The Unexpected Adaptability of Chimps to the Human World
As conservationists scramble to protect decimated ape populations, chimps are adjusting to new surroundings in surprising ways.
At twilight, the great apes had us surrounded. Straight ahead, a silverback gorilla turned his resplendent back, hair bristling, to avoid our gaze. On our right, female chimpanzees poked sticks into a faux termite mound.
On this gray evening in August, hundreds of great-ape scholars squeezed between the glassed-in enclosures of the Lincoln Park Zoo’s Regenstein Center for African Apes. They were in Chicago for an international conference called Chimpanzees in Context. As they streamed past, the chimps paid little attention. The mature females glanced over, adjusted their wands, and continued trolling for treats.
This “fishing” behavior is an example of tool-making and tool use documented by Jane Goodall in the forests of East Africa. More than a half-century ago, Goodall’s field observations upended the notion that chimpanzees don’t make or use tools in the wild. Ever since, great-ape scholarship has been shaped, in part, by a raucous debate over whether more subtle differences between chimps and humans were matters of degree or kind. New research turned less on what makes chimps distinct from humans and more on the essence of chimps themselves.
The wan, pert, reed-thin woman, pausing wide-eyed in the Regenstein Center’s entryway was the 82-year-old conservationist herself. “What a zoo!” Goodall exclaimed, referring not to the gorillas and chimpanzees, but the mob of hairless, gawky bipeds (outliers, in these respects, among our genetic kin) yipping past one another towards an open bar. When Goodall began her research in the 1960s, all of the world’s experts on chimpanzees might have fit around a small coffee table. Now, they numbered in the hundreds, assembled for the largest gathering of chimp researchers since an inaugural conference of this kind back in 1986.
The apes may have had us surrounded, but we had them far outnumbered—which is, of course, the main rub in their existence.
In the scrum, the field’s best-known trailblazers jostled up against clusters of younger scholars. To an outsider, it looked like a generational handoff was under way. Earlier in the day, in reports about current research offered in a meeting room nearby, the next generation appeared to have left that timeworn argument about human/ape differences behind. They were fixed more intently on comparisons between non-human species, great-ape or otherwise, such as chimps versus bonobos, or chimps versus dolphins.
In the process, these young researchers have discovered evidence of remarkable behavior changes as chimpanzees come to live in ever-closer, and often fraught, proximity to humans. Their work tells a companion story to regular and worrisome predictions of great ape extinction. Up against swiftly changing conditions, chimps are managing to adapt in surprising ways.
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Gatherings of great-ape specialists border on the funereal. Four of six great-ape species (including both species of orangutans in Indonesia) are critically endangered, just one step away from extinction. The non-captive cousins of the two great-ape species in the center, Western Lowland gorillas and chimpanzees, are endangered, two steps from extinction. In recent decades, chimpanzee populations in Africa, estimated at 150,000 to 200,000, have been decimated because of expansion of palm-oil plantations (an industrialized form of agriculture), logging, hunting, climate change, and disease.
“We’re surrounded by doom and gloom,” Goodall said. But alongside these dominant trends were strands of a more hopeful counter-narrative, which she was eager to highlight. Making a beeline to an oversize electronic monitor smack dab in the middle of the hall, Goodall was joined by Tetsuro Matsuzawa, a primatologist from Japan best known for breakthrough research on instantaneous memory, and extraordinary spatial intelligence, among chimps.
Goodall and Matsuzawa met back at the inaugural Chimpanzees in Context conference, 30 years ago, at a time when great ape scholarship was marked by a sharp divide between experimenters in the laboratory and chimpanzee/bonobo researchers in African forests. Matsuzawa was one of the few scientists of his generation doing research in both settings, so he and Goodall helped bridge a troubled divide. Over the decades, they’ve grown quite close.
(Lisa Miller / Lincoln Park Zoo)
At the monitor, Lilian Pintea, the chief of conservation at Goodall’s institute in Washington, D.C., flashed a global overview of African landscape from 2010 to 2014. He pointed out the red shading, which indicated vast swaths where habitat had been lost or was threatened. He also showed back-to-back images from two villages adjacent to Goodall’s study site in Tanzania, revealing robust reforestation.
This progress was due, in part, to a program that placed Android mobile phones and Tablets in the hands of rangers and local residents. Now, they could capture evidence of incursions, snares, and illegal logging, upload it quickly, and allow local authorities to respond swiftly enough to make a difference.
“Look at what happens when we work with people,” Goodall said.
It wasn’t only fresh evidence of success in getting humans to respond more effectively to threats to the existence of chimpanzees that excited her. There were also accumulating reports at the conference about the adaptive social intelligence of chimpanzees.
In a meeting hall near the ape house, a young Japanese researcher named Shinya Yamamoto rolled a bit of video from an ongoing study. Like Matsuzawa, Yamamoto had worked with captive chimps in Japan, and also observed both bonobos and chimpanzees in Africa. The clip showed a pair of dominant males cross a narrow dirt road, scanning it in both directions. They station themselves on the opposite side of the road and stand guard as a mother with an infant on her back, and seven other members of their community, scoot by.
In similar footage, available from an earlier study, adult chimpanzees behave much like school crossing guards. This is an example of group coordination, vigilance, waiting and escorting, Yamamoto explained. Since bonobos haven’t been observed escorting and guarding in this way, it could be distinctly chimpanzee behavior. Chimps are hunters and meat eaters, unlike other great apes and more like humans, so perhaps the quality of coordination needed in organizing a hunt prepares chimpanzees for escorting others in this way to avoid danger on the road.
Videos of other researchers’ work flashed onscreen. From savanna in Senegal there’s evidence of tool use of a different kind, akin to making weapons. Jill Pruetz, a biological anthropologist from Iowa State University, has documented the ways adult female chimps sharpen the ends of sticks with their teeth and use them to hunt small primates called galagos. “To find chimpanzees spearing bush babies—that’s outside of any expectation!” Matsuzawa exclaimed.
Goodall also lit up about this study, and others that emphasized varied examples of adaptive behavior seen in chimpanzees. She was especially intrigued by current work on chimps now living in hot, dry, flat, less-forested landscape. This is terrain more like landscape once occupied by our human ancestors than traditional chimpanzee habitat.
There were plenty of surprising observations—sightings of chimps lounging in ponds to cool off (when they were supposed to be water phobic), picking crops in nearby human communities after sunset (though they were supposed to be afraid of the dark), and hanging out in caves, when nobody elsewhere on the continent had reported anything like it before.
“In Mali, they’re cooling off in caves,” Goodall said. “In Uganda, they learned to raid sugar cane at night. These chimps are living right at the edge of where it’s possible for them to exist.”
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By the middle of the evening, the female chimpanzees left off fishing for food and began gathering straw to build sleeping nests for the night. Though nest-building is a foundational skill, a recent broad survey of captive chimps held in labs, private homes, zoos, and sanctuaries found that only 55 percent build them.
New studies presented in the meeting hall also confirmed that female adults, like the chimpanzees we’d seen fishing, have more patience for tool making than males: They use leaves as sponges for water, for example, while males tend to dispose of them as penis wipes; they learning to crack nuts with stones and catch termites more quickly. This poses something of a cross-species mystery. Among humans, scientists think that boys engage more in object play than girls, so what accounts for the difference between us and chimps?
Or for the differences between chimps and bonobos, which lie closer to humans in evolutionary terms? Chimps use tools in foraging for food while bonobos don’t. As Richard Wrangham, a well-known biological anthropologist from Harvard University in attendance, put it: “Are we talking about the loss of a capacity rather than a gain?”
Chimpanzees and humans share at least three other characteristics missing in bonobos: We hunt, eat meat, and are known to intentionally kill creatures of our own kind. No other great apes do any of these things.
Fresh reports of rising numbers of murders from Gombe, with alpha males killing infants and adult females murdering young of other mothers left researchers at the conference shocked and intrigued. “That’s one of the times I think: Boy I’d like to jump in and study that myself!” Goodall said.
As the evening wore down, the apes settled in for the night. Glancing up past the faux trees in the faux forest you could see flashes of black, the lurch of a stray foot or elbow, and the glint of an eye whenever one of the chimps glanced over to see if the strange-looking creatures, still discussing them, were swirling around down below.
Communication among chimpanzees invokes a complicated interplay of gestures, facial expression and sound, explained Catherine Hobaiter, a psychologist from the University of St. Andrews. Among chimps and bonobos, she noted, there are more than 60 different ways to communicate two things: “Please groom me” or “Stop that.”
A senior scientist, William McGrew, mentioned that chimps had such a rich array of ways to greet one another, but he speculated that there was nothing like it for leave-taking. Why, he wondered, don’t chimpanzees say goodbye?
By 9 p.m., the spigot for hazelnut-and-fig beer, dubbed Chimp Off the Old Block, ran dry. Groups of scientists reversed direction, fusing for a last exchange before splitting apart, a visual reminder of the fusion/fission pattern of chimpanzee culture.
Goodall thought the next global meeting should land right at the intersection many of the younger researchers had begun to explore—in the places where humans and chimps sometimes collide, and often co-exist, in unexpected ways. “The questions that fascinate me now are questions of cultural variation,” Goodall said. “The extent to which chimps adapt to different environments and adapt to living next to people.”
She seemed to be trying to work out what additional work she could do on their behalf, at the age of 82—and to absorb this news about what they’d proved capable of doing themselves.
The last time I caught sight of her in the ape house, Goodall was bouncing slightly on the balls of her feet and peering through thickened glass into the rafters of the chimp enclosure. Then, she pivoted without another word—no goodbye—and jetted through the heavy glass doors down dimly lit concrete pathways right out of the zoo.