Led by five trackers from the Mongandu tribe, I tread through a remote rain forest in the Democratic Republic of the Congo, on the trail of the bonobo, one of the world's most astonishing creatures. Along with the chimpanzee, it's our closest relative, with whom we share almost 99 percent of our genes. The last of the great apes to be discovered, it could be the first to become extinct in the wild: in the past few decades, bonobo habitat has been overrun by soldiers, and the apes have been slaughtered for food. Most estimates put the number of bonobos left in the wild at less than 20,000.
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As the narrow trail plunges into a gloomy, rain-soaked tunnel through tall trees, Leonard, the head tracker, picks up a fallen leaf and brings it to his nose. "Bonobo urine," he murmurs. High above I see a large, dark, hairy creature propped between the trunk and bough of a sturdy hardwood. "The alpha male," Leonard whispers. "He's sleeping. Keep quiet, because it means there are bonobos all around us."
We creep toward the tree and sit beneath it. I try to ignore the fiery bites of ants crawling over my arms and legs as we wait for the bonobos to awaken. They are known to be gregarious, exceptionally intelligent primates, and the only apes whose society is said to be matriarchal...and orgiastic: they have sexual interactions several times a day and with a variety of partners. While chimpanzees and gorillas often settle disputes by fierce, sometimes deadly fighting, bonobos commonly make peace by engaging in feverish orgies in which males have intercourse with females and other males, and females with other females. No other great apes—a group that includes eastern gorillas, western gorillas, Bornean orangutans, Sumatran orangutans, chimps and, according to modern taxonomists, human beings—indulge themselves with such abandon.
But when these bonobos awaken, their signature behavior is nowhere in evidence. Instead, dung splatters the forest floor, flung at us by the alpha male. "He's angry we're here," Leonard says softly. The male screams a warning to the other bonobos, and they respond with shrill cries. Through binoculars, I see many dark eyes peering down at me. A youngster shakes his fist at us. Moments later, the bonobos are gone, swinging and leaping from branch to branch, led across the rain forest canopy by the big male.
Because so much of what's known about these animals has been based on observing them in captivity or in other unnatural settings, even my first encounter with them in the wild was revelatory. The alpha male's bellicose display was just the first of several signs I would see over the next ten days that not all is peace and love in Bonoboland. Maybe it shouldn't be surprising, but this close relative of ours turns out to be far more complicated than people realized.
It was at Germany's Frankfurt Zoo some years ago that I first got hooked on bonobos. One of their nicknames is pygmy chimp, and I had expected to see a smaller version of the chimpanzee, with the same swagger and strut in the males and timorous fealty in the females. Bonobos are smaller than chimps, all right—a male weighs about 85 to 95 pounds and a female, 65 to 85 pounds; a male chimpanzee can weigh as much as 135 pounds. But the male bonobos I saw in the zoo, unlike the chimps, did not try to dominate the females. Both males and females strode about the enclosure picking up fruit and mingling with their friends. They looked strangely human with their upright, bipedal gait; long, slim arms and legs; slender neck; and a body whose proportions resemble ours more than they do a chimp's. More than anything, they reminded me of models I'd seen of Australopithecus afarensis, the "ape man" who walked the African savanna three million years ago.
In 1920, pioneer primatologist Robert Yerkes of Yale University named a bright young primate captured in the wild "Prince Chim." Comparing him with other chimpanzees he was studying, Yerkes said Prince Chim was an "intellectual genius." Only in 1929 did scientists realize that bonobos are a distinct species (Pan paniscus) and not just undersized chimps (Pan troglodytes), and we now know from photographs that Prince Chim was actually a bonobo.
The bonobo's life history is typical for a great ape. A bonobo weighs about three pounds at birth and is carried around by its mother for the first few years. She protects the youngster and shares her nest with it for the first five or six years. Females give birth for the first time at age 13 to 15; males and females reach full size at about age 16. They can live up to about 60 years.
Yerkes' observation of superior intelligence has held up over the years, at least in captive animals. Some primatologists are convinced that bonobos can learn to communicate with us on our own terms.
As I stood near the bonobo enclosure, an adolescent female named Ulindi reached through the bars and began to groom me, her long fingers tenderly searching through my hair for bugs. Satisfied I was clean, she offered her back for me to groom. After I did so (she, too, was bug-free), I left to pay my respects to the group's matriarch. Ulindi's eyes burned with indignation, but minutes later she drew me back with a sweet gaze. She looked at me with what seemed affection—and suddenly tossed into my face a pile of wood shavings she'd been hiding behind her back. She then flounced away.