Kanzi: The Ape at the Brink of the Human Mind (17 page)

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 the 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.