7.3 Acquiring Resources and Transmitting Knowledge: Got Culture?
FIGURE 7.6Chimpanzee Tool Use When “fishing” for termites (which are highly nutritious), a chimpanzee selects a branch or twig thin enough to pass through the holes of a termite nest, then removes all extra branches and leaves and inserts the twig into the nest. Simple and disposable, even primitive, tools like this might have been used by our ancestors long before the appearance of stone tools some 3.3 mya.
Primates and humans acquire food in vastly different ways. While primates can acquire food using primarily their bodies, humans depend on technology—material culture—to acquire food. But this distinction does not mean that primates have no material culture.
In the 1960s, Jane Goodall became the first to question that assumption when she observed adult chimps poking twigs into a termite hill, withdrawing them, and eating the termites that clung to the twigs (Figure 7.6). Goodall realized that one fundamental assumption about what it means to be human—namely, that material culture (and culture in general) is exclusive to human beings—seemed incorrect. Other scientists then realized that living chimpanzees’ tool use may be the best model for understanding our prehuman ancestors’ earliest cultures and the origins of tool use in hominins (among the topics of chapter 10).
7.5
Primate Predation in the Taï Forest
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RAPTORS
Crowned Eagle Found throughout Africa south of the Sahara Desert, the crowned eagle (Stephanoaetus corontus) is among the most successful raptors in the world. This carnivore preys on a range of animals, including primates.
Eagles, hawks, buzzards, falcons, and owls are predators known collectively as raptors, or birds of prey. Anthropologists, field ecologists, and other scientists have long been skeptical that primates could be preyed upon by these predators, owing to doubts about the birds being able to lift something as heavy as some primates off the ground. Extensive field studies have revealed, however, that small primates worldwide—indeed, most primates—are routinely and efficiently killed by raptors.
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PRIMATES
Campbell’s Guenon The Campbell’s guenon (Cercopithecus campbelli) has a distinctive yellow band across the brow and blue shading around the eyes. It is among the most common monkeys in West Africa. Although adapted to the shelter of the dark understory of the Taï Forest, the Campbell’s guenon is choice prey for crowned eagles.
Which primates are the crowned eagles preying upon? Despite the fast movement and well-developed vocalized warnings of the Diana monkey and the inconspicuous nature of the Campbell’s guenon, both species commonly fall victim to crowned eagle predation. Sooty mangabeys (Cercocebus atys), the largest cercopithecoid monkeys in the Taï Forest, are also among the most common victims. Prior to her study, Susanne Shultz predicted that the sooty mangabeys’ large body size and group-oriented social structure limited predation by even these highly aggressive birds. Her study revealed instead that raptors are fully able to prey upon primates weighing more than 11 kg (24.25 lb) and living in large groups. (The upper limit appears to be about 13 kg [29 lb]).
Diana Monkey The Diana monkey (Ceropithecus diana) is one of the most active monkeys in the Taï Forest. Diana monkeys have a highly visible black face framed by a striking white beard. They are noisy, fast moving, and on high alert for predators. Through their vocalized early detection of predators, they provide an important warning system to other primates in the vicinity.
Some of our best understanding of primate predation is derived from the study of primate skeletal remains recovered from eagle nests, most of which are enormous. Study of the contents of these nests in the Taï Forest, Ivory Coast (see pp. 170–71), provides important insight into not only what African crowned eagles hunt but also the manner in which the primates are killed and processed for food. In this setting, scientists have studied more than 1,200 bones from nests, representing about 35 species routinely preyed upon in this corner of West Africa. Some of these prey species weigh upwards of three to four times the size of the eagle predators. Anthropologists’ study of the primate remains—sometimes numbering in the hundreds of bones—provides a remarkably complete story of predator–prey interactions.
The study of these primate bones also shows that the eagles have a clear pattern of processing their prey. They first disable the primates by powerfully thrusting their sharp talons and beaks. The eagles then dismember their victims on the ground. They place portions of the flesh in nearby trees. Via forays from these cache sites, the eagles carry food to the nest for consumption by young eagles. The dismemberment of the prey’s carcass explains why there are no complete skeletons of prey found in the nests or on the ground below the nests. It also means that transport of parts does not require the thrust to lift even the largest of the primates. These findings have important implications for the predation of primates generally, including ancient hominins. We now know that raptors prey on primates. This finding means that primate social behavior and social organization are almost certainly influenced by the behavior of birds of prey—and likewise were influenced in the distant past.
Based on Goodall’s research and a great deal of work since, anthropologists have identified three central features about chimpanzees’ tool use. First, chimpanzees are extraordinarily intelligent and have the complex cognitive skills necessary for at least some kinds of behaviors that require learning and the ability to understand complex symbolization. The evidence for this ability is impressive, and it is growing. For example, chimpanzees are able to accomplish a number of complex behaviors for which visual acumen and ability to think abstractly are essential elements. In laboratory or otherwise controlled settings, humans have taught young chimpanzees to crack open nuts with stones. In turn, these chimpanzees have taught other young chimpanzees to crack open nuts. Chimpanzees have also been shown how to use a sharp stone tool to cut a cord in order to gain access to food in a box. Similarly, they have been shown how to make simple stone tools, and they subsequently have passed on that behavior to relatives.
Second, in natural settings where chimpanzees have not been taught by humans, mothers have also shown their young how to use tools (Figure 7.7). Most of the tools chimpanzees produce are for acquiring and consuming food. Among the rare examples of primate tool use unrelated to food is that of chimpanzees in Gombe throwing stones as part of a dominance conflict between adult males. One of chimps’ most fascinating food-based innovations, observed by the American primatologist Jill Pruetz at Fongoli, Sénégal, is the creation and use of a spearlike object—a trimmed, pointed twig—to skewer strepsirrhines, especially galagos, for food (Figure 7.8). This is the only known setting where a nonhuman animal has been observed to hunt vertebrate prey using a tool purposefully prepared for this single task.
FIGURE 7.7Chimpanzee Social Learning A chimpanzee juvenile watches its mother crack open palm nuts with a stone hammer and anvil in Guinea, West Africa.
Third, tool production and tool use are sometimes highly localized. For example, although some adjacent chimpanzee groups use stones to crack open hard-shelled nuts, only one group has been observed to produce and use simple spears and these tools have not been seen anywhere else in Africa.
While chimpanzees do not depend on material culture for survival—certainly not to the extent of living humans—they nonetheless use material culture. Laboratory experiments and natural-setting research from a range of places in Africa show that chimpanzees use several forms of tools and that not all forms occur in all chimpanzee groups. Perhaps local traditions are passed from generation to generation via social learning—parents pass the information to offspring, and the young share it with other young. In at least one setting in the Budongo Forest, Uganda, researchers found a clear kin-based association with mothers passing knowledge on to their young. In a very real sense, then, tool use in primates is an important form of social and cultural transmission. Moreover, the widespread nature of chimpanzee tool use suggests that it dates back to antiquity. Sites in Ivory Coast, West Africa, contain chimpanzee tools from 4,000 to 5,000 yBP, but tool use likely started earlier.
FIGURE 7.8Chimpanzee Spears (a) A chimpanzee made this spear from a tree branch, sharpening one end with its teeth. (b) Chimpanzees who make such spears use them to thrust into the hollows of trees and kill bushbabies. Here, an adolescent female holds a dead bushbaby that had been killed with the use of a spear. This method is the first (and only) observation of primates’ use of tools to hunt other vertebrates, including other primates.
What about other primates? Field observations by the Swiss anthropologist Carel van Schaik and his associates show that, like chimpanzees, orangutans in Borneo and Sumatra habitually use probes to obtain insects for food. Across the Atlantic in South America, psychologist Dorothy Fragaszy and her research team have documented how some capuchin (Cebus) monkeys use stones to dig for food and to crack open nuts. The complexity here is far less than that of human technology, but these simple behaviors show that chimpanzees are not the only primates that interact with the environment through tools they make.
