|Continued from page 1
When Jane Goodall first watched chimpanzees make simple stick tools to probe into termite mounds, it became clear that tool cultures are not unique to human societies. Of course many animals use tools. Sea otters on the California coast forage for abalones, which they place on their chests and hammer open with stones. Egyptian vultures use stones to break the eggs of ostriches. But these are simple, relatively inflexible lone behaviors. Only among chimpanzees do we see elaborate forms of tools made and used in variable ways, and also see distinct chimp tool cultures across Africa. In Gombe National Park in Tanzania, termite mounds of red earth rise 2 meters high and shelter millions of the almond-colored insects. Chimpanzees pore over the mounds, scratching at plugged tunnels until they find portals into the mounds interior. They will gently insert a twig or blade of grass into a tunnel until the soldier termites latch onto the tools with their powerful mandibles, then theyll withdraw the probe from the mound. With dozens of soldier and worker termites clinging ferociously to the twig, the chimpanzee draws the stick between her lips and reaps a nutritious bounty.
Segue 2,000 kilometers westward, to a rainforest in Côte dIvoire. In a forest filled with twigs, chimpanzees do not use stick tools. Instead, chimpanzees in Taï National Park and other forests in western Africa use hammers made of rock and wood. Swiss primatologists Christophe and Hedwige Boesch and their colleagues first reported the use of stone tools by chimpanzees 20 years ago. Their subsequent research showed that Taï chimpanzees collect hammers when certain species of nut-bearing trees are in fruit. These hammers are not modified in any way as the stone tools made by early humans were; they are hefted, however, and appraised for weight and smashing value before being carried back to the nut tree. A nut is carefully positioned in a depression in the trees aboveground root buttresses (the anvil) and struck with precision by the tool-user. The researchers have seen mothers instructing their children on the art of tool use, by assisting them in placing the nut in the anvil in the proper way.
So chimpanzees in East Africa use termite- and ant-fishing tools, and West African counterparts use hammers, but not vice versa. These are subsistence tools; they were almost certainly invented for food-getting. Primatologist William McGrew of Miami University of Ohio has compared the tool technologies of wild chimpanzees with those of traditional human hunter-gatherer societies. He found that in at least some instances, the gap between chimpanzee technology and human technology is not wide. The now-extinct aboriginal Tasmanians, for example, possessed no complex tools or weapons of any kind. Though they are an extreme example, the Tasmanians illustrate that human culture need not be technologically complex.
As McGrew first pointed out, there are three likeliest explanations for the differences we see among the chimpanzee tool industries across Africa. The first is genetic: perhaps there are mutations that arise in one population but not others that govern tool making. This seems extremely unlikely, just as we would never argue that Hindu brides wear red while Western brides wear white due to a genetic difference between Indians and Westerners. The second explanation is ecological: maybe the environment in which the chimpanzee population lives dictates patterns of tool use. Maybe termite-fishing sticks will be invented in places where there are termites and sticks but not rocks and nuts, and hammers invented in the opposite situation. But a consideration of each habitat raises doubts. Gombe is a rugged, rock-strewn place where it is hard to find a spot to sit that is not within arms reach of a few stones, but Gombe chimpanzees do not use stone tools. The West African chimpanzees who use stone tools live, by contrast, in lowland rainforests that are nearly devoid of rocks. Yet they purposely forage to find them. The tool-use pattern is exactly the opposite of what we would expect if environment and local availability accounted for differences among chimpanzee communities in tool use.
But wait. I said earlier that human culture must have a symbolic element. Tools that differ in form and function, from sticks to hammers to sponges made of crushed leaves, are all utterly utilitarian. They tell us much about the environment in which they are useful but little about the learned traditions that led to their creation. Human artifacts, on the other hand, nearly always contain some purely symbolic element, be it the designs carved into a piece of ancient pottery or the Stanley logo on my new claw hammer. Is there anything truly symbolic in chimpanzee culture, in the human sense of an object or behavior that is completely detached from its use?
Photos courtesy Craig Stanford
Years of living cheek-to-jowl with chimps has made Craig Stanford top banana in the world of ape science.
The Astonishing LAGQ