IT IS like a fictitious scene from 2001. An ape-like creature looks thoughtfully at a rock he is gripping purposefully in his hand; he shifts his gaze to the ground, and back to the rock. Then, in a slow, deliberate move, he lifts his arm above his head and forcefully hurls the rock to the ground, where it shatters into a dozen pieces. Quickly scrutinising the fragments, he selects the sharpest of them, runs to a source of food and enthusiastically begins to slice his way into it. A new technology is born. Culture is born.
But this scene is not fiction. It happened in an unusual project at the Language Research Center in Atlanta, Georgia (This Week, 23 February 1991). The creature is not ape-like; he is an ape, specifically, a pygmy chimpanzee or bonobo called Kanzi. Born in 1980, Kanzi has gained fame in recent years for his extraordinary language skills, which he developed under the tutelage of his caretaker, psychologist Sue Savage-Rumbaugh (“Look who’s talking now”, New Scientist, 27 April 1991). Kanzi uses an extensive array of arbitrary symbols as words and understands complex spoken sentences. So how did Kanzi the wordsmith turn rocksmith?
Learning curve
The idea that Kanzi might be able to learn to make stone tools by the same process as early humans was suggested by Nick Toth, an archaeologist at Indiana University in Bloomington, where he is co-director of the Center for Research into the Anthropological Foundations of Technology, or CRAFT. Toth and Savage-Rumbaugh met in March 1990 at a Wenner-Gren Foundation conference on the evolution of language and tool-making at Cascais in Portugal. “Nick’s suggestion intrigued me,” says Savage-Rumbaugh, “and I suggested that he should come to Atlanta to meet Kanzi.” He arrived the following May with his colleague Kathy Schick. Toth and Schick saw the opportunity to address one of the central issues of anthropology: the origin of culture. When in prehistory did our ancestors stop behaving like apes and begin to be recognisably human?
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Until recently, most researchers believed that the transition took place when our early ancestors started to make the first stone tools. Systematically making various tools for immediate and future use, say the traditionalists, implies a great capacity for human-like conceptual and abstract thought. In contrast, the thoughts of apes and other primates are mainly perceptual, limited to the experience of the senses. The first tools were simple, sharp stone flakes and shaped cobbles, known as Oldowan technology, and appeared around 2.5 million years ago in East Africa. The age of these flakes closely matches that of the first known fossils of the genus Homo, to which modern humans belong. To many anthropologists this is more than mere coincidence.
Following the emergence of the first Homo species, the ape-sized brain of our early ancestors began to expand. It has been suggested that as well as tool making, this era saw the emergence of elements of social organisation that are seen in modern hunter-gatherer societies, including division of labour, sharing food resources, and possibly language. In other words, the Oldowan tools were made by a primitive hunter-gatherer society that was certainly protohuman.
But there has been much debate over this traditional view. Five years ago an archaeologist and a primatologist teamed up to write a now classic paper, “An ape’s view of the Oldowan” (Man, vol 24, pp 383-398). Tom Wynn of the University of Colorado at Colorado Springs and Bill McGrew of Miami University in Ohio, said: let’s not simply assume that the Oldowan tools were a mark of humanity in some way, primitive though it may be; let’s look for what is characteristically ape-like about it.
The two researchers said they could find nothing in the tools themselves, in the way they were made, or in the way they were used, that implied that the Oldowans were smarter than modern apes. “There is nothing about the Oldowan which demands human-like behaviour such as language, ritual, shared knowledge of arbitrary design, or other sophisticated mental processes,” they concluded. Their contention was that the earliest tool-makers were no more sophisticated culturally than chimpanzees that walked on their hind legs and had a need for sharp stone flakes.
Sticks and stones
McGrew, the primatologist of the team, had studied the tool-using habits of chimpanzees, which include making termite “fishing” sticks, stone and wooden hammers for cracking nuts, anvils, and ant probes. From this he had come to the conclusion that the cultural life of apes had been underestimated. Maybe, he mused, chimps were perfectly capable of making Oldowan tools. For his part, Wynn had studied the complexity of Oldowan tools and concluded that they were simpler than some had suggested, and that their manufacture would not require any uniquely human attributes. For example, their makers would not necessarily have possessed language.
As Wynn and McGrew pointed out, an experiment in the early 1970s had already shown that an ape can make and use sharp stone flakes. In this experiment at Bristol Zoo, Richard Wright taught an orang-utan to knock a flake off a cobble using a second cobble, and then use the flake to cut a string to gain access to food. “The lack of functional stone flaking in wild chimpanzees does not represent some behavioural or cognitive deficit,” Wynn and McGrew concluded, because the tasks for which the chimps use tools simply do not require sharp edges. Oldowan tools may or may not be more complex than implements made by chimps from grass, leaves and twigs, but the fact that chimps don’t make them doesn’t mean that they can’t, the researchers argued. Perhaps they just do not need them.
Neither are there clear differences in the geometrical concepts required to make the two sorts of tools, they added. Activities such as stripping leaves off a twig or shortening twigs, which chimps do when they are making fishing sticks, demand a grasp of spatial concepts just as complex as that involved in making Oldowan flakes. Nor could Wynn and McGrew find a systematic difference in the groupings of the two types of tool. Although the Oldowan tools are sometimes labelled as choppers, scrapers, discoids and so on, in reality there is a continuum of types. The same applies to the tools apes make: there are no natural groupings.
And finally, they said, there is no clearcut difference to be seen in the manufacturing procedures of apes and the makers of the first stone tools. Anthropologists make much of the fact that the Oldowan tool makers were highly selective in the type of stone they used, sometimes transporting it several kilometres from its source to where it is used; this required planning and foresight. But chimps are also selective of their raw material, countered Wynn and McGrew. The chimps of the Tai Forest in Côte d’Ivoire eat the kernels of panda nuts, which have hard shells, and cola nuts, which have soft shells. The chimps use granite hammers for the panda nuts and quartzite, which is softer than granite, on cola nuts. Furthermore, the chimps often carry these hammers several hundred metres from their source to the nut cracking sites.
One aspect of the manufacturing procedure has traditionally been erected as something of a rubicon, with humans on one side, apes on the other: only humans use tools to make tools, it is said. Wynn and McGrew argued that Wright’s orang-utan used a stone hammer to make a stone flake, so demonstrating that using tools to make tools is not outside an ape’s cognitive ability. Perhaps the real difference is that apes do not need tools to make tools, as they can use their sharp canine teeth to manufacture some of their tools. They simply avoid techniques which are unnecessarily complicated for their purposes, Wynn and McGrew said.
Toth was intrigued by Wynn and McGrew’s paper and the gauntlet it threw down for the traditionalists to pick up. But because of his own experience as a skilled maker of stone tools, he felt there was something missing from their analysis. “It is the process of making them that reveals their complexity,” he says, “not their appearance.” Towards the end of the Cascais conference Toth took everyone down to the beach one afternoon to test out their success at knapping stones to produce sharp fragments. “There were a lot of bruised knuckles,” remembers McGrew, who was an enthusiastic but incompetent participant in the experiment, as was everyone who tried.
Making Oldowan-like flakes is not simply a matter of smacking two rocks against each other. For effective flaking by hard-hammer percussion, as the technique is known, three conditions have to be met. First, the cobble being struck, known as the core, must have an acute edge (one with an angle of less than 90°). Secondly, the core must be struck with a sharp, glancing blow, hitting it about a centimetre from the edge. And thirdly, the blow must be directed through an area of high mass on the stone, such as a ridge or a bulge (see Diagram). The earliest makers of stone tools, around 2.5 million years ago, apparently understood this and routinely produced long, sharp flakes, which are very effective for slicing through hide, or removing meat from a bone. It is possible to produce sharp chips or fragments – which are much less effective by simply smacking two rocks together, as the Cascais participants found out, but not long Oldowan flakes.
If Wynn and McGrew were correct, then an ape should under the right circumstances be able to make long, sharp flakes like those made by the Oldowans. Toth and Schick knew about Wright’s work with the orang-utan, but they also knew it was limited. First of all, Wright’s orang-utan had produced sharp fragments, not Oldowan flakes. Secondly, he had taught the orang-utan piecemeal, breaking the task down into several components and hence making it considerably easier to learn. Eventually the ape was able to take a hammer stone, strike the core (which was secured to a board) to produce a sharp fragment, and then use the fragment to cut a string that held shut a box containing some kind of tasty morsel. But Toth and Schick wanted to see if an ape could learn for itself by observation and by being motivated, as it might in the wild.
The experiment began with Toth sitting outside Kanzi’s enclosure, stone knapping. Kanzi was intrigued by what was going on and would occasionally use one of the flakes to gain access to food in a box secured by a string. He was also encouraged to make flakes of his own, by being given two stones, but there was no attempt to teach him by moulding his hands or moving his arms.
Later, Savage-Rumbaugh or one of her colleagues, Rose Sevcik, took over as demonstrator, this time inside the enclosure. Kanzi quickly learnt to discriminate between flakes, selecting only the sharp ones. And he began knocking two rocks together, tentatively at first but with gathering enthusiasm. With uncharacteristic patience, he would sit stone knapping for long periods, until eventually a sharp chip flew off the core stone. Shouting with glee, he would run with it to the food box, and begin slicing at the string.
Different strokes
During the first few months Kanzi became more and more efficient at producing flakes, small though they usually were. Mostly through trial and error, he learnt to concentrate the blows at the edge of the core, not the centre. But his technique was very different from that of a human knapper. He held the core (usually in his left hand) close to his body, and brought the hammer stone down on it vertically, or sometimes closer to the horizontal and towards his body. A human stone knapper holds the core away from his or her body, and uses a wrist-flicking action to strike it with the hammer stone. Despite these differences, Kanzi’s technique worked well enough and he was obviously learning what was effective and what was not. But he was making sharp fragments, not long Oldowan flakes.
One day, working in an indoor area, Kanzi was evidently getting frustrated by his lack of results. He offered the stones to Savage-Rumbaugh, as if to say “Here, you do it for me.” Savage-Rumbaugh declined, and encouraged him to try harder. But instead of continuing knapping, Kanzi looked first at the rock in his hand, then at the floor, and then back at the rock, evidently thinking about other ways of producing sharp fragments – as described in the opening paragraph. “I was delighted,” recalls Savage-Rumbaugh, “because it demonstrated his ingenuity in the face of a difficult problem.”
From the anthropological standpoint, Toth was less pleased. “The Oldowan tool makers used hard-hammer percussion, not throwing,” he told Savage-Rumbaugh. “If Kanzi throws the rocks, the percussion will be random and we won’t learn anything.” Persuaded by this point of view, Savage-Rumbaugh and her colleagues decided they could thwart Kanzi’s trick by covering the floor with thick matting. When the next tool-making session came round, Kanzi was stunned to find that when he threw the rock at the floor it merely bounced. He tried again, with the same result. Ever resourceful, he looked around for a join where two pieces of matting met, pulled one of them back and threw the rock at the exposed concrete. When Savage-Rumbaugh shows a videotape of this incident to even the most academic of gatherings, there is a whoop of appreciation from the audience: simian genius prevails over human guile.
It wasn’t long, however, before Kanzi worked out another way around the challenge of soft ground, this time in his outside enclosure. He placed one rock on the floor, stood back, and took aim at it with a second. He had invented a new way of flaking – by directed throwing. “He continued to use this technique, and there was no way of stopping him,” says Savage-Rumbaugh. “We had presented Kanzi with a problem and he had figured out the best way to solve it – three times.”
Kanzi steadily improved his throwing technique, mostly by throwing harder and more accurately, consistently hitting the edge of the target stone. But he still made sharp fragments, not Oldowan flakes. Toth, Savage-Rumbaugh and their colleagues concluded that despite Kanzi’s progress, his skill was still not matching that of the Oldowan tool-makers (see “Pan the tool-maker”, Journal of Archaeological Research, vol 20, pp 81-89).
To Toth and Schick, this conclusion is at least consistent with the traditional view that there is a significant cognitive difference between the earliest tool-makers and apes, even if it doesn’t confirm it. It is possible, of course, that Kanzi could not make Oldowan tools because the anatomy of his arms and hands prevents him from doing so. The deficit might be biomechanical, not cognitive. It is possible, too, that the required ability will emerge in time.
“Kanzi can’t do some of the things the Oldowans could,” Wynn admits. But McGrew is not yet prepared to concede the point. “In the situation Kanzi was put, he made sharp edges that did the job,” says McGrew. “What would happen if he were in ecological circumstances that required Oldowan-like flakes? Maybe he would make them then.” Savage-Rumbaugh also thinks it is too soon to make a final judgment, and that Kanzi might yet learn. When humans learn stone knapping, the ability to make Oldowan flakes is often an “aha!” kind of experience, a sudden development in which by some intuitive means they understand what needs to be done, even though they often cannot describe it. Kanzi’s present lack of progress towards making Oldowan flakes therefore cannot be taken as proof he will never do it.
New insight
Whatever the final level of achievement for Kanzi the tool-maker, the experiment has produced an unexpected archaeological insight. Until now, if stone fragments matched the criteria for products of hard-hammer percussion, they were judged to be human-made. If they did not, they were said to be the product of natural stone-breaking processes, such as rock falls, with no protohuman input. “Kanzi has shown us what to look for if we want to know what a pre-Oldowan tool technology might look like,” observes Schick. “What he produces may be a good model for the earliest stone technologies.”
Two years ago, Kanzi was presented with the inaugural CRAFT Annual Award for Outstanding Research Pertaining to Human Technological Origins. “The award is justified, because the work with Kanzi has given us one of our most important insights into palaeolithic technology,” says Toth. “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.” When Kanzi was presented with a certificate commemorating the award back in Atlanta, he walked over to his keyboard, scrutinised the symbols carefully, and pressed the key that said “Surprise!”.
