Kanzi: The Ape at the Brink of the Human Mind (38 page)

In 1949, the British anthropologist Kenneth P. Oakley published a classic book,
Man the Tool-Maker
. This short volume encapsulated what was widely held to set humans apart as unique: “Possession of a great capacity for conceptual thought, in contrast to the mainly perceptual thinking of apes and other primates, is now generally regarded by comparative psychologists as distinctive of man,” he wrote. “The systematic making of tools of varied types required not only for immediate use but for future use, implies a marked capacity for conceptual thought.”
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The notion of man the tool-maker struck a receptive chord in the minds of anthropologists, and in society in general: Alone among the world’s species, tool-making
Homo sapiens
fashions an elaborate culture and manufactures a powerful technology, through which the world has been forever changed.

When Jane Goodall in the early 1960s reported her observations of chimpanzees making simple tools for harvesting ants and termites, human uniqueness appeared to be threatened. In their tool-making, chimps broke twigs from trees, stripped off the leaves, and then inserted the “fishing stick” into termite mounts or onto ant trails. Tool-using of various kinds has been observed in many creatures, from sea otters, to sand digger wasps, to Galapagos finches. But Goodall’s chimps were doing more than
using
tools; they were
making
them. So perhaps
Homo sapiens
isn’t unique, after all? The anthropologists’ response was, Ah, but humans use tools to make tools, while chimps just use their hands and teeth. Human uniqueness was thereby preserved.

The ability to make and use tools has long been considered part of the evolutionary package that transformed an apelike creature into the human species. Charles Darwin argued that stone tools were vital as weapons and provided a substitute for the teeth and claws possessed by other large predators. “The free use of the arms and hands, partly the cause and partly the result of man’s erect position, appears to have led in an indirect way to other modifications of structure,” he wrote in his 1871 book,
The Descent of Man
. “The early male progenitors of man were . . . probably furnished with great canine teeth; but as they gradually acquired the habit of using stones, clubs, or other weapons, for fighting with their enemies, they would have used their jaws and teeth less and less.”
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A century later, when the human prehistoric record was much richer than in Darwin’s time, anthropologists continued to view tools as an integral part of the evolutionary wedge that separated humans from apes, specifically in arming humans as hunters. “In a very real sense our intellect, interests, emotions, and basic social life—all are evolutionary products of the success of the hunting adaptation,” said two prominent anthropologists at a landmark scientific meeting in 1966. “Human hunting is made possible by tools.”
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The shift to becoming a tool-maker—and specifically, a maker of stone tools—has been seen as central to what differentiated humans from apes in an evolutionary sense. By definition, therefore, the very first members of the human family must have been tool-makers. This assumption has been challenged in the past several decades by the many discoveries of ancient human fossils and artifacts from East Africa, and by molecular biological information on modern humans and apes. The first members of the human family are now known to have evolved at least five million years ago, perhaps as many as eight million. And yet, the first recognizable stone artifacts date only to two and a half million years ago. The arrival of these stone tools in
the record coincides with the first appearance of the genus
Homo
, which eventually gave rise to modern humans. The obvious assumption is that this new, large-brained member of the human family was the tool-maker; and that tool-making and increased brain size were linked in some way.

Whatever the truth is of that assumption—and it is difficult to imagine how it might firmly be substantiated—it raises an important question for archeologists and psychologists about the earliest tool-makers: Were they doing something that was beyond the cognitive capability of apes? Or were they merely bipedal apes who were applying their apelike cognitive skills to non-apelike activities?

Nick told me that he had been musing over this question for a long time, and had once approached the Gorilla Foundation with a proposal for an experiment, to see if gorillas could learn to make stone tools. The foundation was busy with other projects, and turned down Nick. It was, he said, an idea in search of a collaborator. His proposal was to motivate Kanzi to make stone flakes, not teach him with structured lessons. “We want to avoid the criticism of classical conditioning,” he said. He suggested we would need a box with a transparent lid. Something enticing would be put in the box, and the lid would be secured with a length of string. Kanzi could be shown by example how to make flakes—by knocking two rocks together, for which the proper archeological term is hard-hammer percussion—but there would be no active teaching, no shaping of his hands, no breaking the task down into component parts.

A little more than a decade ago Richard Wright, of the Bristol Zoo in England, had taught an orangutan to make stone flakes and to use them to cut string to reach a food reward. But Wright had taught the orangutan each component of the task separately. He had also arranged it so that one of the rocks was secured to a plank of wood, not held in the hand as tool-makers did, and Kanzi would. Although Wright’s experiment stands as an important part of primatological research, what Nick had in mind would go further. Wright had taught the orangutan the behavioral components of the task, while our approach would be to impart the conceptual components.

I made some suggestions to Nick about how the design of the food box, or tool site as we came to call it, could be improved. Nick had underestimated Kanzi’s inclination and ability to tear flimsy objects apart, especially if there is food inside. We talked a little about how to carry out tool-making activities so that Kanzi might want to emulate us. And Nick promised to get in touch with me after we returned to the United States. This he did within a couple of weeks, and I told him that we had made a tool site to his specifications. A week later he arrived at the Language Research Center with fellow archeologist Kathy Schick, their truck laden with a thousand pounds of rock.

In 1989, Tom Wynn, an archeologist, and Bill McGrew, a primatologist, published a paper called “An Ape’s View of the Oldowan.” The word Oldowan is the name applied to the earliest known stone-tool assemblages, which were found in Africa and date back to two and a half million years ago. The question Tom and Bill addressed in their paper—“When in human evolution did our ancestors cease behaving like apes?”—was essentially the same as Nick’s.
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In other words, given the right circumstances, could apes make Oldowan tools? Tom and Bill’s approach to the question was not experimental, as Nick planned, but instead involved examining the skills required to make Oldowan tools, and then seeking signs of such skills in aspects of chimpanzees’ lives.

The artifacts that make up Oldowan assemblages were produced from small cobbles, and they include about half a dozen forms of so-called core tools, such as hammerstones, choppers, and scrapers, and small, sharp flakes. The tool-makers were assumed to have had mental templates of these various tool types, which they used to produce tools for a range of different functions. The tools are often found in association with broken animal bones, which sometimes show signs of butchery. The clear inference is that, beginning about two and a half million years ago, our human ancestors began exploiting their environment in a non-apelike way, by using stone tools as a means of including significant amounts of meat in their diet.

Until quite recently, archeologists argued that the earliest tool-makers lived lives analogous to those of contemporary hunter-gatherers. In other words, they organized themselves into small, mobile bands, established temporary home bases, and divided the labor of hunting and gathering between male and female members of the band. This was a very humanlike way of life, albeit in primitive form, and most definitely unlike that of an ape.

In recent years, however, a reexamination of the archeological evidence has changed this picture dramatically, making it much less humanlike and more apelike. There is no question that these early members of the human family made tools and butchered animal carcasses. But there is considerable debate over the extent to which they were active hunters as opposed to opportunistic scavengers. And the notion of home bases and a division of labor between the sexes has been abandoned as untenable. The earliest tool-makers are now viewed as bipedal apes who lived and foraged in social groups in a woodland/savannah environment, as baboons and chimpanzees do, and whose repeated use of specific locales for butchery activities created the archeological sites that are being uncovered today.

An equally important shift of perspective has taken place regarding the tool assemblages themselves. In her pioneering work in East Africa in the 1940s, 1950s, and 1960s, Mary Leakey identified what she assumed were intentionally produced tool types. But when Nick Toth began a program of experimental archeology in the 1970s, in which he became a proficient maker of Oldowan artifacts himself, he came to a very different view. “My experimental findings suggest that far too much emphasis has been put on cores at the expense of flakes,” he wrote. “It seems possible that the traditional relationship might be reversed: the flakes may have been the primary tools and the cores often (although not always) simply the by-product of manufacture. . . . Thus the shape of many early cores may have been incidental to the process of manufacture and therefore indicative of neither the maker’s purpose nor the artifact’s function.”
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Nick’s reassessment of the Oldowan artifacts revolutionized African archeology, and further changed the perception of
the humanness of the earliest tool-makers. According to this new theory, the half dozen different tool types in Oldowan assemblages were not the product of mental templates in the minds of sophisticated tool-makers; instead, they were the results largely of the shape of the cobble from which the flakes were struck, and the nature of the raw material. The only skill required by the earliest tool-makers, therefore, was that of striking flakes off a core using a hammerstone. How cognitively demanding is such a task?

“One of the more direct ways to assess the cognitive ability employed in tool-use is through examination of spatial concepts,” wrote Tom and Bill in their 1989 paper. “The spatial concepts required for Oldowan tools are primitive. The maker need not have paid any attention to the overall shape of the tool; instead, his focus appears to have been exclusively on the configuration of edges.”
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Tom and Bill identified three spatial concepts in relation to tool-making: proximity, boundary, and order. Simplest of the three is proximity, which refers to the ability to land hammer blows repeatedly in the same or more or less the same position on the core cobble. A more complex notion is that of boundary in space, which has to do with the division of a spatial field into different realms. This refers to the process of striking flakes off both sides of a cobble, yielding a bifacial chopper. The most sophisticated spatial notion is that of order, which concerns control over the location of a sequence of hammer blows.

Many Oldowan tools have just two or three flakes removed, while few have more than a dozen. Once the first flake is removed, the direction of subsequent flaking appears to be fixed. The complexity of the tools, in relation to spatial concepts of their manufacture, is therefore rather limited. What of the spatial concepts involved in the natural tool-making of chimps?

Most of the tools chimps make are of raw material other than stone, and so a direct comparison is impossible. And many of the tools’ characteristics are influenced by the nature of the material. For instance, the position of leaves to be stripped from a twig is a property of the plant, not a decision of the ape.
However, suggest Tom and Bill, it is possible to find examples of the three spatial concepts in several realms of chimp behavior. For instance, chimpanzee “artists” do not scrawl randomly on blank pieces of paper. And if they are given a sheet of paper on which a geometric shape, such as a square, has been drawn, chimps tend to mark on or near the shape, thus displaying the concept of proximity. They exhibit the property of boundary in the preparation of sedge stems as termite fishing-probes. The stem is triangular in cross section, and the chimps carefully remove one of the ridges by longitudinal stripping. Finally, the concept of order is to be found in chimpanzees’ nest building, a skill that is learned rather than innate, as it is in birds. When a chimp builds a nest, the choice of the first major branch to be bent provides the foundation of the subsequent pattern of interweaving of smaller branches and twigs.

For Tom and Bill, the conclusion was clear: “All the spatial concepts for Oldowan tools can be found in the minds of apes. Indeed, the spatial competence described above is probably true of all great apes and does not make Oldowan tool-makers unique.”
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And they respond to the positing of the “using a tool to make a tool” as a Rubicon, by pointing out that Richard Wright’s orangutan learned to do just that, so the skill is within apes’ cognitive realm. Moreover, they make the reasonable point that chimps have sharp teeth, and use them to fashion wooden tools; they don’t need stone flakes for the job. “We cannot fault apes for not employing unnecessary techniques in making tools needed in their subsistence,” they add.
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