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The Pre-human Bipeds and their Environment

Three million years ago, there were primates which we now call australopithecines. The australopithecines had brains no bigger than chimpanzees, they were shorter than us, with very long arms, quite probably (though we do not know) they were covered in fur, but they were bipedal, as we are. We have even discovered their footprints and they look like human footprints. But the australopithecines were not humans. They may have been different in many ways from chimpanzees, but they were almost certainly even more different from us. They have taught us that bipedality has not always been synonymous with humanity.

The australopithecines were one of nature's success stories. We are now finding more and more of their remains, in all the parts of sub-Saharan Africa which have been seriously excavated. They diversified into at least two species, including a relatively heavyweight animal with very powerful jaw muscles, adapted to eating tough vegetation and a "gracile", more lightweight species.

Bipedalism and the Canine Teeth

Various as they were, all the australopithecines appear to have differed from their primate predecessors in two ways. They walked on two legs; and their canine teeth became progressively smaller.

Animals must be prepared to defend themselves and (particularly) their young against predators. Nature therefore typically provides them with weapons. Male mammals often have particularly well-developed weapons, which they also use in competing for females and territory; but females too are usually armed for defence against predators (see link). Most mammals which lack horns or antlers rely mainly on biting. They often have canine teeth specially adapted for use as weapons (this even applies to some deer which lack antlers - see link). Quadrupedal primates (including chimpanzees) typically have well-developed canines.

But bipedal primates, including the australopithecines, our Homo predecessors and ourselves, do not have canine weapons. We no longer defend ourselves with our teeth.

In some of the earliest australopithecine fossils, the canines are still bigger than the other teeth, though smaller and less impressive than those of a chimpanzee. In the later australopithecine fossils, the canines take their place, as ours do, as food-processing tools rather than weapons.. The picture below, taken from Glenn Conroy's Reconstructing Human Origins, shows (left) the teeth of Proconsul, an earlier fossil ape, (centre) the teeth of Australopithecus afarensis (about 3.3 million years ago) and (right) Australopithecus africanus (about 2.6 mya):

The reduction in the size of the canines would not have surprised Darwin:

The free use of the arms and hands, partly the cause and partly the result of man's erect position, appears to have led in an indirect manner to other modifications of structure. The early male forefathers of man were, as previously stated, probably furnished with great canine teeth; but as they gradually acquired the habit of using stones, clubs, or other weapons, for fighting with their enemies or rivals, they would use their jaws less and less.

(Darwin: The Descent of Man)

Was Darwin right? Chimpanzees do not rely entirely upon their teeth when fighting: they also use sticks and throw stones. There is a remarkable Youtube video clip (see link) which shows chimpanzees attacking an artificial leopard with sticks. Other sources also confirm that chimpanzees often throw sticks and stones, but tend to suggest that they are not very good at it. The forelimbs of a chimpanzee are general purpose organs, adapted for locomotion - and needed for locomotion whenever the animal wants to move quickly and nimbly. A habitual quadruped is likely to be slow and liable to lose its balance when fighting on the back legs alone. And chimpanzees appear always to throw underarm - a very weak and ineffective method compared with the human throwing action.

But the australopithecines, although related to chimpanzees, were bipeds, perhaps as quick on their two feet as an active modern man. They had hands and arms which (not being required for locomotion on the ground) could afford to specialise in manipulation - throwing and handling weapons and tools. They probably became better at throwing stones; they would have been better able to carry a supply of stones around with them, and they would have been better at fighting at close quarters with clubs. As bipeds, able to keep predators at a safe distance much of the time with missiles and clubs, they perhaps had less and less need to bite or threaten their enemies with their teeth. It was more useful for the canines to be adapted for eating.

Many other suggestions have been made as to the reasons for the evolutionary success of bipedal apes. But it is becoming increasingly clear that Darwin was right: bipedalism made it possible for the australopithecines to "use stones, clubs and other weapons" instead of fighting with their teeth.

Darwin's suggestion has received conclusive support from a detailed and convincing study of the human hand by the distinguished anatomist Professor Richard W Young:

It has been proposed that the hominid lineage began when a group of chimpanzee-like apes began to throw rocks and swing clubs at adversaries, and that this behaviour yielded reproductive advantages for millions of years, driving natural selection for improved throwing and clubbing prowess. This assertion leads to the prediction that the human hand should be adapted for throwing and clubbing, a topic that is explored in the following report. It is shown that the two fundamental human handgrips, first identified by J. R. Napier, and named by him the ‘precision grip’ and ‘power grip’, represent a throwing grip and a clubbing grip, thereby providing an evolutionary explanation for the two unique grips, and the extensive anatomical remodelling of the hand that made them possible. These results are supported by palaeoanthropological evidence.

(Evolution of the human hand: the role of throwing and clubbing - see link for full text of paper)

Unlike australopithecine and human hands, chimpanzee hands lack a strong opposable thumb:

The grips of the chimpanzee differ profoundly from those of humans (Napier, 1960). For suspension from horizontal supports, chimpanzees use a ‘hook grip’ of the four flexed fingers (Napier, 1960; Marzke & Wullstein, 1996). With vertical supports, a diagonal hook grip is used (Susman, 1979; Marzke et al. 1992). The thumb may touch the support, but does not squeeze it against the palm. Chimpanzees use this grip when flailing with sticks, but when the arm swings forward the hand tends to lose its grip, possibly due to weakness of the thumb and its inability to overlap the index finger (Marzke et al. 1992; Marzke & Wullstein, 1996). Because the thumb is weak and short, its distal phalanx is relatively immobile and its distal pad cannot be opposed to those of the fingers, it cannot generate a firm pinch or squeeze (Marzke, 1992a, 1997; Marzke & Wullstein, 1996). (Young)

It is worth looking again at the Youtube video. Notice how the attacking chimpanzee loses his grip on the stick at the moment of impact and leaves it behind - partly perhaps because his grasp is not firm and flexible enough to withstand the shock of impact and partly because he wants to make use of all four limbs to ensure a rapid retreat. In fact he does not make a clear distinction between a missile and a hand-held weapon which is retained to repeat the blow.

Building on earlier research by Napier and Marszke, Professor Young demonstrates that surviving fossils of australopithecine hand bones show from the beginning a decline in specialisation for tree climbing and a new specialisation for throwing and clubbing, with the throwing and clubbing adaptation improving in the later fossils. These later fossils correspond to those in which the canine teeth become less well adapted to use as weapons.

An important paper by Barbara Isaac (see link) anticipated Professor Young's conclusion:

Ability to throw was probably achieved at an early stage of human evolution but has received little scholarly attention. Although this ability is poorly developed in apes, anatomical studies suggest that the hand of Australopithecus afarensis was adapted to throw with precision and force.

Mrs Isaac's paper pointed out nearly twenty years ago that

A cornered band of protohominids armed with rocks weighing 200g would be formidable opponents. All carnivores avoid disablement which can lead to starvation....the use of stones would usually be defensive, occasionally aggressive, and subsequently predatory.

There is no evidence that australopithecines made artificial stone weapons But unworked stones, well chosen, make very good missiles anyway. The ability to throw stones (and to carry around with them a stock of suitable natural ammunition) must have given these bipeds a competitive advantage which no other animal had. They could drive away their enemies by inflicting injury at a distance whilst remaining out of range of hostile and predatory teeth and claws.

From the beginning, bipeds probably became expert at throwing stones. A shower of stones can kill any animal which cannot run away (people have been executed by stoning) and well-aimed sharp stones might well drive away a leopard or a lion. Against an animal which can run away, the value of stoning is primarily defensive; but in conflict with a predator, defensive action is all that is required. Predators are careful to avoid injuries because even a minor injury can diminish their chances of killing prey and can rapidly lead to starvation. Stones - or better still, sharpened stones - can be an effective defence, in the right hands, against predators.

The human throwing action is a complex one (see link), in which great power and accuracy are achieved by the coordination of all the muscles of the arm, wrist, fingers and back - even of the legs. We do not know whether the australopithecines could throw missiles as well as we can. But if, as it seems, the ability to throw missiles effectively was a fundamental factor in bipedal survival, then the evolution of those muscles (and of the brain which controlled them) must have been influenced by the need to develop that ability. Bipeds are perhaps (among many other things) animals evolutionarily designed to survive by throwing missiles.

The evidence suggests that the long struggle for bipedal survival and ultimately human dominance over all other species began when the australopithecines differentiated themselves as animals which walked, ran and fought on their back legs only, and could use their hands and arms to wield weapons and to throw missiles, thus uniquely becoming able to drive away predators and competitors whilst avoiding combat at close quarters.

Animals in the wild have learned from hundreds of thousands of years of experience of us and of our bipedal predecessors that our missiles - first stones, later spears, arrows and bullets - can kill or maim quite unexpectedly from a distance without harm to ourselves. They have learned that even to be seen, at a distance, by a biped, can be dangerous or even fatal. It is best to keep out of our way, at least during daylight. That is why we can often walk through a wood which is full of wild animals of all kinds and yet hear and see almost nothing. Modern animals have learned the need to keep out of our way and have passed the knowledge on genetically or by example to their offspring. Those who failed to learn this essential lesson have left no descendants.

The australopithecines were certainly not people, by any reckoning. They were bipedal apes. But in one respect at least they were a step in the direction of people. Unlike other animals, people have learned to transcend the limitations of their own bodies. What we cannot achieve with our own bodily apparatus, we have learned to achieve with the aid of external tools, equipment and weapons. Without wings, we have nevertheless learned to fly. Without sharp teeth, horns or hooves, both we and the australopithecines learned to defend ourselves with missiles and to keep our enemies at a distance. The stone missiles of those bipedal apes were the first step in the direction of the more sophisticated missiles of the twenty-first century. And the long story of pre-human and human development which started with those bipedal apes - a story in which we bipeds gradually became complete masters of our environment (if not of ourselves) - began with them.

Bipedalism and Brain Size

Among placental mammals, only australopithecines and members of the genus Homo are bipedal. But bipedalism is not unusual among other species; in the past it has been much more common than it is now. Many if not most dinosaurs were bipedal; all birds are bipedal, including flightless birds, notably the ostrich, which is a very fast runner and holds its own among the great quadrupedal mammalian predators of Africa. Marsupial mammals are at least partially bipedal. The reason why they differ in this respect from placental mammals may be that marsupial infants are very small at the time of birth, and marsupial mothers do not need a wide birth canal.

The story of brain development is also the story of the development of the pelvis. When the australopithecines adopted the upright posture, the pelvis changed, to allow for the new centre of gravity of the body and for the necessary bone and muscle modifications required for walking vertically on the back legs alone.

But the pelvis is also a girdle through which the infant head must pass. The picture above, taken from the Cambridge Encyclopedia of Human Evolution (M H Day, P88), shows (left) the pelvis of a female chimpanzee, (centre) that of "Lucy" - a fossil australopithecine - and (right) that of a modern woman. In each case, the infant's head is shown emerging at the time of birth. It shows how relatively more difficult it was for the infant australopithecine's head to pass through his mother's pelvic girdle. The change in pelvis shape needed for upright walking, running and self-defence had made it difficult to give birth to a big-headed child. In the australopithecines, brain size was of the same order as in chimpanzees. Any increase in brain and therefore infant head size would have made births even more difficult.

Lucy's bigger-brained successors (of the new genus Homo) probably evolved two solutions to this problem. One was for the infant to be born at an earlier and more helpless stage of foetal development, when the head was smaller. Jennifer Worth, in her autobiographical Call the Midwife, comments on this:

The helplessness of the newborn human infant has always made an impression on me. All other animals have a certain amount of autonomy at birth. Many animals , within an hour or two of birth, are up on their feet and running. Others, at the very least, can find the nipple and suck. But the human baby can't even do that. If the nipple or teat is not actually placed in the baby's mouth and sucking encouraged, the baby would die of starvation. I have a theory that all human babies are born prematurely. Given the human life span - three score years and ten - to be comparable with other animals of the similar longevity, human gestation should be about two years. But the human head is so large at two that no woman could deliver it. So our babies are born prematurely, in a state of utter helplessness.

Jennifer Worth: Call the Midwife

The other solution to the problem was a modification in the shape of the female pelvis, allowing for the need for a wider birth canal, but at the expense of bipedal speed and agility. This modification must have had implications for walking, running, fighting and climbing trees. Reduced female speed and agility might have meant a greater dependence on the protection of the male. In most other animals, females (whilst often not as aggressive as males) are well able to defend themselves against predators. By contrast, human females have historically tended to depend on male protection at times of physical danger. Perhaps greater brain size may have been balanced by a progressive tendency for the infant to need more protection from the parents and the mother more from the father.

And unlike other animals, hominid mothers (like modern women) may now have had difficult births, for which they needed a midwife (see link) Thus they were also more dependent on the older, more experienced females of their group.

Fire

The australopithecines retained relatively long arms and were probably still partial tree-dwellers; like all modern primates (except fully-grown male gorillas, who are too heavy and have little to fear) they are likely to have retired to the trees at night. This applies also to the habilines, who may represent an intermediate form between australopithecines and true Homo. But around 1.8 million years ago appeared Homo erectus, the early African examples of which are often called Homo ergaster. Homo erectus/ergaster had limbs and body shape much more like our own, although brain size was initially only about about 800 cc compared with a modern volume of 1200 to 1500 cc. Over the following million or more years, brain size seems to have gradually increased.

The bipeds we call Homo erectus lived in more open country and expanded from Africa into drier and colder regions in southern Eurasia. They cannot always have depended upon trees as refuges at night. On the ground they would have been at the mercy of nocturnal predators with good night vision and/or much better senses of smell and hearing. Did they have fire? At the time, fire was probably an even more important advance than flint-working, but it leaves much less trace in the archaeological record and we do not know when it first came into general use.

The effects of the regular use of fire would have been extremely dramatic (see link). Fire illuminated and scared away predators at night and provided warmth in a cold climate. And above all, cooking would have revolutionised eating patterns. Uncooked food demands continuous chewing; it uses up calories to chew and to digest and it may yield fewer calories in the end, because digestion is often only partial, especially of foods to which the digestive system is not well adapted. Chimpanzees spend most of their waking hours gathering food and eating it as they gather; other herbivores in general follow a similar pattern. Australopithecines and habilines probably did the same. By contrast, humans typically cook their food and eat it in family groups at the end of the day. That way, they gain more calories and are able to eat a much wider range of foods. Apart from throwing and language, the use of fire is undoubtedly the most important innovation which distinguishes bipeds from other animals.

At some time within the last two million years, bipeds started to habitually make use of fire. Of course it might not always have been possible to light a fire anew every evening, especially in cold and damp conditions, when fire was most needed. The ability to make fire at will, which we take for granted, cannot be assumed even in the more recent prehistoric past. Settled agricultural communities later kept fire going continuously in a communal hearth (often invested with religious significance, as in the Roman temple of Vesta). But pre-agriculturalists must move around to follow up available resources; and recent hunter-gatherer peoples often carried fire around with them - even sometimes (in Australia) in canoes. Fire-carrying is possible, but it must be difficult to combine with other activities - whether food gathering or defence against predators and territorial enemies. Perhaps it suggests that bipeds who used fire either tended to return to a base-camp at night (see link) or moved around in fairly big groups, so that they could afford to depute the role of fire-carrier to one individual - perhaps an older male - who was relieved of other responsibilities.

Stone Implements

From about 2.5 million years ago, the first stone implements have been found. Suitable types of stone were shaped into implements, the actual purposes of which are not always clear. Unfortunately, this discussion has been made difficult by an apparent general agreement among palaeontologists to disregard entirely the need for defence against predators. This is despite the fact that all the hominid fossils of this period are of teeth, bones and bone fragments originally scattered by predators and scavengers. Despite this evidence and much discussion of tools and diet, weaponry for defence is hardly ever mentioned.

For more than a million years, the commonest stone artifact was the so-called "hand axe:"

A hand axe was a large stone chipped into an almond shape, with a sharp edge not only at the point, but also all round, so that it would have been awkward to use as a hand-held cutting tool. Although this idea has not yet gained general acceptance, it seems increasingly probable that what we call "hand axes" were actually missiles (see link).

Over the immensely long period during which hand axes were produced - a period of more than a million years, during which the hominid brain almost doubled in size - the art of making and throwing missiles is likely to have been gradually perfected. The pre-sapiens period of hominid development culminated with the Neanderthals. If a Neanderthal (with the benefit of training or example based on literally hundreds of thousands of years of practice) could throw a sharpened stone missile reliably to hit a distant target point first - and he probably could - it would have been a very dangerous weapon.

Over the million years of handaxe development, the hominids undoubtedly made themselves increasingly formidable opponents whom it had become dangerous for most other animals - apart from the very largest and most thick-skinned - to approach too closely. But to actually kill or disable a large animal, a stone point needs to gain momentum and penetration by being hafted on to a wooden shaft. No such hafted spear points or arrow heads appear until some time in the last 100,000 years (see link). Apart from stones and sharpened stone missiles, what other weapons were available? Wooden clubs and sharpened wooden spears are useful defensive weapons but of limited use for hunting.

Animal food appears to have been part of the later hominid diet and would have been much more likely if fire was in use for cooking, but consumption of meat does not necessarily provide evidence of hunting large animals. If a shower of stones could drive a leopard away from an infant, it could also drive it away from an animal which it had just killed. Perhaps it was possible to obtain big game by waiting at a water hole until a heavy animal was killed by a predator and then driving the predator off the carcase with missiles. Perhaps our hominid predecessors were prey-stealers rather than predators. In this they would not have been unusual: all predators are on the lookout for recent kills by their predator competitors, and a recent victim is not always even initially eaten - and hardly ever completely eaten - by the predator which killed him.

The gradual development of hominds continued until around 100,000 years ago - later in some parts of the world. Brain size almost doubled; geographical range expanded into cold areas of Europe; stone artifacts were gradually perfected. But there was an astonishing continuity. In particular the dominance of hand axes for almost the whole period of pre-sapiens hominid development - more than a million years, during which time brain size almost doubled - is extraordinary. Later hand axes are much better made, but they are essentially the same tools as those originally invented and presumably were used in the same way. There were other stone implements; but there is no evidence of bone, antlers or ivory being used as materials for deliberate tool-making on standard patterns until around 60,000 years ago

The Hominid Environment

60,000 years ago - only three or four thousand human generations - our picture of the past shows us a world which was still dominated by very large animals. In particular, mammoths and other members of the elephant family existed in huge numbers almost everywhere in the world. Elephants feared few predators and had adapted to almost every kind of climate. Their overwhelming influence on the environment - still true of a few small areas of Africa - was probably once the rule almost everywhere.

The elephant has shaped much of the natural African landscape, rendering it more fit for habitation by human beings... As they forage, elephants create and maintain broad paths through impenetrable bamboo and elephant grass belts, and in forested areas, they keep extensive glades in permanent state of early succession, not only breaking down trees but also tearing up acres of saplings for their roots. They excavate and weed out water holes, and “garden” interconnected glades and clearings into tangled vegetation.

(Chapurukha Kusimba)

Elephants make tracks through forest which man and other animals subsequently use; many of our present-day roads may well have originated in this way. They dig wells which are subsequently used by other animals:

The wells that they dig can reach nearly 2m in depth. Most well-digging is initiated by adult males, which locate the best places to dig by finding damp places on the ground surface. ..Wells dug by elephants collapse after the rains begin, yet they are invariably redug within a few feet of where they had been located before..

(Gary Haynes (1991) Mammoths, Mastodonts & Elephants)

Until the appearance of modern humans, the elephant was undoubtedly nature's masterpiece. Elephants are highly intelligent animals and until the appearance of the bipeds, the only mammals which could manipulate objects without needing to to use limbs intended mainly for walking, running or climbing. The elephant trunk is immensely strong yet (it has been reported) able to pick individual blades of grass. Elephants appear to have sophisticated means of communication over distances using low-frequency notes which we cannot hear.

The elephants of the past - which we call mammoths - were closely related to modern elephants (though some of them were considerably bigger) and are likely to have behaved very similarly:

Great differences in the social behaviours of the extinct species seem unlikely; the two surviving taxa (African and Indian elephants) diverged from a common ancestry millions of years ago and yet today they display behaviors that are strikingly similar. Their behaviors might therefore be similar to to those of directly ancestral or closely related extinct forms.

(Haynes)

It is easy and probably correct to imagine woolly mammoths providing drinking water for themselves (and of course others) by breaking holes in the ice on frozen Siberian rivers and lakes.

Besides mammoths, the hominid environment included many other huge and powerful animals, now extinct. They had tough hides. How effective would stone missiles, clubs and wooden spears have been against a herd of mammoths, some of them twice the size of an African elephant? The hominids who lived before the coming of modern man (up to only at most 5000 generations ago in Europe) probably always lived in fear of large animals and had little control over the environment in which they lived. Agriculture was inconceivable because crops would have been trampled and eaten. Permanent dwellings (unless in caves or other inaccessible locations) would always have been liable to be overrun.

To sum up: during a very long period of development, the australopithecines and hominids survived and created a favourable ecological niche for themselves, probably above all because they could defend themselves and their young by the use of natural and artificial weapons - particularly missiles - which enabled them to keep their enemies at a safe distance. The same skills also probably enabled them to kill small animals and to actively scavenge the flesh of larger animals by driving predators away from their kills. Like chimpanzees, they could make tools and weapons out of perishable materials; unlike chimpanzees, they also learned to shape stones and this greatly extended their armoury and toolkit. They were highly intelligent and they were possibly the only primates to successfully colonise colder climates. Probably they had the use of fire. But their environment was dominated by animals much larger and more powerful than themselves; they lived in the shadow of the megafauna.

What kind of creatures were they? Were they people like ourselves? Can we imagine humans so conservative that their technology remained almost unchanged for a million years? Yet in contrast to the australopithecines, the later varieties now classified as Homo had skeletons and even (in later animals) brain capacity little different from our own. Nevertheless we must avoid anthropomorphism: skeletal resemblance is not enough. In particular, we should not assume necessarily that our hominid predecessors had our typically human powers of speech. There are some good reasons for suggesting that they had not.

Language and Social Organization

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