In 1973, a 35-year-old Japanese researcher named Takayoshi Kano, the first scientist to study bonobos extensively in the wild, spent months trudging through the dank forests of what was then Zaire (formerly the Belgian Congo, now the Democratic Republic of the Congo) before he finally encountered a foraging party of ten adults. To lure them out of the trees, Kano planted a field of sugar cane deep in their habitat. Months later, he spied a bonobo group, 40 strong, feasting on the cane. "Seeing them so close, they seemed more than animals, more a reflection of ourselves, as if they were fairies of the forest," Kano told me when I visited him in 1999 at Kyoto University's Primate Research Center.
Kano expected bonobo groups to be dominated by aggressive males. Instead, females sat in the middle of the sugar cane field. They groomed each other, snacked, chatted in squeaks and grunts, and invited favored males to sit with them. On the rare occasion that an angry male charged a group of females, Kano told me, they either ignored him or chased him into the jungle. Kano's observations shocked primatologists. "Among chimpanzees, every female of whatever rank is subordinate to every male of whatever rank," says Richard Wrangham, a Harvard University primatologist.
Over time, Kano came to recognize 150 different individuals, and he noticed a close attachment between certain females and males. Kano finally concluded he was watching mothers with their sons. "I saw mothers and sons stay together and realized that mothers were the core of bonobo society, holding the group together," he said.
One of the reasons to study primates is to better understand our own evolutionary history. Bonobos and chimps are our closest living links to the six million-year-old ancestor from which both they and we descended. As primatologist Frans de Waal points out, Kano's work "was a major revelation, because it proved the chimpanzee model was not the only one to point to our origins, that another primate akin to us had developed a social structure mirroring our own." When Kano's findings were publicized, in the 1970s, the animals' friendly family relations, peaceable males, powerful females, high I.Q.s and energetic sex lives made the idea of sharing an evolutionary lineage with bonobos appealing.
Wild bonobos live within several hundred thousand acres of dense swampy equatorial forest bounded by the Congo and Kasai rivers in the Democratic Republic of the Congo (DRC). Only 23 percent of their historic range remains undisturbed by logging, mining or war. From 1996 to 2003, the country suffered back-to-back civil wars, and foreign researchers and conservationists stayed out of bonobo territory, which saw some of the fiercest fighting. The New York-based International Rescue Committee estimates that the strife constituted the world's deadliest conflict since World War II, with five other African nations and numerous Congolese political factions fighting for territory and control of the DRC's immense natural resources—copper, uranium, petroleum, diamonds, gold and coltan, an ore used in electronics. Some four million people have been killed. The conflict officially ended in April 2003, with the ratification of a peace treaty between the DRC's young president, Joseph Kabila, who seized power after his father, Laurent, was assassinated in 2001, and several rebel groups. An uneasy truce has held since then, which has been tested during the run-up to a presidential election scheduled for October 29.
To observe bonobos in the wild, I fly to Mbandaka, capital of the DRC's Equateur Province, a destitute-looking city of more than 100,000 people by the Congo River. Civil war has left the city without water or electricity; mass graves of civilians executed by soldiers have been found on the city's outskirts. I embark with three foreign and seven Congolese conservation workers on a trip upriver by motorized pirogues, canoes hacked from tree trunks. We start on the Congo River, one of the world's longest at 2,900 miles from source to sea. Researchers say this geographic barrier, up to ten miles wide, has kept chimpanzees in jungles on the Congo River's north side and bonobos on the south, which allowed them to evolve into separate species.
As darkness drops a velvet curtain along the great waterway, we enter the Maringa tributary, which cuts deep into the heart of the Congo Basin. Twisting and turning like a giant snake, the Congo River is guarded on both banks by what Joseph Conrad, writing about it in Heart of Darkness, called a "great wall of vegetation, an exuberant and entangled mass of trunks, branches, leaves, boughs, festoons motionless in the moonlight." By day fish-eagles, herons, kingfishers and hornbills perch by the fast-flowing muddy water; local people pole canoes from their straw huts to market. At night the riverbanks echo with the urgent thump of unseen drums and raucous singing.
On our second morning, we pull in at Basankusu, a riverside town with a military base, where I show my permit to travel farther up the river. This area was a center of opposition to President Kabila, and government functionaries treat strangers with suspicion. Fierce battles between Kabila's forces and those of Jean-Pierre Bemba, who controlled the north, were waged here, and sunken barges still lie rusting in the shallows. According to the relief agency Doctors Without Borders, 10 percent of Basankusu's population perished over a 12-month period beginning in 2000. There is a brooding menace here, and I sense that a wrong word or movement could spark an explosion of violence. As our pirogue prepares to leave, a hundred soldiers led by shamans clad in leafy headdresses and skirts charge toward the river chanting war cries. "It's their morning exercise," a local man assures me.
All along the river I see grim evidence of the fighting. Much of the DRC's prewar export income came from rubber, timber and coffee plantations along the Maringa, but the riverside buildings are now deserted and crumbling, mangled by artillery fire and pockmarked by bullets. "The military looted everything along the river, even light sockets, and it'll take a long time to return to normal," says Michael Hurley, the leader of this expedition and executive director of Bonobo Conservation Initiative (BCI), a Washington, D.C.-based nonprofit organization.
By the fifth day, the river has narrowed to 20 yards, and the riverside villages have all but disappeared. Trees tower over us, and we slow to dog-paddle speed. At night a ghostly mist settles on the river. We tie the pirogues to reeds and camp on the boats, then leave at dawn just as the mist is rising.