging. Fifty percent or more of the bonobos have vanished in the past two decades due to hunting or deforestation. Bonobos are valued as a source of protein to people in some areas of their range, and as populations grow, so too does the need for protein. Furthermore, illegally captured and exported to foreign lands for a high price, the bonobos, chimpanzees, and gorillas represent a source of cash for local people whose resources are meager at best. Zaire has designated more of its country as protected parkland than any other nation, but the region where the bonobos live is not part of that system.

  Two teams of researchers have been studying the chimps in their natural habitat since the early 1970s, one led by Randall Susman, and the other by Takayoshi Kano, of Kyoto University, Japan. When Kano surveyed the region in 1973 he estimated the chimpanzee population to be about fifty thousand. “For six or seven years following the commencement of our investigations … , the forests of Wamba were a paradise for the pygmy chimpanzees and for us researchers,” recalls Kano. “The pygmy chimpanzees, not bothered by the presence of humans, pursued a carefree life moving around the forest, and we followed them around without a care in the world.”13 Beginning in 1980, however, paradise turned into purgatory, as poachers and loggers began to plunder the forest. Instead of looking to the forest for survival, as man had done for centuries, African and non-African alike began to look upon it solely as an immediate source of monetary wealth. The fact that this wealth was clearly of limited supply only caused those wishing to take it to speed up the process.

  Sensing impending disaster, Kano and his colleagues appealed to the Zairian government to set aside a region of the forest as a reserve. The appeal was granted in 1987, which put a halt to logging plans in the Wamba forest where Kano’s research was located, and should have prevented hunting and capture. Poaching and killing continued, however, sometimes perpetrated even by government officials. Kano recalls an incident in 1988 when, in the absence of researchers at the station, regional officials entered Wamba and captured several bonobos for export. “That the formal establishment of a reserve was ineffective in checking the capture of bonobos, even by the regional government, came as a shock to me,” he recalls. “The greatest disappointment was that some of the very people who were assigned the duty of protecting the (pygmy) chimpanzees, under the new law, had initiated their capture.”14 Many local people, increasingly including immigrants to the region, remained ignorant of the law, and hunting of the bonobo for food increased rather than decreased.

  Now, two short decades since Kano’s first visit, fewer than a quarter of the original number survive, at most no more than ten thousand. In 1990, the Bonobo Protection and Conservation Fund was established in the United States and Japan, with the aim of protecting an area of six thousand square kilometers around the original Japanese research site, containing three thousand bonobos. It is a grass-roots attempt to salvage some small part of the the last ape’s former paradise. If nothing changes substantially, however, extinction of natural populations is inevitable, and the species will linger on for a while only in scattered captivity. With just eighty-five animals in zoos and primate centers around the world, that does not present a viable future. The last of the African apes to be discovered and the last to be studied scientifically in the field, the bonobo may be the first ape species to become extinct as a result of human activity.

  The bonobos Lokelema, Matata, and Bosondjo, two females and one male, arrived at the Yerkes Regional Primate Research Center toward the end of 1975. They had been wild caught in Zaire, as part of an effort by the National Academy of Sciences to aid third-world nations by fostering the development of unique indigenous resources. These bonobos ha
d left behind a familiar, lush forest and, after what was surely a nightmarish journey of change for them, now found themselves in a small cage, with dry food and surrounded by noisy, boisterous common chimps in neighboring cages. When I first saw them, they were afraid even to eat if anyone was watching.

  My goal was to study their social and communicative behavior. I also planned to spend time observing a similarly composed small group of common chimpanzees housed in an adjacent cage. It was clear that whatever I learned about these bonobos would be partially constrained by the small size of the group and their artificial surroundings. But as virtually nothing was known about bonobo behavior at the time, I felt that it was important to begin with what was available. I also believed that these recently wild-caught individuals would provide a reliable index of bonobo temperament and ability. After all, if three New Yorkers were suddenly deposited in Zaire, they might not act as they would in New York, but they would nonetheless remain human beings. If they were well fed and healthy, it would be possible to observe a wide range of human behavior, regardless of whether they knew the ways of the jungle or not.

  I was repeatedly told that I should not count on learning anything at all at Yerkes, because the bonobos were afraid of everything. Even observing was extremely difficult; if you were outdoors, they hid inside, and if you went inside, they hid outdoors.

  My first task was to get close enough to these bonobos to be able to see them. This sounds strange for a captive setting, but it was nonetheless true. I decided that I would appear as if I, too, were nervous. I hid behind a brick wall near the cage and waited until they peeked out to determine if everyone had gone. I then hesitantly began to look around with wide eyes, just like theirs, but made certain I quickly retreated with a startled expression as soon as they spotted me. They were quite amazed that a human should be afraid of them, for humans had subdued them, captured them with nets, forced them into small boxes, and poked them with sharp objects with seeming abandon. But now, one was acting afraid of them. Slowly they became a bit bolder and would sit outdoors even when I was peeking at them. They knew that if they wanted to make me go away, all they had to do was flail a hand or stomp a foot in my general direction and I would beat a hasty retreat to the safety of my hiding place. By the end of the first week I was able to be seen quietly in front of their cage, and as long as I pretended to be interested in something other than them, they would stay outdoors and go about as though I were not there.