At Dmanisi itself, pollen studies indicate that just prior to its first occupation by hominids, southern Georgia had enjoyed a warm, damp climate supporting a rich mixed habitat of forested and grassy areas. But by the time the hominids actually appeared there a cooling and drying trend had begun to set in, expanding the areas of grassland and transforming the humid forests into formations of much more arid and crackly aspect. This is an environment that would have presented the hominids with a lower abundance of plant foods than their ancestors had benefited from back in Africa; but there is also evidence at Dmanisi of an extensive mammal fauna, including large herds of herbivores that the hominids must have exploited in some way—as bashed-in and cut-marked mammal bones confirm.
One new aspect of life that would have confronted the hominids arriving at Dmanisi is a pronounced seasonality in temperatures as well as in humidity; and this climatic variation would have deeply affected the resources available to them at different times of year. This was not an easy environmental transition to make, and it almost certainly could not have been managed by a typical primate species. This enhances our picture of the Dmanisi hominids as rugged, adaptable generalists, able to cope with rapidly fluctuating conditions. Evidently the key to early hominids’ success in Eurasia, then as now, was the unusual flexibility of behavior that had also been the hallmark of their African ancestors.
A particular surprise offered by Dmanisi came with the discovery of the fourth hominid skull to be recovered there. Known as D3444, this skull had belonged to an aged individual, thought to have been male, who was missing all but one of his teeth. It is not unusual to find fossil skulls that have lost their teeth subsequent to the death of their owner; but in the case of D3444 most of the missing dental elements had vanished long before his demise. Nearly all of his empty tooth sockets had already shriveled away, in a process that would have taken several years.
Front view of the toothless hominid skull from Dmanisi (D3444/D3900), about 1.8 million years old. This aged individual, presumed to have been male, had lost all of his teeth but one well before he died. It is thought that his survival may have required extensive help from other individuals, suggesting a social milieu of considerable complexity. Photograph of cast by Jennifer Steffey.
Especially if he and his kin had subsisted on a largely meat-based diet, this old male would have had great difficulty chewing his food; and the Dmanisi team believes that he would probably have starved without extensive help from other members of his social group (although he might conceivably have pounded meat with one of those rock cores to make it softer). Still, the argument that this highly disadvantaged individual had benefited from the long-term compassion of his relatives is, all in all, a plausible one: occasionally a chimpanzee manages to survive for a long period without teeth, but chimps eat a much softer diet than is probable for the Dmanisi hominids.
D3444 is by far the earliest example we have of an ancient hominid who somehow contrived to survive over a lengthy period with a major handicap. Indeed, the next oldest examples of disadvantaged individuals (these ones with evidence of cranial and brain deformities) are as much as a million years younger. That the aged Dmanisi male was capable of at least partly compensating for his physical disability by presumably cultural means has vague but powerful implications for cognitive complexity. What’s more, if the Dmanisi researchers are correct in their surmise, D3444 also furnishes us with the first putative instance of social concern in the hominid record. Evidence for human empathy of this kind only becomes abundant very much later in time; but, given the spotty nature of the earlier record, this is maybe hardly surprising. What’s more, compassionate behaviors are clearly as deeply ingrained in the human psyche as their opposites are; and it is even possible that we may glimpse the deep roots of such expressions in the consolation chimpanzees often offer to wounded or oppressed groupmates. What the apes most conspicuously lack, however, is the technical capacity to implement assistance; and it seems entirely reasonable to conclude that the Dmanisi hominids had the cognitive reserves to express their fellow-feeling in the form of material support. At the point when hominids first entered Eurasia they were evidently already beings of empathy, as well as of considerable resource and complexity.
MEANWHILE, BACK AT THE RANCH . . .
While hominids were busy spreading into other regions of the Old World, taking long-established ways of doing business with them, those that stayed behind in the parent continent were not standing still, at least technologically. As in Eurasia, the old ways continued—technologies have always overlapped in time, as they continue to do today—but at about 1.5 million years ago archaeologists in Africa (and recently in India, too) begin to pick up regular evidence of an entirely new concept in stone tool making. For a million years, and probably more, the key idea in making stone implements had been to produce a smallish flake with a usable sharp edge; and it hadn’t really mattered what those flakes, or the cores they were chipped from, had looked like. There was no aesthetic behind them; no notion even of basic form. The tool-making concept was totally a functional one: get that cutting edge.
Quite soon after Homo ergaster had come on the scene, however, all this changed dramatically with the appearance of what is known as “handaxes.” These stone tools are the emblem of what is known as the “Acheulean” culture, so-named for the site in France at which it was first recognized. Those handaxes are pretty late, however—they are dated to well under half a million years ago—and the earliest examples of this tool type are currently known from a site in Kenya dated to some 1.78 million years ago. At that remove in time, however, handaxes are rather crudely made and extremely rare. They did not become a routine feature at archaeological sites until several hundred thousand years later.
Handaxes are much larger tools than their predecessors, and involve an entirely new notion of what a tool was. To make a handaxe, a stone “core” (in later times, itself a large flake) was elaborately shaped by multiple blows to both sides into a flat, symmetrical teardrop form. They are typically about eight or nine inches long, but may occasionally be much larger. Sometimes these tools are quite pointed, in which case they are called “picks”; in other instances they may be truncated by a straight edge, and are known as “cleavers.” But the basic teardrop handaxe shape is quite uniform, and huge quantities of these implements were produced throughout the African continent and eventually beyond.
A “cleaver” (left) and a “handaxe” from St. Acheul, in France, from which the Acheulean industry was named. Photo by Willard Whitson.
The handaxe proved to be an extremely durable form: it was produced with little conceptual change, although with some later refinements in manufacturing, for well over a million years. Indeed, this implement has earned the sobriquet of “Swiss Army Knife of the Paleolithic” for its evidently many uses. Studies of how handaxes became worn in the course of such uses have shown that they were employed for tasks as diverse as cutting tree branches, slicing meat, and scraping hides. And the stability of the handaxe’s form indicates just how all-purpose these tools were, even as the habitats their makers occupied changed dramatically from moist to arid and back again, sometimes on incredibly short time scales.
Making Oldowan flakes had required a considerable sophistication in choosing the stone to be chipped: coarser-grained rock was less suitable for producing or holding that slicing edge. Volcanic glass, flints, and cherts, or even fine-grained lavas would do the trick, and these materials were assiduously chosen when possible. The earliest stone tool makers clearly knew good rock when they saw it, and as we’ve already seen they often carried it around for long distances in anticipation of needing it in places where none might be available. But the handaxe makers faced a yet more complicated situation than the Oldowans had. Not only did the rock have to be of the right kind, but the individual piece of rock had itself to be suitable, free of flaws that would foil the predictable flaking sequence needed to produce a shaped utensil. So not only did the toolm
aker need to be able to “see” the finished form in the rock before flaking started, but he or she needed to ensure that the core itself was sufficiently homogeneous to support the complex sequence of actions necessary. Clearly, this has profound if unclear implications for Acheulean mental abilities.
I’ve already mentioned that one of the most insuperable problems we have in our efforts to understand the cognitive background of any radical innovation such as handaxe making, is that we modern humans find it virtually impossible to imagine any state of consciousness other than our own. Even with the greatest effort of will we simply cannot put ourselves in the cognitive place of our predecessors, because the cognitive systems of those early hominids were clearly not simply scaled-down versions of ours. So we can’t get to where the early handaxe makers were by mentally ratcheting down our IQs a notch or three: and we will certainly be on the wrong track if we think that Acheulean tool makers were simply like us, but (because they had smaller brains) dumber. Indeed, if that had been the case they would almost certainly have had a very difficult time getting by. Doing business the way we do it demands the specific kind of smarts that we have; and our symbolic way of processing environmental stimuli seems to have been a remarkably recent acquisition. Without any doubt, the early handaxe makers’ subjective experience of the world, and their way of dealing with information coming in from it, were different in some major qualitative way from ours.
Limited as our speculations have to be, however, the conclusion is inescapable that the invention of the handaxe must have represented— or at least have reflected—a cognitive leap of some kind relative to the bipedal apes that had made the first stone tools. Making uniform objects according to a set of rules, as the handaxe makers did, implies obeisance to a collective appreciation of what is good and appropriate, and it has sometimes been considered to mark the boundary between “protohuman” and “human” behaviors. But just what did the cognitive change implied here mean in terms of what was actually going on in the heads of the hominids concerned? What did it reflect in terms of the way they apprehended and responded to the world? Unfortunately, there is nothing in the material record to suggest any answers.
Uncertainty as to what was going on is exacerbated by several other factors. For one thing, the invention of the handaxe seems to have taken place after Homo ergaster appeared. This is actually not surprising because, as I remarked in chapter 6, the technological advances that provide our best clues to cognition at this stage must have been made within a hominid species, if for no better reason than there was nowhere else for them to occur. Clearly, the intellectual potential for envisioning that a specific, realizable teardrop form lay within a lump of stone must have been present in the physical brains of the handaxe makers before they started expressing it. Still, the identity of the inventors of this new technology remains a bit hazy, if only because of the probability that there is more than one distinct species among the spectrum of hominid fossils generally allocated to Homo ergaster (let alone to the all-embracing Homo erectus); and, if so, we have no idea of who was doing what. The current state of our knowledge merely allows us to be certain that a spirit of innovation was astir among early Homo in the African continent beginning well over 1.7 million years ago. And this is quite probably the most important thing to know, especially since there is no evidence that more than one hominid grade was involved in the process of technological advancement.
Whatever the details of the transition, exactly how the fulfillment of the neural potential underwriting the invention of the handaxe affected other aspects of the Acheuleans’ lives remains anyone’s guess. For although a lot of handaxe sites are known, the kinds of activities performed at them seem, at least early on, not to have been hugely different in material terms from those documented at older sites. There is one major exception to this, though. Previous toolmakers had typically made their stone artifacts at butchery places, as and when they were needed. Tools at such places are not usually found in great abundance because of the small quantities of stone that the makers could reasonably carry around for flaking on the spot. In contrast, handaxes were often made in huge quantities, at “workshop” localities, often in close proximity to good sources of appropriate rock. Perhaps the most famous such place is at Olorgesailie, in Kenya, where literally thousands of million-year-old stone tools were found littered in a small area of the ancient landscape. This concentration of tools implies an entirely different approach to life than had been taken by the Oldowan tool makers, including the earliest Homo ergaster. It even strongly suggests that some degree of specialization in social and economic roles existed among members of the group.
The suggestion has also been made, though it is quite controversial, that the sites containing unusual quantities of handaxes hint at ritual gatherings, and at a social rather than purely utilitarian function for at least some of these tools. This remains pure speculation; but it is possible to draw this conclusion with more confidence from the spectacularly large size of some of the handaxes found at places like Isimila, in Tanzania. These tools were far too big and heavy to have been used for routine chores, and they have invited speculation that their uses were instead ceremonial. And while this inference may be a little too loaded with implications of our own style of humanity, it is quite possible that such tools were made in a playful spirit, or perhaps even a competitive one of showing off at large social gatherings. Expressions like these make it all the more frustrating that we have so little other supporting evidence about Acheulean lifestyles—which may well have become more complex with the passage of time: Isimila is quite late.
At Olorgesailie we also have the best current physical candidate for an actual maker of early handaxes. Not far away from the rich tool site, at the same stratigraphic level, were found fossil bits of a very small individual—far more diminutive than the Turkana Boy—who the excavators of the site suspect may have been a member of the population to which the toolmakers belonged. They described the specimen as a Homo erectus, but in truth this is much more because of its date than its morphology. The cranial fragments look nothing like the type specimen from Java, or, for that matter, the Boy. Still, under current standards it is entirely reasonable to attribute it to an early member of the genus Homo; and while a guesstimate places its brain size at under 800 cc, this lowish figure is nonetheless within the Homo erectus/Homo ergaster range, especially considering the individual’s petite size.
BRAINS AND BRAIN SIZES
With Homo ergaster and Homo erectus we confront for the first time an episode of marked brain-size enlargement among the hominids, and this issue is a uniquely important one to confront. The brain sizes of fossil hominids have attracted a huge amount of attention, not simply because our large brains have for long been our most vaunted organs (at least as they distinguish us from other animals), but also because brain volume is easy to quantify as long as you have a fossil cranial vault that is sufficiently well-preserved to measure, or from which to make an estimate. One fascinating thing about hominid brain sizes over the last couple of million years is that, without any doubt, they show a striking trend toward enlargement with time. Brain sizes had more or less flatlined during the long tenure of the australopiths. The very latest australopiths seem on balance to have had slightly larger brains than the earliest ones; but even if this doesn’t simply reflect body size, the difference is too small to be worth noting. But once the genus Homo was on the scene, everything changed. On average, the later in time a fossil member of the genus Homo is, the larger its brain is likely to be. This really is important, because the way we process information in our heads most clearly demarcates us modern humans from all other creatures on the planet; and our cognitive abilities are certainly dependent on our large brains, even if size is not in itself the whole story.
So brain size is without doubt a critical factor in human evolution. But we have to be careful how we interpret it. Particularly under the gradualist dictates of the Evolutionary Synthesis, paleoanthr
opologists have often been tempted to simply join the dots into a single continuum of brain size increase. Two million years ago, our ancestors’ brains were basically ape-sized; a million years later, they had doubled in volume; and today they are twice as large again. What could be more suggestive of an inexorable trend, as smarter individuals out-reproduced dumber ones? And what, looking back, could be a greater compliment to our current finely burnished species? When you think about it, this really is the ultimate paleoanthropological feel-good formula.
But there are other ways to look at the brain size picture. For a start, even though we don’t have anything like the number of fossil hominid braincases we’d like, we do have enough to know that at any one point in time brain sizes varied widely. Among the australopiths, we’re in the fairly tight range of about 400 cc to 550 cc. Among the earliest species of Homo, in the period following about two million years ago we’re looking at a range of some 600 cc to 850 cc; and by around half a million years, give or take, the range has broadened to around 725 cc to 1,200 cc.
We are also looking at a pretty impressive if often unacknowledged variety of morphologies. Take, for example, four eastern African crania, all dated to roughly one million years ago: that tiny individual from Olorgesailie (reckoned to have had a brain capacity of less than 800 cc); a cranium from Buia in Ethiopia (750–800 cc); a skullcap from Daka in Ethiopia (995 cc); and a braincase from Bed II at Olduvai Gorge (1,067 cc). All have been allocated to the species Homo erectus; but all of them look decidedly different, not only from the Javan type specimen of the species, but from each other. There is clearly more going on here than a simple lump categorization as Homo erectus or even Homo ergaster can reflect, for none of them looks much like the Turkana Boy, either.
Masters of the Planet Page 16