Kanzi: The Ape at the Brink of the Human Mind (43 page)

At the Wenner-Gren conference several people felt uncomfortable with Kanzi’s command of language comprehension. They were able to take satisfaction, however, when I acknowledged that it would probably be more difficult to teach Kanzi to tap dance than to use a keyboard-based language system. Their relief was because they felt that there might be a link between the highly developed motor skill that we use to tap dance and the similar motor-planning routines required by speech. Moreover, the idea of increased motor skill and planning as an evolutionary engine interested those, such as Patricia Greenfield, who saw evolutionary links between the development of tool-use skills and language—and suggests a common neurological substrate for both.

Evidence for the putative neurological link between tool-use
skills and language includes the fact that certain brain areas, such as the inferior parietal association area, are involved in both object manipulation and language; in this case, object naming and grammar. This kind of overlap is clearly seen in certain patients who have suffered damage to their Broca’s area. Depending on the nature of the damage, such people may be unable to construct grammatical sentences. In other words, they are unable to assemble words in a hierarchical manner. These same people are unable to sketch out simple hierarchical patterns, using short sticks and a model to copy. In experiments with young children, Patricia tracked the emergence of the hierarchical concept with age. She asked the children to copy a symmetrical model, again building a two-dimensional structure using short sticks. Although children aged seven and older built the structure along hierarchical lines, younger children did it piecemeal, focusing on one local area of the structure at a time.

The implication of this and other evidence is that, rather than arising in neurological isolation, as the Chomskian position argues, language abilities are intimately related early in life to abilities of object manipulation. “The ontogenesis of a tool-use program relies on Broca’s area in the left hemisphere of the brain, just as early word formation does,” observes Patricia. “This is the key point in relation to tools and language: they have a common neural substrate in their early ontogenetic development. . . . These programs differentiate from age two on, when Broca’s area establishes differentiated circuits with the anterior prefrontal cortex.”
⁴

If this is indeed the case, then it is legitimate for archeologists to look for evidence of linguistic abilities encrypted in stone-tool assemblages. Changes in the cognitive sophistication of tool assemblages should—in some way—also reflect changes in linguistic capacity. The problem is, there is no objective method for assessing the degree of cognitive sophistication embodied in mute stones, as I learned from the disagreements voiced among the archeologists present at the Wenner-Gren conference in Portugal. When, almost two decades ago, Glynn Isaac tackled the challenge of looking for signs of language in tool technology, he first looked at the overall picture between
two and a half million years ago and a little more than thirty thousand years ago. This perspective on the trajectory of language evolution through the past two and a half million years led him to rather different conclusions from those derived from the anatomical evidence produced by the reconstruction of vocal tracts and observations of brain expansion and organization. Isaac concluded that the initial stage of stone-tool technology, the Oldowan, produced between two and a half and one and a half million years ago, implied “designing and symbolizing capabilities . . . not necessarily vastly beyond that of contemporary [apes].”
⁵

Tom Wynn and Nick Toth have looked at the same evidence more recently, with somewhat different results. As I indicated in
Chapter 8
, Tom believes the Oldowan tool technology was essentially within the cognitive reach of an ape. “In its general features Oldowan culture was ape, not human,” he concluded. “Nowhere in this picture need we posit elements such as language. . . .”
⁶
Nick, on the other hand, states that the “Oldowan tool makers were not just bipedal chimpanzees.”
⁷
Nick bases his conclusions on the fact that the earliest tool-makers apparently had mastered the principles of concoidal fracture, that is, the searching out of appropriate angles for striking platforms and the delivering of appropriately angled blows with a hammerstone. This mastery, says Nick, implies a cognitive competence beyond that of apes, and may be taken as evidence of some linguistic ability.

Nick has other evidence of the earliest tool-makers that, he ventures, might again point to linguistic abilities. Specifically, he discovered that in the earliest archeological sites in Kenya, the tools were all made by right-handed individuals. This fact was revealed by the position of pebble cortex on the flakes. Because right-handers hold the core in their left hand and rotate it clockwise, the cortex, when present, will mostly be on the right edge of the flake. The opposite is true for left-handers. Although individual apes and other primates often have a handedness preference for manipulative tasks, as a species they are equally divided between right-handers and left-handers. Humans are unusual in having a population preference for one
hand—90 percent of humans are right-handed. Handedness is associated with localization of function to the opposite brain hemisphere. The location of manipulative skills in the left hemispheres of (most) right-handers is accompanied by the location there of language skills, too. The right hemisphere has become specialized for spatial skills.

If it is true that language and manipulative skills evolved together, it seems likely that brain lateralization was part of that process. In that case, perhaps the Oldowan tool-makers, being preferentially right-handed, could have increased linguistic skills after all? The asymmetry of brain function is accompanied in modern humans by an asymmetry of shape: The left hemisphere is emphasized. This same asymmetry is seen in the earliest known crania of
Homo habilis
, the putative first tool-maker, but not in any austraiopithecine species. Nick sees this as further evidence of linguistic abilities in the Oldowan tool-makers.

Despite their differences of interpretation over the Oldowan evidence, Nick and Tom agree over the general significance of the next stage, the Acheulian. Unlike the simple core tools of the Oldowan, which may be formed by the removal of a very few flakes, the Acheulian handaxe involves extensive flaking and about fifteen minutes of effort. “Besides manifesting a clearer sense of spatial geometry [than in Oldowan tools], the technical sophistication of [handaxes] is such that even modern humans learning to make stone tools often require many months of apprenticeship to reach the requisite level of finesse,” observes Nick.
⁸
This is evidence for cultural norms, he suggests, and a greater language ability than in the Oldowan tool-makers.

Tom sees “something humanlike in this product of
Homo erectus
minds,”
⁹
referring to the handaxe. “Artifacts such as these indicate that the shape of the final product
was
a concern of the knapper and that we can use this intention as a tiny window into the mind of
Homo erectus”
¹⁰

These three lines of anatomical evidence—of the brain, the vocal apparatus, and the capacity for tool-use—provide the principal support for the notion of long, gradual changes on the road to language. Along with these changes in the brain and the vocal apparatus, there occurred concomitant gradual changes in
the hand, changes that made it an increasingly suitable instrument for tool construction and use. As we saw in
Chapter 8
, Kanzi has difficulty flaking and using stone tools because of his elongated fingers, which cannot be fully straightened, his inflexible wrist, and his short and highly positioned thumb. While he can see how we hold the cobble and the hammerstone, and he can attempt to imitate our grip, he can never position the stones as effectively as we can for flaking.

Nonetheless, the coincident changes in the anatomy of the hand and wrist, and the increasing signs of tool construction and use in the fossil record have led many scholars to conclude that a common neurological structure undergirds both skills and that this structure is to be found only in
Homo
. To say that a common neurological substrate may exist still does not explain the nature of the driving force that was pressing brain expansion at such an unprecedented rate in all of mammalian development. Yes,
Homo habilis
was making simple tools and
Australopithecus
probably was not, but did
Homo habilis
require a brain that was 50 percent again larger than that of
Australopithecus?
Given Kanzi’s ability to flake stone, the answer obviously seems to be no. What then was pushing the brain to become larger?

It may be that actually making a tool is far simpler than having the foresight to know that a tool would be necessary in the future. Making a tool entails a great deal more than simply bashing stone together. In order to make a tool, one must have the right sort of stone at hand and one must not be engaged in another activity. In Kanzi’s case, these conditions are provided; we bring the rock and we focus his attention on the need for a tool by baiting the tool site. However, we were not around to help out
Homo habilis
. He had to plan ahead. He had to know that at some future time he would need a tool, even though he did not need it for a specific task at the time he found the proper stone or at the time he actually constructed the tool. Thus, the real cognitive demands placed on any tool-user entail finding the proper material, making the tool, and keeping the tool with him or her until it is needed. And all of this must happen without a stimulus, that is, without some immediately present
set of circumstances that make the need for a tool manifest. If a tool-maker recognized that he needed a tool only when the occasion actually arose, it is likely that (1) there would be no appropriate stone around, and (2) by the time he made the tool, the situation leading to its need would have changed.

Consequently, it is not simply an understanding of geometry that a tool-maker must have; first and foremost the tool-maker must have the ability and the intelligence to plan ahead, to disjoin present behavior from future need. For this, the tool-maker must construct an elaborate mental model of the anticipated future. This model must include the tool and its purpose as well as the tool’s shape and the actions required to produce that shape. Once the tool is made, the maker must keep the tool in his or her possession until it is needed. This may seem simple, but when there are streams to be crossed, berries to be picked, predators to avoid, children to watch, and when the tool must be on hand at night as well, keeping this tool at ready access is not a trivial task. Only to the extent of anticipating future need, in the absence of any current reminder, will a hominid go to the trouble of carrying and keeping a single tool. Keeping a kit of such stone implements becomes even more difficult. Indeed, once the stone tool kit becomes larger than two or three implements, it is easy to see why temporary home bases, scattered throughout a range, would become necessary and convenient for storage.

Many animals, including apes, sea otters, and birds, use tools—but only apes and man make tools, and only man makes tools that he is not going to use in the immediate future. In addition, man carries tools long distances for days or weeks anticipating their future use. Man keeps tools with him, through daylight and darkness, through bad weather and good. Unlike other animals, man searches far and wide for good raw material from which to make his tools and then transports that material to other locations. All of these skills require considerable foresight and planning, skills attributed to the frontal lobes. They require constant orientation to the future and a clear understanding that present and future needs may not be the same. The greater the ability to plan ahead, anticipate future needs, and prepare for them,
the greater the chance of survival for a creature who has small teeth and minimal means of natural defense.