Kanzi: The Ape at the Brink of the Human Mind (40 page)

Kanzi had become a tool-maker. But our question was, how good a tool-maker is he? Could he have stood shoulder to shoulder with the makers of Oldowan tools, striking flakes off cores as effectively as they did? Nick’s experience as an Oldowan tool-maker offered us a way of addressing these questions.

Through teaching himself to make the apparently simple core forms and flakes of the Oldowan, Nick came to understand both the process of flaking and the product. “The mechanics of flaking stone are not intuitively obvious,” he told me.
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When he tried to teach me and some of the other Wenner-Gren conferees how to flake that afternoon on the beach in Portugal, I could understand what he meant. I was impressed by how very difficult it is to produce flakes, and the challenge is not simply to hit the core with sufficient force. You have to know where to aim the hammer blow, and how to deliver it.

The initial inclination of the naive stone knapper is to hit the core hard enough so that a flake will pop out of the core, as if it were being chiseled out. But, as Nick demonstrated, the flakes come from the bottom of the core, not the top. The best everyday example of the principle of concoidal fracture at work in stone tool-making is the effect of a tiny pebble hitting a window: A cone of glass is punched out of the pane, and the exact shape of the cone is determined by the direction at which the stone hits the glass.

For effective flaking by hard-hammer percussion, three conditions have to be met. First, the core must have an acute edge (one with an angle of less than 90°). Second, the core must be struck with a sharp, glancing blow, hitting about half an inch from the edge. And third, the blow must be directed through an area of high mass, such as a ridge or a bulge. With these conditions met, and starting with suitable raw material, one can form long, sharp flakes. Oldowan assemblages were often made from lava cobbles, which had been rounded through being carried along stream or river beds. The tool-makers sometimes struck flakes from one side of a cobble, producing the unifacial form of a chopper, or along two sides, yielding a bifacial form. Whatever forms are produced, they have the appearance of great simplicity. But as Nick correctly points out, “It is the process, not the product, that reveals the complexity of Oldowan tool-making.”
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Nick and Kathy Schick recently drew up a list of criteria by which to assess the technological sophistication of simple cobble and flake tools. “It was necessary to get beyond relying on gut reaction for distinguishing between true artifacts and naturally fractured stone,” explains Nick.
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The criteria are as follows:

1. Flake angle
   . This is the angle formed between the striking platform of a flake and the dorsal surface of the flake (representing the edge angle of the core before the flake was detached).
   
2. Degree of removal of outer unusable surface
   . Many flint stones are encased in a tough concrete exterior that crumbles when it flakes and is thus unusable as a tool. In order to get to the flint, which is an inner stone that can readily be flaked to produce a sharp edge, it is first necessary to remove this rough outer core. The ratio of remaining usable to unusable material left in the stone after flaking provides an index of how efficiently the stone has been reduced by the activity of flaking. A good knapper will removed virtually all of the unusable material very easily.
   
3. The size of flakes removed
   . The ratio of the size of the largest flake scar to the maximum dimension of the core is a partial indication of how efficiently flakes are being detached from a block of stone.
   
4. The amount of step fractures and battering seen on the stone
   . Step fractures are unclean breaks in the stone. When a stone is hit at exactly the proper angle, a clean flake falls off, leaving the stone surface as smooth as if someone had run a knife through butter. When a stone is flaked at the wrong angle, it breaks off the rock, leaving many jagged edges at the point of the break. If a stone is merely slammed into another hard surface, with little regard for the angle of the blow, it may break, but it will have a battered appearance, looking precisely as though it had been battered. Well-flaked stone looks as though it had been sculpted or chiseled.
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Measured against these criteria, the products of the earliest tool-makers score highly. “It seems clear that early tool-making proto-humans had a good intuitive sense of the fundamentals of working stone,” observes Nick.
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They knew about angles required on the core, about sharp, glancing blows, and about seeking regions of high mass on the core. They also apparently knew when otherwise suitably shaped cobbles would not flake well.

For instance, Nick noticed that at Koobi Fora in northern Kenya, heavily weathered cobbles were common. Such cobbles flake unpredictably and inefficiently, and a knowledgeable stone knapper would avoid using them. The outward evidence of the weathering, however, is slight and appears merely as hairline fractures on the surface. When Nick examined the Oldowan assemblages at various archeological sites at Koobi Fora, he found only rare evidence of the use of weathered cobbles; their frequency at the sites was far less than their occurrence on the ancient landscape. “It seems clear that the early hominids had already learned to reject such inferior material,” concludes Nick.
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By these measures, therefore, the Oldowan tool-makers displayed considerable technological sophistication and perceptual skills. What of Kanzi? His progress in hard-hammer
percussion has been considerable, moving from the undirected, timid tapping of rocks together to the forceful hammering directed at the edge of the core. Nick describes the process of learning to make tools as being punctuational, with periods of slow change in between. “You suddenly get an insight into what is required, and then slowly improve on that,” he explains.
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Kanzi clearly had an insight into the importance of hitting the rock close to its edge; and he had important insights when he developed his throwing techniques. Despite this, however, he has not yet developed the stone-knapping skills of the Oldowan tool-makers. In a paper reporting the first eighteen months of the project, we described our assessment of Kanzi as follows:

So far Kanzi has exhibited a relatively low degree of technological finesse in each of [the four criteria] compared to that seen in the Early Stone Age record. The amount of force he uses in hard-hammer percussion is normally less than ideal for fracturing these rocks. His flake angles when using hard-hammer percussion tend to be steep (approaching 90°), while Oldowan flakes were generally detached from more acute-edged cores (flake angles typically 75°-80°). As yet, Kanzi’s cores retain a very high proportion of their original cortex and are steep-edged and rather battered. The flakes he produces tend to be relatively small (generally less than 4 cm long) and often stepped or hinged, and his cores generally exhibit marginal (non-invasive) flake scars.
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There is, therefore, a clear difference in the stone-knapping skills of Kanzi and the Oldowan tool-makers, which seems to imply that these early humans had indeed ceased to be apes. It isn’t yet certain, however, whether Kanzi’s poorer performance is the result of a cognitive or an anatomical limitation. Or simply lack of practice. Certainly most of us working with Kanzi are unable to make stone tools ourselves. Without a good teacher and constant practice it is a very difficult skill to acquire. Were an anthropologist to excavate our site a million years from now, I doubt that he or she could distinguish between the human stone artifacts and those produced by Kanzi—except, of course,
those that were made by Nick. Making stone tools is not easy and does not seem to be a skill that normal human beings acquire readily with little instruction, as we are asking Kanzi to do.

Nick hopes to learn whether or not Kanzi, with minimal demonstration, can acquire a skill that took, at best, many generations for our ancestors to perfect. If Kanzi does not succeed in matching the skills of Oldowan tool-makers in the span of one research career, it would still be foolish to rule out the potential of the ape mind to do so, given a few generations of exposure to need to use such tools.

The structure of bonobos’ arms, wrists, and hands is different from that of humans, and this structure constrains the ability to deliver a sharp blow by snapping the wrist, a movement that Nick considers important in effective tool-making. I suspect that if Kanzi is limited in the quality of flaking through hard-hammer percussion, it is the result of biomechanical, not cognitive, constraints. His ape hands, with long, curved fingers and short thumbs, prevent him from gripping the stones efficiently enough to allow him to deliver a powerful, glancing blow.

The greatest surprise of the tool-making project was Kanzi’s development of throwing as a way of obtaining sharp edges. Not only did it reflect a problem-solving process in Kanzi’s mind, but it also produced material that addresses an important archeological problem: What did early humans do
before
they made Oldowan tools? Application of the criteria mentioned earlier to identify genuine artifacts as compared with naturally fractured stone would reject Kanzi’s flakes and cores as tools. And yet they are artifacts, and they can be used as effective cutting tools.

Some of Kanzi’s cores look rather similar to Oldowan core tools, acknowledges Nick, but most do not, because of the angles and preponderance of small flake scars. “If I were surveying a Stone Age site and found some of these things, I’d definitely check them out, but I would almost certainly conclude they were naturally flaked,” he says. But if pre-Oldowan tool-makers used Kanzi’s approach, and smashed rocks by throwing them, how could an archeologist know? “Most natural processes that break rocks also tend to smooth them,” explains Nick. “Rocks may fracture as they crash into each other while rolling along a stream bed, but the rolling process quickly dulls the edges.”

Finding a sharp-edged cobble with angles of close to 90° might therefore be indicative of primitive tool-making. “You have to examine the context of the rock, to eliminate natural processes that might have produced sharp edges. But after seeing these incipient flaking skills with Kanzi, we certainly have to consider it as a possible model for the earliest stone tool-making. He has taught us what we should be looking for, to find tool-makers earlier than what we usually call ‘the earliest tool-makers.’”
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When I agreed to participate in the Wenner-Gren conference I had no idea a collaboration such as the one with Nick and Kathy would arise. Both sides—in psychology and archeology—benefited tremendously. And Kanzi became the first nonhuman to learn humanlike stone tool-making in a natural setting. Nick joked that Kanzi should be awarded an honorary doctorate, pointing out that he would need a small cap and a gown with long arms. He wasn’t joking, however, when in the spring of 1991, Kanzi was awarded the inaugural CRAFT Annual Award for Outstanding Research Pertaining to Human Technological Origins. Nick and Kathy are co-directors of CRAFT, or the Center for Research into the Anthropological Foundations of Technology, at Indiana University. “The award is justified, because the work with Kanzi has given us one of our most important insights into paleolithic technology,” says Nick. “It has given us a view of what is possible with apes, and an insight into the cognitive background of what is necessary to go further.”