OLDOWAN HOMINIDS AS BIPEDAL
CHIMPANZEES?(Pages 133-142)
ARTIFACTS AS REFLECTIONS OF INTELLIGENCE
What do these patterns of stone artifacts tell us about the cognitive abilities and intelligence of Oldowan tool makers? Although the products of Oldowan technology are quite simple, the processes required in the hominid mind to produce these forms show a degree of complexity and sophistication: in other words, skill. We feel that these early stone tool-making hominids had evolved, by 2.4 to 1.5 million years ago, to an important new level of intelligence and cognitive operations not present in earlier hominids or in modern nonhuman primates, including the highly intelligent apes.
It is clear to us that efficient flaking of stone requires a strong intuitive knowledge of three-dimensional geometry as well as sophisticated motor skills in order to detach flakes from cores. This is a skill that take a number of hours to master, even for a modern human. previously mentioned, to efficiently flake stone, one is constantly searching for acute angles on core edges from which to detach flake A carefully controlled, sharp, glancing blow from the hammer stone the core is required to initiate fracture. This level of cognitive optional skill and motor control has not been documented in nonhuman primates in the wild.
OLDOWAN HOMINIDS AS BIPEDAL
CHIMPANZEES?
Recently several researchers, such as primatologist William McGrew of the University of Sterling and archaeologist Thomas Wynn of the University of Colorado, have posed an intriguing question: Could the cognitive processes of Homo habilis essentially be on a par with those of modern apes and the differences that exist be due primarily to ecological, dietary, and technological differences rather than differences in intelligence levels?
Wynn has applied an interesting methodology used by cognitive scientists to examine the developing complexity of cognitive processes modern human children. Using criteria proposed by the Swiss psychologist Jean Piaget, he analyzed Oldowan tools using the geometric concepts of proximity, separation, and order. Wynn concludes that Oldowan tool makers exhibited preoperational intelligence, similar to that of modern chimpanzees and very young children, and that these early hominids did not exhibit any cognitive complexity above that the African apes.
Although we would agree that the products of Oldowan technology do not show many clear signs of deliberate or stylistic design, we would argue that the technological processes that produced these forms probably do exhibit higher cognitive capabilities than are observed among modern apes.
Is there another, more direct way to test how the thought process of Oldowan tool makers were similar to or different from those modern apes? Although anthropologists can compare endocranial cc casts of the inner surface of the skull case, which preserve the morphology of the brain) of apes, modern humans, and fossil hominids, such anatomical information cannot show us the actual capacities of these animals. And since modern African apes are not know produce flaked stone artifacts in the wild (the principal behavioral manifestation left behind by Oldowan hominids), comparisons of the material cultures of these different creatures is difficult as well.
There is, however, another approach we can take to attempt meaningful comparisons between the cognitive abilities of early tool-making hominids and those of modern apes. If we could teach modern apes the basics of flaking stone tools, give them a reason to do it, and then allow them to develop their own expertise and abilities, we could then compare apes and early hominids in terms of their tool-making abilities. We know that apes are smart and that they can be taught a variety of complex tasks. But we wanted to see, given only the very basics of stone tool making, how far a modern ape could take it.
PAN THE TOOL MAKER
The ideal opportunity to study the technological capabilities of a modern African ape presented itself in 1990 at a conference in Portugal on tools, language, and cognition, organized by the Wenner-Gren Foundation for Anthropological Research. Psychologist and primatologist Susan Savage-Rumbaugh presented research results of communication studies with apes. We had been wanting for several years to collaborate with primate researchers on comparative studies of ape and hominid technology, and finally we met someone who also thought this would be a great idea.
Now we would have the opportunity to see if a bonobo, one of the two species of chimpanzees, could learn to make stone tools and, if so, how its actual tool-making procedures and the artifacts it might make would compare with the earliest tools produced by our hominid ancestors. Basically we hoped, if the bonobo did indeed get involved in making stone tools, to be able to see if its tools really differed very much from those the Oldowan hominids were making. Or were the earliest stone tool makers significantly advanced beyond what an ape is capable of?
Our van heavily laden with stone cobbles, we drove from Indiana University to the Language Research Laboratory in Atlanta, Georgia, operated jointly by Georgia State University and the Yerkes Regional Primate Research Laboratory of Emory University. Here, chimpanzees and other primates are raised in an incredibly nurturing environment with lots of interplay with other members of their species as well as human companionship and tutelage. The research focuses primarily on symbolic communication studies. Our collaborators were psychologists Susan Savage-Rumbaugh, Duane Rumbaugh, and Rose Sevcik, as well as Kanzi, a 160-pound bonobo, often called a pygmy chimpanzee (Pan paniscus).
In the 1970s Australian archaeologist Richard Wright demonstrated that an orangutan (that lived in a zoo in Bristol, England) could be taught to make a stone flake and use it as a tool to cut through a cord to open a box containing food. This was a fascinating start, but the orangutan was not really faced with many of the problems and decisions that early tool makers had to contend with (how to hold and manipulate the core, how to search for angles, how to orient the core in relation to the hammer, where to flake next, and so on). The core in this early experiment had been preshaped with acute angles all around it and was strapped to a platform so that the ape just had to learn to hit an edge and remove the flake. Nor was this research envisioned as a long-term project to see how the ape might develop its tool making over time.
Using Wright's study as a foundation for further research, we wanted to look directly at behaviors analogous to what was going on in early tool making, to compare what Kanzi did and what he made with what early hominid tool makers were doing and making. Immediately we saw that Kanzi was going to be an excellent pupil. He was highly intelligent, focused in his studies, and resourceful.
The first day we started by showing him that stone tools are pretty useful things: a stone flake could be used to cut a cord and open a box containing a treat (of Kanzi's choice-a bunch of grapes, a piece of watermelon, a cold juice drink, and so forth). By the end of the first day Kanzi was using flakes that we had made and cutting readily into box after box, developing a true appreciation for stone tools. At the end of the second day he had become an excellent judge of stone knives: given a choice of five different pieces of stone to cut into his box, he could choose the sharpest one nine times out of ten. He was also making casual attempts to hit rocks together to make a tool on his own.
Kanzi is principally involved in communication studies, so he could only engage in these experiments from time to time, spaced apart sometimes by weeks. Within about a month of starting this study Kanzi was striking his first flakes off cores by hard-hammer percussion.
Since he was first initiated into the mysteries of stone tools, Kanzi has been given the latitude to develop his own flaking style, with occasional demonstrations to show how a modern human would do it. He was shown merely the fundamental principle of hard-hammer percussion-hitting one rock against another-as well as how useful these stone flakes can be. He immediately was interested in having these flakes to use, and this has become his motivation to try to make them himself. Over time Kanzi has been developing his tool-making skill and gradually getting more adept and precise at flaking stone. He was not conditioned or shaped in his flaking of stone. He is motivated by his desire to cut his way into his box and has been experimenting with rocks on his own to see how he can best get usable cutting tools from them.
Several months after the start of this study, Kanzi even devised his own technique for making flakes: purely on his own he developed the innovation of throwing his stones on a hard tile floor to fracture them and produce cutting edges. (Curiously, he had never been very interested in throwing until this technological advance of his, although some of his siblings have shown a penchant for throwing things. But now he seemed to find a purpose to it.) Within a few throws he usually was able to make a sharp flake, which he promptly used to get into his box. After this innovation he seemed to have made his own connection between the force of the throw and successful flaking. He now carried to look directly at behaviors analogous to what was going on in early tool making, to compare what Kanzi did and what he made with what early hominid tool makers were doing and making. Immediately we saw that Kanzi was going to be an excellent pupil. He was highly intelligent, focused in his studies, and resourceful.
The first day we started by showing him that stone tools are pretty useful things: a stone flake could be used to cut a cord and open a box containing a treat (of Kanzi's choice-a bunch of grapes, a piece of watermelon, a cold juice drink, and so forth). By the end of the first day Kanzi was using flakes that we had made and cutting readily into box after box, developing a true appreciation for stone tools. At the end of the second day he had become an excellent judge of stone knives: given a choice of five different pieces of stone to cut into his box, he could choose the sharpest one nine times out of ten. He was also making casual attempts to hit rocks together to make a tool on his own.
Kanzi is principally involved in communication studies, so he could only engage in these experiments from time to time, spaced apart sometimes by weeks. Within about a month of starting this study Kanzi was striking his first flakes off cores by hard-hammer percussion.
Since he was first initiated into the mysteries of stone tools, Kanzi has been given the latitude to develop his own flaking style, with occasional demonstrations to show how a modern human would do it. He was shown merely the fundamental principle of hard-hammer percussion this association to his hard-hammer percussion work, which before this time had been somewhat lackluster but now became much more forceful. Working outside again, without a hard floor to throw against, he became more proficient at hard-hammer percussion. Within about nine months of the start of this study he was removing several flakes from cores, producing objects that we can begin to compare with those in the early archaeological record.
Although Kanzi is still continuing to improve his tool-making abilities, his present level of expertise is significantly below that seen in Oldowan hominids. His core forms are strikingly similar to the natural eoliths produced by geological forces, which confused prehistorians around the turn of the century. He still doesn't show the understanding of flaking angles that Oldowan hominids had: Kanzi bashes and crunches the edges of cores with his hammer stone rather than using highly controlled and forceful blows that we can see in the early Stone Age artifacts. Recently, throwing has become his favorite technique.
We are enormously impressed with Kanzi's tool-making development and his innovations, and we're anxious to see how far he will take all this. Future questions we will ask include whether other apes at the laboratory might learn tool making from him and whether he will start to carry tools around for use at activity sites out in the research center's surrounding forest. (We are starting to put reward boxes outside in the woods, away from the rocks stored at the lab.) But despite his advances, the products he is now making are fascinating in their contrast with ones at early archaeological sites. This suggests to us that there may be an even earlier stage of stone technology in the archaeological record, perhaps rare and difficult for the archaeologist to identify. It will perhaps take a sharper eye and more time in the field to identify such sites, which would probably be earlier than 2.5 million years ago.
Moreover, Kanzi's progress so far as a tool maker suggests to us that early Oldowan hominids may exhibit a much greater cognitive understanding of the principles and mechanics of tool making than modern apes seem to be able to develop. This indicates something important about our hard-wiring, the size and complexity of our brain and its connections to the motor control system, at this stage in our evolution. We feel that these hominids probably had surpassed modern apes and probably their australopithecine ancestors in their ability to modify stones.
In addition to displaying enhanced skill, early hominids show a significant behavior in transporting stone, occasionally over distances of several miles and sometimes building great concentrations of artifacts and animal bones in certain places. Whether they did this all at one go or, more likely, in several trips, this suggests more foresight and planning with regard to carrying and collecting than is seen in nonhuman primates today. Chimpanzees in the wild rarely carry tools for more than one hundred yards or so, and they usually fashion a tool just prior to using it.
These early hominids, however, seem to be doing something quite different: they seem to have been planning and acting in greater anticipation of projected events and future needs.