Read Shadows of Forgotten Ancestors Online
Authors: Carl Sagan,Ann Druyan
Over the course of human history, some religions, it is true, have become much more than this—at their best transcending intimidation, hierarchy, and bureaucracy, while providing comfort for the powerless. A few, rare, religious teachers have acted as a conscience for our species, have inspired millions by the example of their lives, have helped us to break out of baboonish lockstep. But none of this contradicts the thesis that a generalized religious predisposition, ready to be put to use by the local social structure, may be a commonplace in the kingdom of the animals.
Perhaps, if we were able to peer into the mind of the ape in a state
of nature, we would find—among a flurry of other feelings—a sense of satisfaction about its apeness rivaling ours about our humanity. Every species may feel something similar. It would be far more adaptive than its opposite. If anything like this is true, then we would be denied even our self-congratulatory distinction of being the only animal that makes self-congratulatory distinctions.
If we have not much peered into the hearts and minds of other species and have not even studied them carefully, we may impute to them virtues and strengths as well as vices and deficiencies that in fact they lack. Consider this bit of verse by the poet Walt Whitman:
I think I could turn and live with animals, they’re so placid and self-contain’d,
I stand and look at them long and long.
They do not sweat and whine about their condition,
They do not lie awake in the dark and weep for their sins,
They do not make me sick discussing their duty to God,
Not one is dissatisfied, not one is demented with the mania of owning things,
Not one kneels to another, nor to his kind that lived thousands of years ago,
Not one is respectable or unhappy over the whole earth
On the basis of the evidence presented in this book, we doubt if any of Whitman’s six purported differences between other animals and humans is true—at least given a little poetic license; that is, in the spirit if not the letter of the poem. Montaigne thought
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that when we conclude that other animals have “ambition, jealousy, envy, revenge, superstition, and despair,” we are simply projecting our own “sickly qualities” onto the beasts; but this goes too far, as the lives of the chimps make clear. While many commentators have exaggerated the differences between humans and “animals” and warned of anthropomorphizing, others, like Whitman and Montaigne, have romanticized and sentimentalized the animals. Both excesses serve to deny our kinship.
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The proximate cause of human success must have something to do with the conjoining of our intelligence and our talent for making and using tools. Surely, our globe-girdling civilization arises chiefly from these two abilities. Without them, we would be nearly defenseless. But “a little dose … of judgment or reason often comes into play, even in animals very low in the scale of nature,” Darwin wrote in
The Origin
. Late in life, he made extensive studies of what you might think is an unpromising subject, the intelligence of earthworms. He gave them intelligence tests involving the manipulation of real and artificial leaves. They did very well. Flatworms can work their way through a simple maze to get a reward; even worms have a degree of intelligence. Galapagos woodpecker finches, studied by Darwin on the voyage of the
Beagle
, use twigs to worry wood-dwelling larvae out of branches; even birds have a rudimentary technology.
Certainly we could not have invented civilization without intelligence and technology. But it would be unfair to describe civilization as the determining characteristic of our species, or as establishing the level of intelligence and manual dexterity required for our definition, especially because the first 99 percent of the tenure of humans on Earth was spent in an uncivilized state. We were humans then, as now, but we hadn’t dreamed up civilization. Yet the fossil remains of the earliest known humans and hominids—dating back not just hundreds of thousands but millions of years—are often accompanied by stone tools. We had the talents, at least in partial measure. We just hadn’t gotten around to civilization yet.
The contrast between the proclivity for tools in humans and the absence of tool use in so many other animals has made it tempting to define ourselves as the tool-using or the tool-making animal—as seems to have first been suggested by one of the members of Josiah Wedgwood’s and Erasmus Darwin’s Lunar Society, Benjamin Franklin. On April 7, 1778, James Boswell confesses to admiring Franklin’s definition. The ever-grumpy and sometimes over-literal Samuel Johnson objects: “But many a man never made a tool; and suppose a man without arms, he could not make a tool.” Again, if we are to define a human being, should we use traits that, without exception, every human being possesses, or traits that may be present only potentially? And if the latter, who knows what traits lie smoldering in other animals, not yet fully elicited by circumstance or necessity?
——
Blasé, matter-of-fact, encumbered by the infant (who, face to her chest, clutches her fur), she carefully positions the hard-shelled fruit on the log and smashes it open—using a stone tool procured for the purpose. Hammer and anvil. No light bulb goes off above her head. There’s no chin to fist, no hint of insight struggling to emerge, no moment of revelation, no strains from Also
Sprach Zarathustra
. It’s just another routine, humdrum thing that chimps do. Only humans, who know where tools can lead, find it remarkable.
Although many chimps literally do not know enough to come in out of the rain, they’re able to use tools. Not only that: they’re able to
premeditate
the use of tools—to acquire a tool now for some action they intend to perform later. They go large distances to find the right kind of stone or stick, and then lug it home. They seem to have had its ultimate use in mind all the while.
“It has often been said,” wrote Darwin in
The Descent of Man
, “that no animal uses any tool; but the chimpanzee in a state of nature cracks a native fruit, somewhat like a walnut, with a stone.” His source was that acute but easily offended Victorian observer of chimps, Thomas Savage, M.D. Chimpanzees regularly crack open hard-shell seeds and nuts with a stone hammer against a stone or wooden anvil; and they’ll carry the appropriate rocks over a good fraction of a kilometer for the purpose. At other times, wooden clubs may be used as nutcrackers. In the Tai Forest in the Ivory Coast, chimps select an appropriate club, climb a cola tree, pick the choice cola nuts, and crack them open using the branch as the anvil and the club as the hammer.
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Female chimps are more likely to employ hammer-and-anvil technology than males, and they’re better at it.
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A chimp breaks off a long grass stalk or a reed so she may use it later, hundreds of meters away, more than an hour in the future, to lure delectable termites out of a log or termite mound. She must remove superfluous leaves and twigs, shape it, shorten it, insert it into the termite tunnel with a deft twisting motion to follow the interior contours, shake it seductively to attract termites onto it, and then with great care remove it without scraping off too many. Chimps take years to perfect their technique and routinely teach it to their young, who are avid pupils. This exactly satisfies one confident definition of “the uniqueness of man’s toolmaking”—namely, “the fashioning, out of natural materials, of an implement designed to be used at a distant time and on objects not now perceptually present.”
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How difficult is chimpanzee termite fishing? What depth of intellect and manual dexterity are required? Suppose you are dropped naked into the Gombe Preserve in Tanzania and, like it or not, discover that termites are your principal hedge against malnutrition or starvation. You know they’re an excellent source of protein; you know that self-respecting humans in many parts of the world regularly eat them. You manage to put aside whatever compunctions you may feel. But catching them one at a time is not going to be worth the effort. Unless you’re lucky enough to encounter them when they’re swarming, you’re going to have to make a tool, repeatedly insert it into their meter-high mound, introduce the tool into your mouth, and strip off the clinging termites with your teeth and lips as you withdraw the tool from your mouth. Could you do as well as a chimp?
The anthropologist Geza Teleki tried to find out. He spent months in Gombe under the tutelage of a chimp named Leakey, who was adept at the technique. Teleki wrote about his findings in a famous scientific paper called “Chimpanzee Subsistence Technology.”
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The Gombe termites mainly come out at night; before dawn they expertly wall up all the entrances to their mounds. Chimps routinely begin their termite foraging by scraping away these entrance barriers. Teleki’s inquiry started there:
Having repeatedly observed [chimpanzee] individuals approach a mound, make a rapid visual scan of the surface while standing on or beside it, and reach decisively out—with a high degree of predictive accuracy—to uncover a tunnel, I was soon impressed by the apparent
ease with which tunnels could be located. In attempting to learn the technique, I applied several experimental procedures: examining in minute detail all crack patterns, protuberances, depressions and other “topographic” features in the clay. But, after weeks of futile searching for the essential clue, I had to resort to scraping mound surfaces with a jackknife until a tunnel was inadvertently exposed. My inability to find any physical features which could serve as visual clues eventually led me to realize that chimpanzees may possess knowledge far beyond my expectations.
. . The only hypothesis which, at this point, seems to reasonably account for the observed facts is that an adult chimpanzee may know (memorize?) the precise location of 100 or more tunnels in the most familiar mounds. Moreover, since intensive probing is restricted to a short annual season, the possibility that chimpanzees retain a mental map of core mound features during the intervening 10 months must also be considered. That chimpanzees require a prolonged learning period (i.e. 4–5 years) to gain proficiency in this technique …, and that some individuals are known to have the capability to retain specific information for many years, provides circumstantial support for this hypothesis.
Next, Teleki looked into a selection of raw materials for the manufacture of the termite probe:
When performed by experienced chimpanzees, the selection procedure seems deceptively simple. After a brief visual scan of the nearby vegetation, a chimpanzee will usually extend a hand and deftly tear off a twig, vine or grass stalk. Sometimes the individual must move a few paces away from the mound and fetch a suitable probe, and in some cases 2–3 objects are initially selected. These may be rapidly examined and discarded until some specification is met in one, or several may be carried to the mound for subsequent selection. Whenever it occurs, the selection is made in a swift, almost casual manner, and modification is begun if necessary. Without being aware of the nuances involved, it is easy to undervalue the proficiency needed to perform these maneuvers.
Chimpanzees presumably have the experience whereby the properties of an object can be evaluated before it is applied to the task of probing, for the rate of error in selecting probes is not high … When probing for termites, the specifications are in fact surprisingly
stringent: if the vine or grass selected is too pliant, it will buckle and collapse (accordion-like) when inserted into a twisting tunnel; if, on the other hand, the object is too stiff or brittle, it will catch on the tunnel walls and either break or resist entry to the necessary depth …
Despite months of observing and aping adult chimpanzees as they selected probes with enviable ease, speed and accuracy, I was unable to achieve their level of competence. Similar ineptness can only be observed in chimpanzees below the age of about 4–5 years.
Finally, putting aside the difficulties in finding the tunnel entrances and manufacturing the tools, Teleki set himself to learning how to use a competently produced tool:
I spent many hours inserting probes, pausing for the designated interval, and pulling them out again—without getting any termites. Only after some weeks of nearly total failure … did I finally begin to grasp the problems involved …
In order to collect these subterranean termites, the probing object must first be carefully and dextrously inserted to a depth of about 8–16 cm [centimeters], with appropriate turns of the wrist so that the object navigates the twisting channel. The probe must then be gently vibrated with the fingers during the prescribed pause, for without this movement the termites may not be stimulated into biting firmly onto the probe. However, if the vibration is performed too lengthily or roughly, there is an excellent chance that the probe will be cut through by the [termites’] mandibles while still in the tunnel. When these preliminary actions have been correctly performed, the probe, presumably with dozens of termites now attached, must be extracted from the tunnel. Once again there are nuances to be observed. If the object is too rapidly or clumsily pulled out, the insects are likely to be scraped off along the sides of the tunnel, which then yields nothing but a shredded probe. The hand motions must be reasonably but not overly swift and, once started, uniformly fluid and graceful. If the tunnel is particularly tortuous (a feature which can be determined during insertion of the probe), the success of the catch can be ensured by a slow twisting of the wrist while the probe is pulled out.
It is a little daunting to discover—on the very technological grounds on which human superiority is often claimed—that after months of
apprenticeship, human scientists cannot do as well as preadolescent chimps. Teleki remained generous and good-natured about his failure. In the acknowledgments at the end of the paper, among thanks to various organizations for financial and logistical support, there appears this sentence: “I am, in addition, more than grateful to the patient and tolerant Leakey, whose termite-collecting skills so outstripped mine.”