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December 2004 - Materials Science Institute - University of Oregon

December 2004 - Materials Science Institute - University of Oregon

REVIEWS Orangutan

REVIEWS Orangutan Technology HOW DID THE GREAT APES GET TO BE SO SMART? BY BARBARA SMUTS AMONG ORANGUTANS: RED APES AND THE RISE OF HUMAN CULTURE by Carel van Schaik Photographs by Perry van Duijnhoven Harvard University Press, 2004 ($29.95) In this book, Carel van Schaik, a highly regarded Dutch primatologist now at Duke University, concludes that “intelligence is ... socially constructed during development.” This won’t surprise you— until you realize that he is referring not to humans but to orangutans, the large red apes of south Asia. Van Schaik proposes that the discovery of orangutan culture can provide a resolution to a long-standing puzzle: Why are apes so smart? Perhaps the complexities of great ape social relationships selected for large brains. But orangutans challenge this “social intelligence” hypothesis: in the wild, they mostly travel about by themselves, yet they are at least as smart as chimpanzees. Van Schaik thinks that social factors are indeed pivotal in explaining orangutan intelligence, but not in the way proposed by the social intelligence hypothesis. In a beautifully written, compelling narrative that reads like a detective story, he weaves together several threads of evidence to argue that orangutan intelligence is intimately related to technological innovations that are passed down through social learning. Before hearing about the details of orangutan culture, we accompany van Schaik into the fetid, mosquito-ridden swamp forests of western Sumatra (succinctly described as human hell—but orangutan heaven). Through the large number of outstanding color photographs, we meet many of the 100 orangutans his team recognized individually. They are handsome creatures with long red hair, expressive faces and round eyes that gaze out of the photographs with keen awareness. Orangutans do something clever that other great apes don’t do: they use leaves to make rain hats and leakproof roofs over their sleeping nests. But until recently, there was scant evidence of other kinds of toolmaking. At van Schaik’s site, tools were common, and he documents in detail how the orangutans fashion tools out of twigs. They use some tools to fi sh for ants or termites, while they skillfully manipulate others to get at scrumptious seeds protected by razor-sharp hairs. At fi rst glance, these tools do not seem to refl ect advanced cognitive skills, but on closer inspection van Schaik found that each tool is carefully crafted to match the precise needs of a given situation. And like chimpanzees, orangutans sometimes make tools for later use, an apparent example of conscious planning. How do we know that such feats represent culture? The argument is complex, but in brief, orangutans’ use of tools on the islands of Sumatra and Borneo varies geographically in ways that cannot be explained by ecological or genetic differences between populations. Instead these differences are best explained by variation in sociability, as well as by the locations of geographic barriers preventing cultural diffusion between populations. In most places, intense feeding competition prevents orangutans from forming groups, and in these situations, tool use is rudimentary or absent. But swamp forests are highly productive, allowing van Schaik’s orangutans to associate a lot. As a result, youngsters spend many hours closely watching tolerant elders make and use tools. After about seven years of learning and practice, they, too, become skillful tool users. Because we already knew that material cultures vary among chimpanzee populations, why is the discovery of orangutan culture so important? Van Schaik provides three reasons: First, the existence of culture in orangutans can explain why they are so smart—something the social intelligence hypothesis ORANGUTAN mother-and-child union is one of the longest and most intense among mammals. Many foods eaten by these animals require some form of processing; youngsters must learn by observing and copying their elders. 112 SCIENTIFIC AMERICAN DECEMBER 2004 COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC. COURTESY OF HARVARD UNIVERSITY PRESS

cannot do. Second, orangutan ancestors split from the great ape lineage as long as 15 million years ago, leading van Schaik to argue that the common ancestor of all great apes (including humans) had culture at least that far back in time. If so, then the roots of human culture are much older than previously thought. Third, if the ancestor of all living great apes had the capacity for material culture, then the origins of culture must be sought in older (nonderived) traits that characterized these ancient apes. This brings us back to the question we began with: How did apes get to be so smart? Van Schaik finds the answer in a surprising place: the tops of the trees. Because ancestral apes were both largebodied and arboreal, they were much less vulnerable to predation than other mammals of their time. According to life history theory, reduced adult mortality selects for slow life histories, which in turn allow the long investment required to grow large brains and the long adult life span that makes growing them worthwhile. Apes (along with some whales and elephants) have the slowest life histories of any nonhuman mammals, and orangutans are the “slowest” apes. Infants are not weaned until they are seven, and in the wild, orangutans may live into their sixties. Thus, apes began as slow-moving, slow-growing, slow-aging animals with quick minds. Once these minds began to invent tools, van Schaik argues, apes became increasingly dependent on culture, and in a recurrent positive feedback loop, selection favored even larger brains, which improved culture, and so on. Van Schaik’s answer to the puzzle raised at the beginning, then, is that great apes started out smart because they were safe from predators and ended up even smarter because their large brains and slow life histories allowed culture to develop and fl ourish. Van Schaik’s argument has a few weaknesses—for example, the paucity of evidence for material culture in gorillas and bonobos. But, as he points out, these species have been studied intensively in only a few places, and signs of culture may yet emerge. Knowledge of great ape culture will continue to expand, however, only if these animals survive in the wild. At the end of the book, van Schaik describes how the chaos in Indonesia in the late 1990s led to widespread destruction of orangutan habitat (as well as the end of his fi eld study). Despite serious threats, van Schaik thinks the red apes may yet escape extinction, but he is much less sanguine about the survival of their cultures. Sadly, ape cultures may disappear just as they begin to provide vital new insights into human cultural evolution. Barbara Smuts is a professor in the psychology department at the University of Michigan at Ann Arbor. She is author of Sex and Friendship in Baboons (reprinted with a new preface, Harvard University Press, 1999). THE EDITORS RECOMMEND THE ANCESTOR’S TALE: A PILGRIMAGE TO THE DAWN OF EVOLUTION by Richard Dawkins. Houghton Miffl in, Boston, 2004 ($28) In this expansive book, Dawkins, the wellknown evolutionary biologist and author 114 SCIENTIFIC AMERICAN DECEMBER 2004 COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC.

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