(Pages 187-199)
While Glynn Isaac was beginning to re-examine his interpretation of early Homo behavior, Lewis Binford was sharpening his pencils in preparation for a vigorous foray into African archeology. Binford, an archeologist at Southern Methodist University in Dallas, is as noted for forcing archeologists to examine their methods of analysis and interpretation as he is for the acerbic tone of his critical attack. For instance, he suggested that researchers who interpreted early archeological assemblages in Africa as ancient living sites were "making up 'just-so' stories about our hominid past." It is an attention-capturing approach, but it irritated some scholars. It irritated me.
For a long time archeologists had more or less assumed that early Homo lived like modern hunter-gatherers, or at least a primitive version of that life. They assumed that when they found bones and stones associated in the archeological record, they were looking at the remains of hunter-gatherer campsites, which just happened to be 1.5 million or more years old. I'm convinced that Glynn was scientifically correct when he said we had to stand back from the process and try to sort out assumptions from valid interpretations. Site 50, which was to be part of that reexamination, to some degree got caught up in what is best described as the campaigning zeal that Binford created. Glynn, in his attempt to strip his interpretations of all unwarranted assumptions and speak only from direct inference, became too cautious .
Binford was skeptical of his colleagues' conclusions about ancient living sites because of his own experience with the record of Neanderthals, members of the human family who lived in Eurasia between about 135,000 and 35,000 years ago. He compared evidence of their way of life with that of modern hunter-gatherers. What he thought he saw obviously impressed him. "The more I learned about hunting and characteristic archeological signatures for typically human ways of life, the more I was convinced that ancient human beings - the Neanderthals-had been very different from us," he said. "If this was true, then the cozy picture of very early hominids painted by Leakey and Isaac for a much earlier time period appeared to be paradoxical."
If Neanderthals were as unskilled and unorganized in their subsistence strategies as Binford supposed, it is little wonder that he had difficulty in accepting that, almost two million years earlier, early Homo had already developed the rudiments of the hunting-and-gathering way of life. For Binford, the hunting-and-gathering mode is a recent development in human history. "Between 100,000 and 35,000 years ago the faint glimmerings of a hunting way of life appear," he concluded. "Our species had arrived -not as a result of gradual, progressive processes but explosively in a relatively short period of time." Binford posited that this late, explosive arrival of people like us was the result of the sudden invention of spoken language. My position is very different.
The life of hunter-gatherers has fascinated anthropologists for more than a century, and in recent decades fine studies have been conducted on some of the rapidly dwindling number of foraging peoples. Not surprisingly, some aspects of the hunting-and-gathering life differ from one people to another, particularly when the environment is different. It would be unusual if, for instance, the Eskimos of the frozen north were to organize their lives identically with the San people of the Kalahari Desert. Nevertheless, some general patterns emerge, and these patterns imply a kind of inner coherence to the social and economic demands of hunting and gathering.
For instance, hunter-gatherers typically make a camp, or home base, in one location for several days, perhaps a week or two. They forage in the surrounding area, collecting the available plant foods and getting meat in any way they can. Then, when the resources begin to thin out, they move on to another location. There is a constant monitoring and exploitation of resources, with frequent moves to new areas. A campsite is rarely used more than once unless it is particularly rich in resources, such as the marine resources enjoyed by the Indians of the northwest coast.
Early Homo erectus bands must have used their landscape in many different ways too, so that one would not expect all archeological assemblages of bones and stones to be the litter of identically organized ancient home bases. But surely some of these assemblages represent home bases.
Not so, according to Binford. "The famous Olduvai sites are not living floors," he concluded in his book Bones: Ancient Men and Modern Myths.. Not one of them. "The only clear picture obtained is that of hominids scavenging the kills and death sites of other predator-scavengers for abandoned anatomical parts of low food utility, primarily for purposes of extracting bone marrow," he said. Hence his characterization of proto-humans as "marginal scroungers." Archeological assemblages, according to Binford, were the result of proto-humans taking stones to abandoned carnivore kill sites, where they smashed a few marrow-bearing ones and then went on their way. Not a very human image.
And image is important, in science as in many endeavors, perhaps especially so in anthropology. Image affects the way in which evidence is interpreted in this case, whether in the early archeological record we are seeing remnants of the activity of creatures that were humanlike or were far removed from humanity. To describe early Homo including Homo erectus as being "marginal scroungers" is to exclude them from other aspects of humanity. But if our ancestors were hunters of some skill, who lived complex social lives, then the consideration of other aspects of humanity
One focus of research in this context for Glynn and his associates inevitably lingered on the bones at archeological assemblages. Assuming, as good evidence suggests, that hominids actually transported the bones to the sites, one asks whether the animals had been hunted or scavenged. When a hunter kills an animal, he may take back to camp whatever part of the carcass he desires. A scavenger is usually second in line to the carcass, and he can take only what the initial predator hasn't already eaten. The choice of body parts is therefore more limited for the scavenger. The patterns of bone assemblages at the home bases of hominid hunters and hominid scavengers would consequently are different. That's the theory.
"In practice it's very difficult to discriminate between a pattern that results from hunting and a pattern from scavenging," says Rick. It is sometimes impossible. "If a scavenger finds the carcass of an animal that has just died of natural causes, then all the body parts are available to the scavenger, and the bone pattern that results will look just like hunting. And if a scavenger manages to drive a predator off its kill very early, the pattern will again look like hunting. What are you to do?" It's a tough challenge, one that may elude all attempts to solve it. The Chicago anthropologist Richard Klein, one of the most experienced and thoughtful archeologists in the matter of bones assemblages, is not optimistic:
There are, however, tantalizing insights, such as that provided by one of the most unusual discoveries in this whole episode. For decades people had been talking about hominids as meat eaters and had analyzed the stones and bones collected from supposed home bases. Everyone assumed that the hominids had used the sharp stone implements to butcher carcasses. But no one had seen any direct evidence of the activity, such as the trace of a sharp edge on soft bone. Such cut marks can be seen in bony litter left behind by modern hunter-gatherers, whether they use blades of steel or of stone. But there was nothing in the archeological record.
Then, in the summer of 1979, cut marks were discovered independently by three different researchers, all within a few months of one another. It was one of those remarkable coincidences in research, as if the right time had arrived for something new to be found. Rick Potts found cut marks. So did Pat Shipman. And so too did Henry Bunn, a member of Glynn's team.
The marks appeared as short grooves, with a V-shaped cross-section, cut into the surface of fossil bone, from Olduvai and from Koobi Fora, preserving the activity of early Pleistocene butchers. Sometimes the cut marks were near the ends of bones, produced, presumably, when the proto-hominids were dismembering a carcass. Sometimes the cut marks were on parts of bones where only skin and tendons could be had. "For the first time, there was a firm link between stone tools and at least some of the early fossil bones," said Pat, eliciting a collective sigh of relief from the archeological community. It was an important discovery, because, given the minimalist mental approach of some researchers, unless a direct causal link could be established between bones and stones, interpretations of archeological assemblages would be based on mere assumptions. I was delighted, but not surprised, to see the hard evidence of ancient butchery.
Even more evocative was the discovery that on some of the cut-marked bones were grooves left by carnivore teeth. Sometimes these ancient signatures overlapped, a cut mark crossing a gnaw mark, a gnaw mark crossing a cut mark. "When you see a cut mark on top of a gnaw mark, you can be sure you're looking at hominid scavenging," observed Pat. The carnivore clearly got to the bone before the hominid butcher. "Unfortunately, when you see gnaw mark over a cut mark, it's equivocal. The hominid may have killed the animal. But, then, the animal may have been dead when the hominid came along and butchered bits of it. Then a carnivore came along and had a gnaw at it. You just can't know for sure."
In the presence of this ambiguity, what can we say about carnivory in general that may be helpful? First, there are very few pure predators, like the cheetah, or pure scavengers, like the vulture. Most carnivores scavenge when they can and hunt when they must. I see no reason that our ancestors, when they became meat eaters, did not fit this pattern. I know from experience how
easy it is to get meat as a hunter, and one doesn't have to be lethally armed to do it. Very effective are traps and snares, made from branches bound with bark strips, all of which would be invisible in the archeological record. As a boy I used to make crude traps of this sort. They are simple to construct and efficacious. I would be surprised if this kind of thing did not go back far into our history, probably beginning with the expansion of the brain in Homo.
What do we see when Homo comes along? We see a rapid expansion in brain capacity, and this must equate in crude ways with increased intelligence, which, among other things, would have enhanced technical skills. Even chimpanzees are successful at organized, cooperative hunts
But we see something else in early Homo, something that could well enhance our understanding of the life of these ancestors. It concerns the shape of the body, and derives from two different researchers with very different perspectives.
"We were sent a cast of the Lucy skeleton, and I was asked to assemble it for display," remembers Peter Schmid, a paleontologist at the Anthropological Institute in Zurich. For people interested in ape and human anatomy, the institute is a center of great renown. There, during the 1940s and 1950s, Adolf Schultz built up one of the world's best collections of ape skeletons. Schultz's work provided a foundation on which much of contemporary comparative anatomy is built, and his institute welcomes a constant stream of researchers who need to understand ape anatomy. "When I started to put the skeleton together, I expected it to look human," Schmid continues. "Everyone had talked about Lucy as being very modern, very human, so I was surprised by what I saw."
The chest was the problem. "I noticed that the ribs were more round in cross-section, more like what you see in apes," he explains. "Human ribs are flatter in cross-section. But the shape of the rib cage itself was the biggest surprise of all. The human rib cage is barrel-shaped, and I just couldn't get Lucy's ribs to fit this kind of shape. But I could get them to make a conical-shaped rib cage, like what you see in apes."
We know that Lucy had unusually long arms and relatively short legs, but the assumption was that, because she was bipedal, her body was like that of modern humans. After the experience with the rib cage, Peter decided he would look further into the anatomy of the entire upper body. He examined the whole trunk, the lumbar region, and the shoulders. He wanted to know how Lucy
The shoulders, the trunk, and the waist are important in human running the shoulders for arm swinging and balance; the trunk for balance and breathing; and the waist for flexibility and swinging of the hips. "What you see in Australopithecus is not what you'd want in an efficient bipedal running animal," says Peter. "The shoulders were high, and, combined with the funnel-shaped chest, would have made arm swinging improbable in the human sense. It wouldn't have been able to lift its thorax for the kind of deep breathing that we do when we run. The abdomen was potbellied, and there was no waist, so that would have restricted the flexibility that's essential to human running." In other words, Lucy and other australopithecines were bipeds, but they weren't humans, at least in their ability to run.
While Peter Schmid was working with the Lucy skeleton in Zurich, Leslie Aiello was crunching numbers at University College, London. One set of numbers she was working with was the weights and heights of the San Francisco 49ers offensive line. "I needed data on some big, I mean really big, humans," she explains. They don't come much bigger than that. Most of her data were more conventional, however the heights and weights of modern apes, and estimates of heights and weights of various hominid specimens, including Lucy.
She found a striking pattern. By comparison with humans, apes are heavily built for their stature. For instance, a six-foot-tall chimpanzee might be twice as heavy as the average modern human of the same height. Leslie was asking how our ancestors fitted into this comparison. "No doubt about it," she states. "Australopithecines are like apes, and the Homo group are like humans. Something major occurred when Homo evolved, and it wasn't just in the brain."
Perhaps because we've been dazzled by the spectacular size of the human brain
By having less bulk for their height compared with apes, humans have a greater relative surface area over which to lose heat. The long lower limbs give us an increased stride length, and the lower positioning of the center of gravity (in the pelvis rather than in the thorax) reduces inertia, or drag, when we walk or run. Leslie suggests that these features would be important to a bipedal hominid engaged in increased activity in a warm, open environment.
This conclusion conjures up images of humanness rather than apeness, and it derives from basic studies of anatomy, not from unrestrained fantasy. That is important. Just as these insights were being developed, a third pertinent idea was emerging, thanks in part to a trip to an auto mechanic and a chance letter from a colleague. Dean Falk, an anthropologist at the State university of New York at Albany, has studied the inside of fossil hominid crania for almost two decades, and is exquisitely familiar with the information to be gleaned from them. One thing she learned was that blood vessels that drained the brains of hominids fall into two patterns. In the earliest known hominids and most of the australopithecines, the blood flows in a few major vessels at the back of the brain and then into the jugular veins. Homo is different. The blood flows through a much broader network of veins, a pattern that becomes more elaborate through evolutionary time. This difference eventually led Dean to propose her so-called radiator theory.
Dean's conversation with her auto mechanic, Walter Anwander, a whiz who completely rebuilt her 1970 car, sowed the seeds of the theory. "One day, while he was enumerating the wonders beneath the hood," recalls Dean, "Walter pointed to the radiator and said, 'The engine can only be as big as that can cool.'" Hominids are machines of sorts too, and cooling is important, particularly for the brain. Not long after Walter Anwander's instructive observation, Dean published some of her results on cranial vessels in hominids. Michel Cabanac, a French physiologist, saw Dean's scientific report and wrote to her, pointing out that heat dispersal would become especially important as brain size increased in human history. Perhaps the drainage patterns Dean had discovered were pertinent to this.
Indeed, thought Dean, and she soon proposed the idea that the broad network of drainage veins in early Homo brains would have permitted strenuous, heat-producing activity. Not so in the early australopithecines. How to test the theory is difficult, if not impossible, to imagine. Nevertheless, it is at least consistent with the inferences drawn from body structure in australopithecines and Homo, and consistency is sometimes all one can hope for in scientific theories, particularly those dealing with historical events.
I was delighted when I heard on the grapevine about these ideas, and about Leslie Aiello's and Peter Schmid's results. It seemed to me that here was an angle that would catch the archeologists by surprise. Early Homo looks to me like a creature adapted to broadening its diet by becoming partly carnivorous in a physically active manner. It could run like us when it needed to; and it had tremendous stamina, like us. These are the marks of human hunters. Australopithecines had neither characteristic. They were not hunters. But what of the notion that, as carnivores, proto-humans operated from temporary home bases, that a humanlike social and intellectual milieu was already emerging? We've seen that the period of childhood in Homo erectus must have been extended because of the immaturity of the infant's brain at birth. Is Site 50 an example of such a home base, or merely a conglomeration of bones and stones of little anthropological interest, as Binford has suggested?
The three years of patient work at the site paid off, yielding interconnected data of a quality and comprehensiveness never before achieved at an early archeological site. In the end, Glynn and his associates were able to demonstrate that the meat-bearing bones at the site had been transported there, almost certainly by the proto-humans themselves. Some of the bones bore the telltale cut marks; others had been broken open with hammerstones. The stone tools had actually been made on the site by one or more of the Homo erectus band. We know this because Ellen Kroll was able partly to reassemble some of the pebbles from which flakes had been struck. And in a clever microscopic investigation, Larry Keeley, of the University of Illinois, and Nick Toth, of Indiana University, were able to show that some of the stone flakes bore signs of use on meat, tough grass, and wood.
These various insights transform our image
Glynn was more cautious. Site 50 did demonstrate what he suspected hominids of this era transported stones and bones to a chosen spot and used stone tools to get meat. But he stopped calling such places "home bases" and instead referred to "central place foraging." He said at a conference to commemorate the hundredth anniversary of Darwin's death "My guess now is that, in various ways, the behavior system was less human than I originally envisaged." Glynn, I believe, was being too cautious, too much influenced by that pendulum. He said, "It is my strong suspicion that if we had these hominids alive today, we would put them in zoos, not in academies."
I am not suggesting that the Turkana boy was as human as we are today. But I challenge the notion that humanness arose very rapidly and very late in our evolution. I suspect that this extreme position has been adopted because of a desire to have ideas accepted in an unusual intellectual climate, an unconscious but powerful process. Many people believe that humans are so different from the rest of the animal world, they cannot accept the idea that we are a product of evolution, just like other species. Perhaps some anthropologists react to this unscientific position by emphasizing the special human qualities when they offer scientific explanations of our origins.
Much more reasonable, it seems to me, and much more consistent with the evidence, is the notion that qualities as complex as consciousness, morality, and ethics developed over a long period of time in our history. I believe that the Turkana boy lived in a rich social milieu, elements of which we would recognize as being human. And I speculate that when the Turkana boy died, his kin would have felt and shared emotions of grief much more like those which humans experience today than those which chimpanzees experience....
(Page 169)
We can be sure, however, that Homo was a tool maker, because once Homo species were the only hominids around, tool making continued. I recognize that this is argument by exclusion. I recognize too that chimpanzees can use tools, such as stones to crack open nuts. But there is a great conceptual leap from using stones as simple hammers with which to break things to using stones to strike a flake off another stone. The brains of australopithecines were not significantly bigger than those of modern great apes, including chimpanzees, taking body size into account. The brains of earliest Homo were significantly bigger, and that extra brain power must mean something.
The more parsimonious position is to suggest that stone tool making was the province only of Homo, from the earliest times in the record through to the end. Proving it one way or the other may never be possible. Those involved in the quest for human origins have to accept that some questions, no matter how germane, may never be answered.
One of the questions arises from the evidence that while Homo was opening up a new hominid niche, other hominids began to slip into evolutionary oblivion they became extinct. Of the three or more species of hominid that existed between 2 million and 2.5 million years ago, only two made it through to a million years ago Homo erectus and the robust australopithecine. And of these two, only one persisted beyond a million years ago. What can we say about this, beyond recording that it happened? Not much, and nothing for certain. But our intense curiosity about our ancestors forces us to wonder.