Male chimpanzees modulate their voices so that they sound alike, chimps at  different sites have different dialects

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.