But the carcass must be butchered now before other hungry scavengers arrive. The group can drive off jackals or vultures, but even with stones it is dangerous to try to hold off hungry lions, or hyenas, or a sabertooth.
Hippo hide is tough, but this is where experience pays off. The geologist quickly steps forward with his tool-kit. He takes out a palm-sized slicing tool, the edge carefully freshened up yesterday, and carves great long cuts into the hide. Willing hands grab the ends of the strips and tear them back, exposing fat and flesh. The geologist goes straight for the easiest and most desirable part, the liver, and hacks off chunks that are rapidly passed round the group. He does not pause to eat now, because the more skilful tasks are waiting. He goes now for the big joints, slicing tendons as hands seize and lever the limbs backward and forward. Soon large pieces are being passed out to people who decide how best to carry them. It's easier to carry when there's bone to grip, but the geologist can quickly slice a hand-hold into the tough hide. Strips of meat can have a hole punched through them so the children can carry them on sticks.
The geologist quickly gets into a bad mood. Hippos are really difficult. Thank goodness they don't come along too often. The carcass is so big that people expect too much, from the hippo and from him. The hide is really thick and tough, not of course as bad as a rhino, but worse than it looks: just those first dozen long cuts have taken the edge off his biggest slicer. The leg bones are thick and heavy and there's not much spare flesh around them, so there's a lot to carry for not much reward at the end. There's a lot of a hippo carcass that has to be left behind: it takes too long to cut and hammer at the massive pelvis, shoulders, skull, and ribs: the geologist wishes he had two wildebeest rather than one hippo: there would be just as much meat for less work.
Finally, everyone is loaded. In a more difficult season, the group might come back one more time to try to process scraps, but as it is, other carcasses will provide better pickings. The easiest pieces will be eaten today, and the rest will be sliced into strips and sun-dried.
The geologist looks to his tool kit that afternoon. The scrapers are smaller and have a more delicate edge than the big slicers and hammers: they take more time to re-sharpen, although they are smaller. He may have to send his apprentices off to collect more of the quartzite from the special site a few miles away.
Soon the usual routine will begin again. The scouts will go out patrolling for lucky finds like the hippo, but if they are not lucky they will have to be clever. They will visit the trees where the leopards cache their kills; they will check the favorite stalking grounds of the pair of sabertooths that are feeding their young in the cave along the ridge, or the lions that loll around most of the day under the acacias by the kopje. And then the tools will be needed, and the expert who can still use them best. He hopes the boys have been practising their stone-throwing. He doesn't relish the memory of the retreat at the end of the dry season, as they defended their scraps (and their lives) from the scrawny but dangerous group of hyenas that almost had them trapped in the blind ravine. As he gets older and slower, these encounters frighten him more.
That reminds him: he can have the apprentices practice their skills again tonight before he puts the final edges on their efforts. He must remind them again never to watch the impact edge as they rough-form it with the hammerstone. His useless eye aches again in the afternoon sun: one careless moment and one razor-sharp fragment when he was an apprentice. That's why there are scouts and collectors, and there are geologists: the former need keen long sight and stamina, and the latter need close-up vision and dexterity. There's not much call for an old slow hunter, he muses, but an old geologist still has skills that help the tribe. People can't eat anything bigger than a rabbit with fingernails and teeth: any big cat or hyena or vulture can do better than that. The tribe along the valley lost their geologist before he'd trained his apprentices: they enticed away his best pupil to fill the gap, which works well because the two groups must now share the same rock outcrop for tools, and there's even less friction than before...
Geologists made those early tools, and it is the interplay of geology and people through history that I shall follow in this book. Geology shaped the world of Homo habilis, and it continues to do so today in the world of Homo sapiens. It is not an accident that the latest formal war on Earth was waged in the Persian Gulf over the control of oil: a geological resource. As I write this, nasty little unofficial wars are being fought in Angola and Sierra Leone and the Congo (all of them over diamonds), and in Chechnya (over a vital strategic oil pipeline). Geology made the modern world possible, providing access to the resources, the fuels, and the water supplies that make our life so luxurious compared with that of our ancestors. But our dependence on geological resources also makes us vulnerable. Throughout history, the wise use of geological resources has been rewarded, but unwise use has been punished.
The tools fit the anatomy. Paleontologists argue that Australopithecus had huge jaws and teeth because it did a lot of chewing to process its vegetarian food: roots and fibers and leaves and nuts. Homo habilis chewed less because it had a significantly different diet and used tools to process its food before eating.
The tools of Homo habilis are deceptively primitive-looking. They were made by breaking and modifying pebbles and cobbles to leave a cutting or scraping edge exposed, or to form a simple hammer. There were no handles. These were all hand-held tools, yet they could be used for a great variety of tasks. The most important use for tools was food-processing: pounding and crushing roots and tubers, cracking nuts, and and above all, for butchering animals.
The scene in the prologue is not entirely imaginary. We have good archaeological evidence for much of it. About 1.8 million years ago in the Turkana basin, on the border of Kenya and Ethiopia, a group of Homo habilis cut up a hippo carcass on a gravel bank in a stream bed, leaving cut marks on the bones. They did not make their butchering tools on the spot, because the river gravel contained no pebbles. They must have carried the tools with them, or the stones to make them from, or they must have gone and fetched them from the nearest suitable rock outcrop. Given that the nearest suitable rock is at least 8 miles (14 km) away from the hippo site (at least a four-hour round trip) this suggests that Homo habilis routinely carried stones on foraging expeditions. It would only need a few minutes to get out the pre-selected stones from the carrying case (hide, probably), and make the tool kit.
Lighter carcasses might have been carried back to a base for butchering. At another stream bed site in the Turkana basin, tools are found along with over 2000 bones of game animals, most of them antelope.
The persistent presence of particular tool shapes suggests that they were deliberately made with a consistent technique. The tool maker had a picture in his mind of the finished product before he started to make it. The tools made by Homo habilis are so recognizable that they have been given a name, the Oldowan tool assemblage, after Olduvai Gorge where the Leakeys first recognized them.
We know how Oldowan tools were made, and we can guess how they were used, because of experiments by Nicholas Toth of Indiana University. Toth can make Oldowan tools by chipping flakes from a fist-sized stone. This leaves a "core" which may be a hammer and chopper, and "flakes" with sharp edges which may be knives and scrapers. The core may simply be the discarded piece from which the useful flakes were chipped, or the flakes may be the discarded debris that fell off as the hammers and choppers were shaped. Most likely, the primary aim was to make the smaller knives and scrapers.
We don't know whether Homo habilis was a hunter as well as a butcher, but it seems unlikely. None of the Oldowan tools could be used as a throwing or stabbing weapon. Most likely Homo habilis was an omnivorous scavenger, eating fruits, nuts, and seeds routinely, with meat from very small animals, or from carcasses of larger ones when they could be found. On the plains of Africa, well-adapted carnivores such as leopards, cheetahs, lions, hyenas and wild dogs hunted and killed game of all kinds very efficiently, as they still do. In addition, sabertooth cats the size of lions were major carnivores too. Predators like this rarely consume all the carcass right away; they usually eat much of the meat and leave the rest for scavengers. Leopards may cache the remains of the carcass in a tree, hoping to return to it. Partly consumed carcasses are a bonanza for efficient scavengers. Vultures and jackals are the most notorious of the African scavengers today, though lions, hyenas, and dogs will also scavenge the kills of others.
In the most evocative scenario for the biology of these early humans, Homo habilis was an omnivorous, opportunistic scavenger. Observant enough to spot the killing patterns of the local carnivores, crafty and mobile enough to find and carry away pieces, powerful enough to scare away at least the smaller scavengers, Homo habilis could harvest a rich new source of protein and calories, provided someone else ran it down and killed it. The only component lacking was the means to extract the most from every find. Unable to crack bones with its teeth like a hyena, unable to punch through hide or to tear off strips of meat with a sharp strong beak like a vulture, Homo habilis made the great breakthrough of using tools to do those jobs.
A pair of American anthropologists tried to find out how easy it would be to roam the African savanna in search of meat. They found that even as complete newcomers to the African bush, and newcomers to the idea of making their living as scavengers, they were able to get to know an area of several square miles in only a few weeks. They learned where the big cats roamed and often killed their prey, and they learned the favorite cache sites for leopard kills. They concluded that it would have been fairly easy for Homo habilis to have supplemented a diet of fruits and seeds with enough meat to make a great difference to dietary quality. A group of Homo habilis could have made a formidable show against all but the biggest cats, just as a troop of baboons today can defend itself, by noisy threats followed by stone-throwing if necessary.
But people can only make effective tools by selecting and carrying the right stones, and such skills are a matter of experience and training. The wrong kinds of rock will shatter, or cleave into thin plates, or will break too unevenly, or will not hold an edge. Only a rock that is hard but breaks reliably, isotropically (in any direction the tool-maker wishes), will make a good tool, and one must learn by experience what such a rock looks like, and where one can go to get a supply. Every animal knows by experience that essential items occur only in certain places (water, safe shelter at night, for example) and every animal knows at all times how far away those places are, and in which direction. At some level every individual Homo habilis must have been a geologist, or else there was a specialist geologist in every successful group. At some level, there must have been some sort of geological training that every young human received on the African savanna.
Every successful animal on the African savanna learns some basic biology and ecology. What was different about the new creature Homo habilis? I suggest that it was geology. The major breakthrough of these first humans was their effective exploitation of the geological resources around them. Geology has been a strong influence on human history ever since. The Gulf War (for control of the oilfields of Kuwait) is only the most recent example.
Obviously human history is multifaceted; but in this book I argue that the physical setting in which humans operate has greatly affected the decisions they have made. Humans have worked with the earth successfully, on the whole; but they have tried to work against it to their cost. The same laziness and greed that produced our technology have often led us to ignore the imperatives of earth science. And the lesson has still not been learned. Today, young humans preferentially learn mathematics, chemistry and physics in formal scientific training. That was certainly not the case two million years ago, and I would argue that we have lost a lot much by neglecting earth science (and biology and ecology) in modern education!
I am delighted to imagine that Homo habilis also invented laziness: that butchering tools were invented simply to make life easier, to avoid the damage and strain to teeth and fingers and the frustration that is involved in processing carcasses without tools. I suspect that Homo habilis was no fonder of hard work than I am. If we judge by later human history, laziness and greed, rather than necessity, are the mothers of invention. Tools are usually introduced to cut down on the time, effort, or cost of labor, or to make money or status for the inventor. They are not invented with the abstract altruistic vision that the new tool will make possible some entirely new way of life. The use of new inventions for entirely new purposes has usually been a secondary bonus. For example, the printing press was originally used to print Papal indulgences (the medieval European equivalent of paper money) faster than scribes could hand-produce them. Only later did the printing press revolutionize the way we educate, communicate, and bureaucrate (to coin an ugly new word).
We do not know much about the weaponry of Homo erectus, because only the stone tools have survived. We do know that erectus was much bigger than Homo habilis, allowing among other things more powerful throwing and/or thrusting action that would give better attacking capability and better self-defense. Somewhere around 1.4 million years ago, Homo erectus in Africa invented a new set of stone tools (Acheulean tools), and Nicholas Toth has made replicas of these as well. Acheulean tools are larger and better at both cutting and hammering than Oldowan tools, and it is probably not an accident that the sabertooth cats became extinct in Africa at this time, and the entire ecosystem of the African plains was reorganized.
I have written as if the success of our ancestors was an accomplishment driven by male expertise in tool-making and hunting. But no surviving "Stone-Age" society survives on hunting: all the members of the society participate in foraging and gathering, with meat as a welcome supplement. Even then, meat is available from animals of all sizes from insects and grubs to small game, fish, and then larger animals that require formidable weaponry to kill. The scavenging that is attributed to Homo habilis remains an important source of food too. It's probably a result of the fossil record that the hunting of Homo erectus is stressed so much: the butchering tools are so obvious at Homo erectus sites. The pounding, grinding, and scraping tools that would have been used (mostly by females?) to turn thousands of tons of grains, nuts, and fruits into edible ingredients, would have been just as numerous, but much simpler, and certainly more difficult to recognize and identify. The same blades and scrapers that are usually associated with stripping meat from hide would have been used to clean and cut fibers for a dozen "domestic" uses, as well as traps and nets for hunting small game, baskets for carrying fruits, nuts, and tubers, and cord for binding bundles of brush for the fire.
Stone tools and weapons, along with the bone and wooden artefacts that could be made with their aid, enabled Homo erectus to dominate the tropical plains ecosystem, and then migrate and dominate much of the Old World. Homo erectus, not the sabertooth cat or the lion, was now the most effective carnivore in Africa, South Asia, and southern Europe. Homo erectus was the first species of human to migrate out of Africa, and was the ancestor of Homo sapiens somewhere in the Old World.
Almost certainly, Homo erectus was the species that learned how to control fire. There is now good evidence of 1-million-year old campfires from a cave at Swartkrans, South Africa, associated with Homo erectus. This helps to confirm other evidence from archaeological sites scattered from France to China, each yielding Homo erectus remains and artefacts at sites that look like well-used hearths, all of them around 500,000 years old. These northern hemisphere sites in particular are in latitudes with cold winters, especially at times when ice advances brought tundra conditions to the plains and mountain areas of Eurasia.
It cannot have taken long for people to recognize that fire can be a profitable way of modifying the landscape. Grasses grow better after a fire, attracting game animals to the new forage. Fire can be used to scare animals, not just to keep away large predators, but to drive prey animals to a kill site. It is not clear at all when this kind of activity became widespread, but fire-sticks certainly arrived in Australia with the first wave of human immigrants, over 50,000 years ago. These were Homo sapiens, but their fire-control could have been perfected millenia before along the edges of the Southeast Asian rain forests.
I do not want to become bogged down in the controversy over the origin of modern humans‹whether it occurred in Africa, when it occurred, or whether the ancestors of modern humans spread over the Old World wiping out all their non-African counterparts, directly or by competition. Everyone agrees that the tool kits of early Homo sapiens are not dramatically different from those of Homo erectus, though they are naturally more varied and versatile, more sophisticated in their manufacture, and more effective in their uses. In the depths of the last Ice Age, modern humans, wherever and whenever they originated, occupied almost all the habitable areas of the Old World, from tropical rainforest to the fringes of the great ice caps, from Spain to Australia. About 12,000 years ago, people reached the last great uninhabited continental land mass, the Americas. By about 1000 years ago, people were living on every major land mass except Antarctica, and on almost every significant island. Only a very few places survived untouched until modern times: perhaps the best example are the Galápagos Islands with their amazing heritage of evolutionary wonders, unvisited by humans until 1535 AD.
I shall now turn from the realms of paleontology into the much richer evidence of the culture and history of modern humans, as gathered by archaeologists. Everyone agrees that thoroughly modern humans were widespread in the tropical and subtropical Old World around 50,000 years ago, with the possible exception of southern Europe, which was inhabited by Neanderthals. Neanderthals were most likely a separate group of specialized humans, but that's another controversy I don't want to explore here.
Around 50,000 years ago, some sort of Cultural Revolution among humans led to an explosion of art and artefacts, and a new level of sophistication in craft work. One can speculate about the reality of this change, its date, its causes if it is real, and its meaning for the evolution of the human brain and psyche, but from this point at least we can regard our ancestors as precisely like ourselves in anatomy and intelligence. We begin to see evidence of quintessentially modern social behavior: emblems of status and symbolism, personal property, the development of trade and the systematic exploitation of others, that may be expressed in simple artefacts and technologies but is either impressive or disturbing or both, depending on your mood at the moment. It's probably at this point in history that humans began to exploit the resources of the earth in a more intensive and systematic way.
Most rocks at the Earth's surface are sedimentary. They were formed by the accumulation of layers of sands, silts, and muds, and after they had been formed into rocks, they still break and split more easily along the layers than in any other direction. They are often too soft to make good tools, or may be made of such coarse material that they cannot be formed into smooth or sharp edges. Other rocks, igneous and metamorphic rocks, may also be layered, and are often granular in texture. Overall, rocks that are hard and isotropic are not rare, but they are not abundant either. The highest quality outcrops are rare enough, and yield material that is so much better than inferior outcrops, that they are considered valuable by the people in whose territory they happened to be.
The best material for making sharp tools is volcanic glass or obsidian; glass knives are sharper than steel when they are freshly made, and even today some surgeons will prefer to use glass knives for some procedures. Most volcanic rocks are lavas or ashes, and obsidian is comparatively rare. Often obsidian has too many bubbles in it, or it is found layers that are too thin to use effectively. But the right volcano (active, dormant, or extinct) can be a very rich source of excellent obsidian. The gifted people who make modern replicas of obsidian tools find it worth while to drive several hundred miles to load up with the best obsidian.
Flint is a close second to obsidian. Flint is a natural material formed in some sedimentary rocks. It is chemically similar to obsidian, in the sense that it is impure silica, or silicon dioxide. But it does not form from molten rocks as obsidian does. Instead, masses of flint are built up underground over tens of thousands of years inside a porous rock, as silica-rich ground water finds a situation in which it dumps the silica, often around a fragment of old organic matter. Flints often occur in irregular nodules along an old bedding plane in the rock, or along natural joints: if one finds one flint mass, one will likely find others by following along the structure of the rock outcrop. Flint, like obsidian, occurs in masses of different sizes and qualities. Here too, the most prized, high-quality flints are significantly rarer and more valuable than second-grade material. Chert is a variety of flint, and the names are sometimes used interchangeably. "Flint" is often used to designate high-quality chert that occurs in limestone rocks such as chalk.
Quartzite is a name for yet another rock type that is chemically impure silica. Here the rock itself is entirely made of sedimentary particles of quartz, formed, perhaps, on an ancient beach. Formed into rock, quartzite is granular because even in the rock, the original quartz grains retain their identity. But in the "best" quartzites for tool-making, the grains have partially fused together, much as ice grains partially fuse if you leave them in contact in the freezer. A quartzite made of very small quartz grains, well fused together, can make a serviceable tool. It will not give an edge quite as good as that of a flint, chert, or obsidian tool, but it will make just as good a hammer.
In the same way, any hard, uniform rock will make a serviceable hammer, or a crude axe. Greenstone is a "generic" name used by geologists to describe a metamorphic rock that is dark to light green in color, dense, with a chemistry that contains a significant amount of iron as well as silica. The most valuable and familiar version of greenstone is jade. It is isotropic, so it can be carved into intricate shapes, but it is also comparatively soft. Harder, less pure greenstone can be made into very servicable tools that are better at power hitting than delicate slicing and piercing. Greenstone axes and hammers have been made into tools on every inhabited continent. Perhaps the most famous are those from New Guinea and New Zealand, which were in everyday use for warfare and logging until they were replaced by steel tools after European traders arrived.
Apart from tools, there is strong evidence that ancient peoples valued some geological materials for their ornamental, or luxury, or religious value. For example, ochre is a red dye, made by pounding, crushing, and grinding the mineral hematite. Hematite is a fairly pure iron oxide, and occurs extensively though sporadically throughout the world, often along layers and joints in porous sedimentary rocks (it is deposited from iron-rich fluids in the same way flint and chert are, though they do not occur together). Hematite itself is a very dark color, metallic-black, and it is rather magical even to a beginning geology student to see that this mineral nevertheless produces a red powder. Ochre was a dye of great significance to ancient peoples.
The cave sites of Homo erectus at Choukoudien near Beijing, around 600,000 years old, yielded 20 clear quartz crystals, which do not occur in the local rock sequence. They must have been gathered for their beauty, because they are no good for any normal use. The tradition has lasted a long time: diamonds are notoriously showered on undeserving women by men with money to flaunt (Elizabeth Taylor had the good sense to turn Richard Burton's diamond into cold hard cash). Until very recently in New Guinea, utilitarian and ornamental stone axes were trade goods along with pretty shells and feathers. When Western objects entered the trade, they were the same mixture of utility and luxury: iron tools, mirrors, beads, and so on. As recently as the 1930s, the success of entire villages in remote areas in New Guinea rested on their possession of geological resources: the greenstone from which skilled craftsmen could make beautiful (and effective) axes. Often the axes were used in marriage-trading, which meant higher reproductive and social success for the inhabitants of the geologically favored villages: a particularly effective demonstration of natural selection in action!
It's certainly my prejudice that geological products (obsidian, flint, chert, greenstone axes and tools, ochre and other mineral pigments) would have been among the first goods and objects produced for trade. That is also what archaeological evidence says, although items such as these would also be very durable and likely to be preserved in the archaeological record. If we take the archaeological record on its face value, however, the geologists in early societies produced much of their trade "surplus." Don't laugh at this preposterous notion! The major export of many countries today is geological (see Table 1-1). But when did all this begin?
Here's an example from 12,000 years ago. Some of the earliest artefacts in continental North America are impressively long chert blades, made in what is now the state of Washington. They were crafted by the Clovis people had successfully by-passed the great ice sheets and arrived in the comparative Eden of unoccupied North America. The continent teemed with unwary game, nuts, fruits, and berries, with abundant salmon in season: and the Clovis people had a long tradition of big-game hunting in Siberia and Alaska. The Washington blades were made as exuberant masterpieces, for fun, or trade, or ornament, or prestige possessions, or generous gifts. Long slim chert blades are no good for practical purposes, as every Clovis person knew: they snap far too easily. These blades were pieces of extravagant art.
I like the concept that the earliest trading was not only geological, but was non-utilitarian: it was for art or magic (probably synonymous at the time) or for intergroup bonding (politics). Later, when we have much better evidence, we find also an important pattern of trade in "luxury" items along with utilitarian goods.
Let us now look at the way that human society was molded by the desire to gather goods for trading. When those goods were geological, that meant more effort had to be expended in making the earth yield ever-increasing geological resources.
Table 1-1 Modern Countries for which Geological Products are the Leading Export
Page last updated February 26, 2001.
Return to Geology 115 main page.
Return to Geology Department Web page