Chimpanzee behaviour shows remarkable regional variation.
The Cultured Chimpanzee: Reflections on Cultural Primatology
- William McGrew
Thirty years ago, two young researchers, William McGrew and Caroline Tutin, visited the Mahale Mountains in western Tanzania. Until then they had been studying wild chimpanzees at Gombe, about 120 km to the north, but on their first day at Mahale they saw two chimpanzees perform a striking behaviour that was completely new to them. The two chimpanzees were sat on the ground facing one another, and were engaged in mutual grooming. At one point, each fully extended one arm overhead and clasped the other's hand. This created a sort of ‘A-frame’ postural configuration that revealed the armpit of the raised limb, which was then groomed by the other's opposite hand. The two chimpanzees were in perfect symmetry.
Returning to camp the same evening, McGrew and Tutin mentioned their discovery of the ‘grooming hand-clasp’ to their host, Junichiro Itani. But Itani was unimpressed: “Don't all chimpanzees do this?” he asked. This was a turning point for McGrew, who at that moment realized that scientists had hitherto been labouring under a simple misapprehension: that chimpanzee social life was the same everywhere.
McGrew and Tutin's pioneering report on the evidence for a ‘social custom’ in wild chimpanzees was published in 1978, but its importance was not fully recognized until later. At about the same time, fieldworkers on the other side of the continent — at Taï in Côte d'Ivoire and Bossou in Guinea — were making observations about the use of stones by West African chimpanzees. At these sites, wild chimpanzees were using stones to crack open hard-shelled nuts containing edible kernels. In contrast, chimpanzees at Gombe were known to eat the mesocarp, flower, pith, resin and cambium of the oil palm but discard its hard-shelled nut — they lacked the elementary stone technology of their West African relatives.
As increasing numbers of papers were published, the behavioural diversity of chimpanzees in the wild became clearer. McGrew's influential Chimpanzee Material Culture (Cambridge University Press, 1992) was the first book to paint a clear picture of patterns of culture. It showed that different communities of wild chimpanzees have different tools and skills, and that not all of this regional variation can be explained by the demands of the physical and biotic environments in which they live.
The Cultured Chimpanzee is a worthy follow-up, introducing a new discipline called ‘cultural primatology’. Its emergence came about as a natural extension of our expanding knowledge of cultural differences among wild chimpanzee communities. The book reviews cultural phenomena in other primate species, as well as non-primates such as fish, birds, mammals and cetaceans. According to McGrew, cultural primatology has a cross-disciplinary nature, having aspects of at least four traditional academic disciplines: anthropology, archaeology, psychology and zoology. Do non-human animals have culture? It depends on the definition. Each discipline asks different questions about culture, and uses different methods to answer them. The Cultured Chimpanzee has 196 pages of text, but contains 469 references — an indication of his dedication to synthesizing the different approaches, covering all the relevant papers about culture in non-human animals, especially chimpanzees.
When trying to sum up the book, three words spring to mind: clear, simple and deep. As McGrew confesses, he is a naturalist (as opposed to an experimentalist), but he pays attention to important issues such as imitation and teaching that have been examined in detail in the lab. He may be an empiricist (and not a theoretician), but he creates a unique framework for drawing scattered data together, thereby clarifying what is known and what is not yet known. His logic and his trains of thought are extremely clear. The text is simple to follow, even for non-English readers, and yet the messages are stimulating, heuristic and reach deep into the heart of the matter. In particular, the chapter entitled “Lessons from cultural primatology” will provide young scientists — future protagonists in the development of this new discipline — with plenty of good advice.
McGrew's Chimpanzee Material Culture is already recognized as one of primatology's classic textbooks. This 2004 follow-up should receive similarly wide attention and become another milestone in the study of the evolutionary basis of human culture. However, I would, at some future date, like to see a third book as well, written by the same author on the same topic. As McGrew mentions in the preface, The Cultured Chimpanzee was written just before his first visit to Bossou, Guinea, where a small group of 19 chimpanzees uses stones to crack nuts. As a naturalist and empiricist, coming face-to-face with this behaviour has hopefully provided McGrew with material for new and stimulating insights.
Just as McGrew concludes the book by drawing attention to conservation efforts, I would like to conclude this review by stressing the importance and urgency of protecting the chimpanzees and the forests of Africa. Chimpanzees probably once spanned most of equatorial Africa, including at least 25 countries. They probably numbered more than a million just 100 years ago. Today they occur in 22 countries, and an estimate from the World Conservation Union (IUCN) in 2003 put their numbers in Africa at between 172,700 and 299,700. This sudden decrease is linked to various human activities, such as deforestation, poaching and trading in bush-meat, as well as the transmission of diseases. For example, the Bossou community lost 5 of its 19 members to a contagious respiratory disease at the end of 2003. Similar stories are taking place all over Africa. Truly intense efforts are necessary on our part to prevent the extinction of the cultural variation among chimpanzee communities that we have so recently begun to uncover.
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Perspectives on Science (2006)