Aping Culture

Chimpanzees speak in dialects, invent odd grooming styles, and drum better than most kids in marching bands. So what's left to separate them from us?

By Meredith F. Small, Cleo Sullivan|Monday, May 01, 2000
In the summer of 1960, a young English woman stood on the shores of Lake Tanganyika looking into the hills of Gombe Stream Reserve with her mother. From the shore, Gombe seems impossible to negotiate: Steep, tree-covered ridges and their corresponding ravines rise from the beach as if a giant child had reached down with spread fingers and scraped the landscape upward. The pant-hoot calls of chimpanzees--husky puffs of noise that rise quickly into wild screams--echo across the ravines and taunt any visitor to follow the apes across the undulating terrain.

The young woman spent the first months trying to catch up with her subjects, scrambling up cliffs, grabbing onto roots, and then standing perfectly still so as not to scare them away. The only way the chimps would tolerate her presence, she eventually found, was if she lured them close with bananas. Thus began a decades-long effort to follow around groups of chimpanzees to figure out what they can tell us about ourselves.

Her name, of course, was Jane Goodall, and in the years that followed she would become an icon of both sober science and exotic adventure. The willowy figure dressed in green fatigues, the limp blonde hair drawn back in a ponytail, the quiet British voice narrating innumerable National Geographic specials—these images and sounds are inextricably bound to the public’s understanding of chimp behavior. Before Goodall’s work, chimpanzees were known mostly from studies on animals that had been captured and imported to indoor and outdoor laboratories. Although psychobiologists like Robert Yerkes knew that chimps were smart, no one was sure how they used those smarts in the wild.

“When I went to Gombe, nothing was known,” Goodall said recently, “Chimps weren’t allowed to have personalities—no names, no reasoning ability, no emotions. Until one recognized the individuals, you couldn’t work out the social structure, nor could you make any sense of the communication. It was so confusing.” Goodall’s work changed all that. Her detailed daily records of individual chimpanzees—maintained these days by other primatologists and field assistants—resulted in the first chimp personality portraits, as well as startling discoveries of chimpanzee tool use, hunting practices, and even murder.

That was just the beginning. For the past four decades, an army of researchers from Europe, Japan, and the United States has observed chimpanzees at more than 40 sites. In 1966 Toshisada Nishida began a study in the Mahale Mountains, 90 miles south of Gombe, and went on to identify the basic social structure of chimpanzee communities. In the 1970s, researchers discovered that chimps living in Guinea and Ivory Coast, on the far western edge of their species’s range, hunted and used tools differently from their eastern cousins. A decade later, Richard Wrangham, working in both Gombe and the Kibale National Park in Uganda, showed that chimps can act much the same even when they live in different habitats and have different diets. Takayoshi Kano and others, meanwhile, have cast a new light on chimpanzee behavior through studies of the bonobo, the chimpanzee’s more peaceable, more egalitarian cousin.


THICKER THAN BLOOD

Male chimps tend to be a tight bunch. They sit close and groom each other, hunt together, and close ranks periodically to patrol their boundaries silently. Sometimes they even sneak outside their territory to beat up or kill males from neighboring groups. The compelling force behind all this male bonding, primatologists concluded, must be kinship. After all, males always stay in the group where they’re born, while females leave when they are sexually mature.

Now, thanks to molecular genetics, we know otherwise. Over the past nine years, in Uganda’s Kibale National Park, researchers from Harvard University and the University of Michigan have scavenged hair left by nesting and self-grooming chimpanzees. Embedded in those samples are cells that provide a dna blueprint of each chimp. When the researchers compared the chimps’ kinship to their behavior, they found that males who sit together and groom each other are not closely related. More significant still: Those who hunt and patrol borders together aren’t closely related either.

Kinship doesn’t underlie male cooperation, in other words.  Chimpanzees get to know each other and keep track of the political intrigue that goes with making, breaking, and manipulating relationships. Although kinship is important, chimps often also rely on the fragile ties of friendship.

They sound more like people every day. —M.F.S.


Last summer, researchers from seven long-term field sites combined their results in a landmark report in the journal Nature. Led by primatologist Andrew Whiten of the University of St. Andrews in Scotland, they listed 39 chimpanzee behaviors that go beyond mere survival strategies. More important, those behaviors vary from group to group: In some areas, for instance, chimpanzees dip for ants with a long stick, swipe the ants into a ball, and then flick the ball into their mouths. At other sites they use a short stick and slurp the ants with their tongues. Some chimpanzees clip the edges of leaves as a display; others use the leaves as napkins. Perusing the total list is a bit like thumbing through a Fodor’s travel guide. And that is exactly the point. Chimpanzees, Whiten and his colleagues concluded, have culture.


Critics wasted no time in raising objections. Culture means more than just a set of learned behaviors that vary from place to place, some argued; culture means history and tradition, art, philosophy, and religion—the last barrier, together with language, that separates humans from other species. Others voiced more subtle concerns: “Are we measuring what we really think we are measuring?” anthropologist John Mitani of the University of Michigan wonders. “Just because it’s different at two different places—is it culture?”

The debate boils down to semantics as much as science, and it largely misses the point. The fact that different chimps learn different ways to act hardly makes them human—it may not even make them cultural. But it does raise a far more intriguing question, one that has long seemed unanswerable: What can those learned behaviors tell us about the origins and purpose of human culture?

The Bossou Nature Reserve in the Republic of Guinea pops up from the West African plain like a green thumb. It looks almost out of place—a leafy oasis in a sea of humanity, a spot of nature amid peasant villages and irrigated rice and manioc farms. But this forest was here long before the people began cutting down the trees, planting crops, and corralling the resident chimps toward their last stand. Today, a village sits at the base of the reserve, and villagers, looking up, can see the animals bounce among the trees. Their backyard is essentially a natural exhibit of chimpanzees.

And what curious chimps they are. As one walks up the hillside, out of the village and into the forest, the hubbub of talking, laughing, and shouting people fades away, and the air begins to ring with hollow knocks and smacks. It sounds as if workers in a factory are beating some product into shape, but a closer look shows that it’s a group of chimpanzees sitting together cracking nuts. An old female grabs a heavy stone and makes sure it’s flat, then wedges another stone underneath it to keep it from rocking. She places an oil palm nut on top, into a spot worn smooth from hours of smashing. Holding a lighter stone in her hand, she raises it high above her head and slams it down, crushing the nut to pieces. She then delicately picks out the nut meats and chews them contemplatively, clearly enjoying her fatty snack.

What makes this scene so interesting is not just that chimps are smart enough to figure out how to crack hard-shelled nuts, but that their method of doing so is specific to West Africa. In the Mahale Mountains in East Africa, chimpanzees walk right by those nuts, oblivious to their nutritious meats. Moreover, nut-cracking is clearly a learned behavior, since it takes years to master. When young chimps at Bossou try their hand at it, primatologist Tetsuro Matsuzawa has found, the nuts keep slipping off the flat stone, or the young chimps can’t hit them, or they strike at a bad angle and the nut goes whizzing through the forest like an errant bullet. It takes years of watching how it’s done, and lots of practice, before the youngsters get anywhere.

Nut-cracking has all the elements of a cultural behavior: It only occurs at some sites and is passed down by learning and imitation. But other presumed cultural differences are more subtle. For example, John Mitani has found that male chimpanzees’ pant-hoots crescendo differently depending on where they live. At one site, the calls sound like a train slowly leaving the station—chug-ah, chug-ah, chug-ah—gradually accelerating toward a scream. Elsewhere the buildup is faster, higher-pitched, and more frantic. More intriguing still, males at each site seem to modulate their voices so that their calls sound alike. By doing so, they are presumably announcing their joint presence and confirming that they belong to the same group.


SPLITTING HAIRS

Chimps have grooming subcultures, each with a distinctive style.

One of the best examples of chimp culture can be seen in the Mahale Mountains of Tanzania and in Gombe, 90 miles to the north. Though the two areas lie on the same side of Lake Tanganyika, the chimpanzees have more elaborate grooming habits in Mahale. In Gombe, when a male chimp lumbers up to a friend and sprawls out on the ground, the friend will usually groom him by gently passing a hand through the fur on his back, chest, face, or leg. In Mahale, chimps prefer to face each other, lock hands, and raise their arms in a mutual salute. The same style is seen at several other sites across Africa, and in captive populations, but not in Gombe. Is the Mahale style simply the most efficient way to groom an armpit? Or is it the chimpanzee version of a secret handshake?

Anthropologist William McGrew has studied the Mahale chimps, and several other groups, for 20 years. He not only believes that their grooming is cultural, but also thinks there are grooming subcultures as well. Recently, when McGrew showed his students at Miami University in Ohio some old photographs of chimps grooming, he noticed something: One group at Mahale groomed the usual way while another group at the same site had a slightly different technique. “This is like the difference between the three-fingered salute by the Boy Scouts and the two-fingered salute by the Cub Scouts,” McGrew says. “We are really dealing with nuances. But they’re there.”

McGrew hopes that such studies will help motivate people to protect chimpanzees in the wild. “There are chimpanzee cultures that are winking out as we speak,” he says. “If we need any new impetus to keep us pushing, that’s it: We are not just saving gene pools and we’re not just saving individuals. We are saving something that approximates culture.” But Jane Goodall, for one, is far less sanguine. “It’s fine to work for the rights of chimps, but humans have rights that don’t protect them,” she says. “Look what is happening in Africa, look at the genocide. The Hutu won’t deny that the Tutsi are cultural and have rational thoughts and emotions, and vice-versa, and they still kill each other.” —M.F.S.


Mitani tentatively calls these different pant-hoots “dialects,” but he acknowledges that what he hears may be a product of differences in body size, genes, or habitat. “It wouldn’t be fair to compare the calls produced by West African chimps, who are larger and have deeper voices, with small East African chimps,” he explains. Yet the calls don’t seem to be tailored to their habitats either. In the Mahale Mountains, low-pitched calls would carry farthest, yet the chimps have relatively high voices; in Gombe’s open woodland, high-pitched calls would travel best, but the chimps have low voices.

Even if the differences in calls are learned, some linguists might question Mitani’s terms. When he says that chimpanzees have dialects, he means that different groups make different sounds even though their members can intermingle. But when people are said to speak a dialect, the term means more than just distinctive sounds. “Dialects are two versions of a language that are still mutually comprehensible,” says Robbins Burling, a linguist at the University of Michigan. Or as Massachusetts Institute of Technology psychologist Steven Pinker puts it: “The standard definition is that a language is a dialect with an army and a navy.” Pinker is quick to add that Mitani’s use of the term is “innocuous.” But even the most open-minded linguist or primatologist wouldn’t say that chimpanzees speak a language.

Does it matter? Do chimpanzees have to be so much like humans to have culture? The answer depends on your definition of culture—and a dozen anthropologists will give you a dozen different definitions. If, as some say, culture is any learned behavior that is shared by a collective, chimpanzees easily make the grade. As Barbara Miller, a cultural anthropologist at the George Washington University, puts it: “If we take a broader approach to culture, as I do, and include foraging behavior and sex, much of what chimpanzees do would be considered culture.” But other anthropologists are more discriminating. Culture, they argue, is what people say and think, not what they do; it deals with symbols and meaning rather than behavior. Practicing a religion is cultural, according to this definition; plowing a field is not.

If that’s the case, chimpanzees will never join the culture club. “None of us,” anthropologist William McGrew admits, “knows what significance chimpanzees attach to some of the weird and wonderful things they do.” Still, Whiten and his colleagues have shown that chimps can imitate complex behaviors step by step (though they never teach one another deliberately). The longer primatologists study chimpanzees and the more their findings are compared, the longer the list of unique learned behaviors grows.

Taken together, those traits may open a window on early human behavior as well. For example, according to a recent survey of five long-term chimp studies, the most sociable chimps tend to be best at using tools (captive chimps, by the same token, are better with tools than wild chimps). That pattern may help explain how early hominids, despite their smaller brains, gradually developed complex cultures. After all, fossil evidence shows that early humans only began to use tools after their canines (which they may have used to fight one another) began to shrink.

To get a less theoretical sense of how chimp culture and human culture are related, you might try standing quietly in Kibale National Park and listening hard. Chances are, instead of the monotonous sound of nut-cracking, you’ll hear something more complex: a hollow knocking, a double-time thump-thumping that echoes through the trees.

Chimpanzees, you’ll find, can drum.

The trees at Kibale and other sites often have huge buttresses that rise several yards from the leafy litter to the canopy overhead. By slapping at the buttresses with their hands, chimps can create rhythmic patterns that can carry for more than a mile. Adam Clark Arcadi, an anthropologist at Cornell University, has spent four years collecting these sounds. To do so, he and his research assistants simply stand in the forest and point a directional microphone toward a drummer. Later, back in his lab, Arcadi runs the recording through a sophisticated computer program that creates images of the sound. From that image he can measure differences in rhythm and pitch among drummers.

Chimp drumming is a male thing, as far as we know. Males do it throughout the day, most often when on the move, with each bout lasting anywhere from a few seconds to almost half a minute. Like jazz drummers knocking out a riff, each chimp seems to have a signature beat. “There are differences in the speed at which they drum, and in slaps that come in pairs—ba-dump-ba-dump-ba-dump—versus single beats—dump-dump-dump,” Arcadi explained one day, hitting his desk to demonstrate. Like people, chimps can be righties or lefties, and they probably favor their better hand when drumming. When Arcadi played some of his drumming tapes, spliced together into a continuous loop, it sounded like elementary jazz.

All chimpanzees presumably drum to communicate with one another (though no one knows what they’re communicating). But Arcadi has found that males at Kibale often drum without calling, whereas males in Taï National Park usually pant-hoot as well. One could say, therefore, that chimpanzee drumming is multicultural. Maybe there’s even a link between what chimps pound out in the forest and the sounds that their human counterparts make on a Saturday night.

To deepen our concept of their culture, primatologists will have to learn more about chimps’ interpersonal relationships. Do chimps from various sites treat each other differently? Are the customs and manners of East African chimps as different from those of West African chimps as, say, Samoans’ are from Icelanders’? Are males more repressive toward females at one site and more easygoing at another, echoing the variety of human male-female relationships across the globe? In the words of primatologist Frans B.M. de Waal, who observes chimpanzee social behavior at the Yerkes Primate Field Station in Atlanta: “Who fishes for ants and who doesn’t, or who cracks nuts and who doesn’t—that’s the easy thing to see. But the social dynamics, that’s much harder to put your finger on.”

Who knows what’s left to discover? “I now regard chimpanzees as a very big mystery,” says anthropologist Vernon Reynolds, who works in Uganda’s Budongo Forest. “The more we find out, the less we understand.” McGrew agrees: “I have been struck by the richness of chimpanzee nature. There is always a new twist on an old theme that causes you to smile and revise yet another set of conclusions. There is such a wonderful wealth of stuff here.”

Late in the fall, Jane Goodall took some time away from her most recent book tour—and plans for yet another African safari—to talk about the chimp culture studies. The new findings hardly come as a surprise, she said. “I wrote an article in 1973 saying that the big challenge now, the most important thing, is to learn about cultural variation.” As for the definition of culture, she still uses the one she has always used: “It’s simple. You just have to prove that the behavior is passed down through observational learning rather than instinct.”

Nevertheless, the studies that Goodall set in motion so long ago are quickly carrying us beyond such simple answers. Perhaps chimpanzees are more guided by cultural rules in their day-to-day interactions than we realize. Or perhaps some of the activities that we consider patently cultural—in humans as well as chimps—are really shaped by the environment.

“I don’t think everything humans do is cultural,” says cultural anthropologist Lee Cronk of Rutgers University. In one Kenyan tribe, for instance, tradition dictates that boys are more desirable than girls, yet parents consistently treat girls better. The reason, Cronk says, is that girls in that area are more likely than boys to give their parents grandchildren. Culture may urge one behavior, but biology urges another—and the latter wins out.

“Culture isn’t what we do,” Cronk concludes, “it’s the information that we share that tells us what’s appropriate to do. It’s not the act of baking a cake; it’s the recipe.” The trick is determining when we’re improvising and when we’re cooking by the book. What part of marriage, for instance, is biological and what part cultural? “Culture is complicated when it comes to humans,” Cronk admits. “But with chimps it’s relatively simple. You can get your mind around it. It allows you to see very clearly that they behave in many ways with no cultural input. When people see that, it’s easier to convince them that, yeah, culture isn’t the only thing that is influencing human behavior.”

Goodall’s definition of culture, cut-and-dried as it sounds, still smudges such distinctions. For decades she has been the preeminent authority on chimpanzees, and her major work, The Chimpanzees of Gombe, has been a kind of bible to primatologists. Published in 1986, its 673 pages once seemed to contain everything one could ever want to know about chimps. These days, though, when you get it down from the bookshelf, you notice that the pages have yellowed, and that a damp, musty library smell rises from them. The Chimpanzees of Gombe no longer seems a sacred text, but a piece of history.

And soon, it may be a relic.

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