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FEATURE ARTICLE

Chimpanzee Hunting Behavior and Human Evolution

Chimpanzees are efficient predators that use meat as a political and reproductive tool. Are there implications for the evolution of human behavior?

Craig Stanford

Early Hominid Behavior

The early hominids were probably at least as socially complex as modern chimpanzees. The hunting ecology of the chimpanzee suggests the following: Most meat-eating took place within the home range of the social group and most frequently within a core area smaller than the total range. Most of the prey were small animals, weighing less than 25 kilograms. Most of the hunters would have been males, and the rate of success was linked to the number of hunters in a party. The meat was probably shared by members of the hunting party as well as by any females who might have been present. Meat may have been used by males for selfish political reasons and for gaining sexual access to females. If so, we would expect a degree of sexual selection for the best hunters.

Some recent fossil discoveries in Ethiopia support such an idea. A multinational expedition led by the American anthropologist Tim White, the Japanese anthropologist Gen Suwa and the Ethiopian anthropologist Berhane Asfaw recently unearthed the fossilized remains of the oldest known hominid species, Australopithecus ramidus. These primitive hominids lived about 4.4 million years ago, perhaps one million years after the evolutionary branching of the ancestral lines leading to modern chimpanzees and human beings. The fossil deposits indicate that these early australopithecines inhabited a forested environment, which they shared with colobus monkeys, small antelopes and other ground-dwelling vertebrates. As yet there is no direct evidence that the early hominids were preying on these animals; all we can say is that they had the opportunity to do so.

The fossils do suggest that some behavioral differences between chimpanzees and hominids had already emerged. For one thing, Australopithecus ramidus was a biped; its lower body was clearly adapted for walking on the ground. The first hominids may have continued to use trees for gathering fruit and for shelter at night, but their ground-dwelling habits would certainly have made it a little more difficult for them to catch the arboreal ancestors of modern colobus monkeys. Of course, this does not deny the possibility of hunting monkeys, since a hunting party could have flushed out an animal by driving it from one hunter to another once it was cornered in an isolated tree. Whether the hominids concentrated on colobus monkeys to the same extent that the Gombe chimpanzees do is another matter. Some other prey species, perhaps antelope, were also available.

The australopithecines also differed from modern chimpanzees in having relatively small canine teeth. But again, this does not mean that they did not eat meat. Although large canines are often taken to be an indicator of a meaty diet, they are more likely to be used as weapons by males in the competition for mates. Chimpanzees do not use their canines to capture adult colobus monkeys; rather they tend to grab the animals and flail them to death.

Finally, a number of anthropologists have suggested that the carcasses of large mammals were an important source of meat for early hominids once they had developed the use of stone tools. Did the early hominids eat meat before the development of stone tools 2.5 million years ago? Given the behavior of the chimpanzee, it seems likely that they did, but the relative significance of meat in their diet remains open to conjecture. Although a scavenging life-style is frequently suggested for the early hominids, modern chimpanzees in the wild have little interest in dead animals as food. When scavenging does take place, the female chimpanzees at Gombe do show more interest than do the males; the females are also more adept at using tools. The same may have been true of the earliest hominids.

The role of hunting in the lives of the earliest hominids was probably as complex and politically charged as it is in modern chimpanzees. The early hominids may even have been important predators in their ancient forest ecosystems. When we ask the question, "when did meat become an important part of the human diet?" we should look well before the evolutionary split between apes and human beings in our own family tree.

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