Are We Smart Enough to Know How Smart Animals Are?(24)

Ben Beck gave us the best-known definition of tool use, of which the short version goes as follows: “the external deployment of an unattached environmental object to alter more efficiently the form, position, or condition of another object.”17 Though imperfect, this definition has served the field of animal behavior for decades.18 Tool manufacture can then be defined as the active modification of an unattached object to make it more effective in relation to one’s goal. Note that intentionality matters a great deal. Tools are brought in from a distance and modified with a goal in mind, which is the reason traditional learning scenarios, which revolve around accidentally discovered benefits, have such trouble explaining this behavior. If you see a chimpanzee strip the side branches off a twig to make it right for ant fishing, or collect a fistful of fresh leaves and chew them into a spongelike clump to absorb water from a tree hole, it is hard to miss the purposefulness. By making suitable tools out of raw materials, chimpanzees are exhibiting the very behavior that once defined Homo faber, man the creator. This is why the British paleontologist Louis Leakey, when he first heard about such behavior from Goodall, wrote her back, “I feel that scientists holding to this definition are faced with three choices: They must accept chimpanzees as man, they must redefine man, or they must redefine tools.”19

After the many observations of chimpanzee tool use in captivity, seeing tool use in the wild by the same species did perhaps not come as a surprise, yet its discovery was crucial since it could not be explained away by human influence. Moreover, wild chimps not only use and make tools, but they learn from one another, which allows them to refine their tools over generations. The result is more sophisticated than anything we know in zoo chimps. A good example are the toolkits, which can be so complex that it is hard to imagine that they were invented in a single step. A typical one was found by the American primatologist Crickette Sanz in the Goualougo Triangle, Republic of Congo, where a chimpanzee may arrive with two different sticks at a particular open spot in the forest. It is always the same combination: one is a stout woody sapling of about a meter long, while the other is a flexible slender herb stem. The chimp then proceeds to deliberately drive the first stick into the ground, working it with both hands and feet the way we do with a shovel. Having made a sizable hole to perforate an army ant nest deep under the surface, she pulls out the stick and smells it, then carefully inserts her second tool. The flexible stem captures bite-happy insects that she pulls up and eats, dipping regularly into the nest below. Apes often climb off the ground, moving onto tree buttresses, to avoid the nasty bites of colony defenders. Sanz collected more than one thousand such tools, which shows how common the perforator-dipping combination is.20

More elaborate toolkits are known for chimpanzees in Gabon hunting for honey. In yet another dangerous activity, these chimps raid bee nests using a five-piece toolkit, which includes a pounder (a heavy stick to break open the hive’s entrance), a perforator (a stick to perforate the ground to get to the honey chamber), an enlarger (to enlarge an opening through sideways action), a collector (a stick with a frayed end to dip into honey and slurp it off), and swabs (strips of bark to scoop up honey).21 This tool use is complicated since the tools are prepared and carried to the hive before most of the work begins, and they will need to be kept nearby until the chimp is forced to quit due to aggressive bees. Their use takes foresight and planning of sequential steps, exactly the sort of organization of activities often emphasized for our human ancestors. At one level chimpanzee tool use may seem primitive, as it is based on sticks and stones, but on another level it is extremely advanced.22 Sticks and stones are all they have in the forest, and we should keep in mind that also for the Bushmen the most ubiquitous instrument is the digging stick (a sharpened stick to break open anthills and dig up roots). The tool use of wild chimpanzees by far exceeds what was ever held possible.

Chimpanzees use between fifteen and twenty-five different tools per community, and the precise tools vary with cultural and ecological circumstances. One savanna community, for example, uses pointed sticks to hunt. This came as a shock, since hunting weapons were thought to be another uniquely human advance. The chimpanzees jab their “spears” into a tree cavity to kill a sleeping bush baby, a small primate that serves as a protein source for female apes unable to run down monkeys the way males do.23 It is also well known that chimpanzee communities in West Africa crack nuts with stones, a behavior unheard of in East African communities. Human novices have trouble cracking the same tough nuts, partly because they do not have the same muscle strength as an adult chimpanzee, but also because they lack the required coordination. It takes years of practice to place one of the hardest nuts in the world on a level surface, find a good-sized hammer stone, and hit the nut with the right speed while keeping one’s fingers out of the way.

The Japanese primatologist Tetsuro Matsuzawa tracked the development of this skill at the “factory,” an open space where apes bring their nuts to anvil stones and fill the jungle with a steady rhythm of banging noise. Youngsters hang around the hardworking adults, occasionally pilfering kernels from their mothers. This way they learn the taste of nuts as well as the connection with stones. They make hundreds of futile attempts, hitting the nuts with their hands and feet, or aimlessly pushing nuts and stones around. That they still learn the skill is a great testament to the irrelevance of reinforcement, because none of these activities is ever rewarded until, by about three years of age, the juvenile starts to coordinate to the point that a nut is occasionally cracked. It is only by the age of six or seven that their skill reaches adult level.24