A Short History of Nearly Everything

by Bill Bryson

  Matters grew murkier still in 2001 and 2002 when four exceptional new specimens were found. One, discovered by Meave Leakey of the famous fossil-hunting family at Lake Turkana in Kenya and called Kenyanthropus platyops ("Kenyan flat-face"), is from about the same time as Lucy and raises the possibility that it was our ancestor and Lucy was an unsuccessful side branch. Also found in 2001 were Ardipithecus ramidus kadabba , dated at between 5.2 million and 5.8 million years old, and Orrorin tugenensis , thought to be 6 million years old, making it the oldest hominid yet found--but only for a brief while. In the summer of 2002 a French team working in the Djurab Desert of Chad (an area that had never before yielded ancient bones) found a hominid almost 7 million years old, which they labeled Sahelanthropus tchadensis . (Some critics believe that it was not human, but an early ape and therefore should be called Sahelpithecus .) All these were early creatures and quite primitive but they walked upright, and they were doing so far earlier than previously thought.

  Bipedalism is a demanding and risky strategy. It means refashioning the pelvis into a full load-bearing instrument. To preserve the required strength, the birth canal must be comparatively narrow. This has two very significant immediate consequences and one longer-term one. First, it means a lot of pain for any birthing mother and a greatly increased danger of fatality to mother and baby both. Moreover to get the baby's head through such a tight space it must be born while its brain is still small--and while the baby, therefore, is still helpless. This means long-term infant care, which in turn implies solid male-female bonding.

  All this is problematic enough when you are the intellectual master of the planet, but when you are a small, vulnerable australopithecine, with a brain about the size of an orange, * 48 the risk must have been enormous.

  So why did Lucy and her kind come down from the trees and out of the forests? Probably they had no choice. The slow rise of the Isthmus of Panama had cut the flow of waters from the Pacific into the Atlantic, diverting warming currents away from the Arctic and leading to the onset of an exceedingly sharp ice age in northern latitudes. In Africa, this would have produced seasonal drying and cooling, gradually turning jungle into savanna. "It was not so much that Lucy and her like left the forests," John Gribbin has written, "but that the forests left them."

  But stepping out onto the open savanna also clearly left the early hominids much more exposed. An upright hominid could see better, but could also be seen better. Even now as a species, we are almost preposterously vulnerable in the wild. Nearly every large animal you can care to name is stronger, faster, and toothier than us. Faced with attack, modern humans have only two advantages. We have a good brain, with which we can devise strategies, and we have hands with which we can fling or brandish hurtful objects. We are the only creature that can harm at a distance. We can thus afford to be physically vulnerable.

  All the elements would appear to have been in place for the rapid evolution of a potent brain, and yet that seems not to have happened. For over three million years, Lucy and her fellow australopithecines scarcely changed at all. Their brain didn't grow and there is no sign that they used even the simplest tools. What is stranger still is that we now know that for about a million years they lived alongside other early hominids who did use tools, yet the australopithecines never took advantage of this useful technology that was all around them.

  At one point between three and two million years ago, it appears there may have been as many as six hominid types coexisting in Africa. Only one, however, was fated to last: Homo , which emerged from the mists beginning about two million years ago. No one knows quite what the relationship was between australopithecines and Homo, but what is known is that they coexisted for something over a million years before all the australopithecines, robust and gracile alike, vanished mysteriously, and possibly abruptly, over a million years ago. No one knows why they disappeared. "Perhaps," suggests Matt Ridley, "we ate them."

  Conventionally, the Homo line begins with Homo habilis , a creature about whom we know almost nothing, and concludes with us, Homo sapiens (literally "man the thinker"). In between, and depending on which opinions you value, there have been half a dozen other Homo species: Homo ergaster, Homo neanderthalensis, Homo rudolfensis, Homo heidelbergensis, Homo erectus , and Homo antecessor .

  Homo habilis ("handy man") was named by Louis Leakey and colleagues in 1964 and was so called because it was the first hominid to use tools, albeit very simple ones. It was a fairly primitive creature, much more chimpanzee than human, but its brain was about 50 percent larger than that of Lucy in gross terms and not much less large proportionally, so it was the Einstein of its day. No persuasive reason has ever been adduced for why hominid brains suddenly began to grow two million years ago. For a long time it was assumed that big brains and upright walking were directly related--that the movement out of the forests necessitated cunning new strategies that fed off of or promoted braininess--so it was something of a surprise, after the repeated discoveries of so many bipedal dullards, to realize that there was no apparent connection between them at all.

  "There is simply no compelling reason we know of to explain why human brains got large," says Tattersall. Huge brains are demanding organs: they make up only 2 percent of the body's mass, but devour 20 percent of its energy. They are also comparatively picky in what they use as fuel. If you never ate another morsel of fat, your brain would not complain because it won't touch the stuff. It wants glucose instead, and lots of it, even if it means short-changing other organs. As Guy Brown notes: "The body is in constant danger of being depleted by a greedy brain, but cannot afford to let the brain go hungry as that would rapidly lead to death." A big brain needs more food and more food means increased risk.

  Tattersall thinks the rise of a big brain may simply have been an evolutionary accident. He believes with Stephen Jay Gould that if you replayed the tape of life--even if you ran it back only a relatively short way to the dawn of hominids--the chances are "quite unlikely" that modern humans or anything like them would be here now.

  "One of the hardest ideas for humans to accept," he says, "is that we are not the culmination of anything. There is nothing inevitable about our being here. It is part of our vanity as humans that we tend to think of evolution as a process that, in effect, was programmed to produce us. Even anthropologists tended to think this way right up until the 1970s." Indeed, as recently as 1991, in the popular textbook The Stages of Evolution , C. Loring Brace stuck doggedly to the linear concept, acknowledging just one evolutionary dead end, the robust australopithecines. Everything else represented a straightforward progression--each species of hominid carrying the baton of development so far, then handing it on to a younger, fresher runner. Now, however, it seems certain that many of these early forms followed side trails that didn't come to anything.

  Luckily for us, one did--a group of tool users, which seemed to arise from out of nowhere and overlapped with the shadowy and much disputed Homo habilis . This is Homo erectus , the species discovered by Eugène Dubois in Java in 1891. Depending on which sources you consult, it existed from about 1.8 million years ago to possibly as recently as twenty thousand or so years ago.

  According to the Java Man authors, Homo erectus is the dividing line: everything that came before him was apelike in character; everything that came after was humanlike. Homo erectus was the first to hunt, the first to use fire, the first to fashion complex tools, the first to leave evidence of campsites, the first to look after the weak and frail. Compared with all that had gone before, Homo erectus was extremely human in form as well as behavior, its members long-limbed and lean, very strong (much stronger than modern humans), and with the drive and intelligence to spread successfully over huge areas. To other hominids, Homo erectus must have seemed terrifyingly powerful, fleet, and gifted.

  Erectus was "the velociraptor of its day," according to Alan Walker of Penn State University and one of the world's leading authorities. If you were to look one in the eyes, it might appea
r superficially to be human, but "you wouldn't connect. You'd be prey." According to Walker, it had the body of an adult human but the brain of a baby.

  Although erectus had been known about for almost a century it was known only from scattered fragments--not enough to come even close to making one full skeleton. So it wasn't until an extraordinary discovery in Africa in the 1980s that its importance--or, at the very least, possible importance--as a precursor species for modern humans was fully appreciated. The remote valley of Lake Turkana (formerly Lake Rudolf) in Kenya is now one of the world's most productive sites for early human remains, but for a very long time no one had thought to look there. It was only because Richard Leakey was on a flight that was diverted over the valley that he realized it might be more promising than had been thought. A team was dispatched to investigate, but at first found nothing. Then late one afternoon Kamoya Kimeu, Leakey's most renowned fossil hunter, found a small piece of hominid brow on a hill well away from the lake. Such a site was unlikely to yield much, but they dug anyway out of respect for Kimeu's instincts and to their astonishment found a nearly complete Homo erectus skeleton. It was from a boy aged between about nine and twelve who had died 1.54 million years ago. The skeleton had "an entirely modern body structure," says Tattersall, in a way that was without precedent. The Turkana boy was "very emphatically one of us."

  Also found at Lake Turkana by Kimeu was KNM-ER 1808, a female 1.7 million years old, which gave scientists their first clue that Homo erectus was more interesting and complex than previously thought. The woman's bones were deformed and covered in coarse growths, the result of an agonizing condition called hypervitaminosis A, which can come only from eating the liver of a carnivore. This told us first of all that Homo erectus was eating meat. Even more surprising was that the amount of growth showed that she had lived weeks or even months with the disease. Someone had looked after her. It was the first sign of tenderness in hominid evolution.

  It was also discovered that Homo erectus skulls contained (or, in the view of some, possibly contained) a Broca's area, a region of the frontal lobe of the brain associated with speech. Chimps don't have such a feature. Alan Walker thinks the spinal canal didn't have the size and complexity to enable speech, that they probably would have communicated about as well as modern chimps. Others, notably Richard Leakey, are convinced they could speak.

  For a time, it appears, Homo erectus was the only hominid species on Earth. It was hugely adventurous and spread across the globe with what seems to have been breathtaking rapidity. The fossil evidence, if taken literally, suggests that some members of the species reached Java at about the same time as, or even slightly before, they left Africa. This has led some hopeful scientists to suggest that perhaps modern people arose not in Africa at all, but in Asia--which would be remarkable, not to say miraculous, as no possible precursor species have ever been found anywhere outside Africa. The Asian hominids would have had to appear, as it were, spontaneously. And anyway an Asian beginning would merely reverse the problem of their spread; you would still have to explain how the Java people then got to Africa so quickly.

  There are several more plausible alternative explanations for how Homo erectus managed to turn up in Asia so soon after its first appearance in Africa. First, a lot of plus-or-minusing goes into the dating of early human remains. If the actual age of the African bones is at the higher end of the range of estimates or the Javan ones at the lower end, or both, then there is plenty of time for African erects to find their way to Asia. It is also entirely possible that older erectus bones await discovery in Africa. In addition, the Javan dates could be wrong altogether.

  Now for the doubts. Some authorities don't believe that the Turkana finds are Homo erectus at all. The snag, ironically, was that although the Turkana skeletons were admirably extensive, all other erectus fossils are inconclusively fragmentary. As Tattersall and Jeffrey Schwartz note in Extinct Humans , most of the Turkana skeleton "couldn't be compared with anything else closely related to it because the comparable parts weren't known!" The Turkana skeletons, they say, look nothing like any Asian Homo erectus and would never have been considered the same species except that they were contemporaries. Some authorities insist on calling the Turkana specimens (and any others from the same period) Homo ergaster . Tattersall and Schwartz don't believe that goes nearly far enough. They believe it was ergaster "or a reasonably close relative" that spread to Asia from Africa, evolved into Homo erectus, and then died out.

  What is certain is that sometime well over a million years ago, some new, comparatively modern, upright beings left Africa and boldly spread out across much of the globe. They possibly did so quite rapidly, increasing their range by as much as twenty-five miles a year on average, all while dealing with mountain ranges, rivers, deserts, and other impediments and adapting to differences in climate and food sources. A particular mystery is how they passed along the west side of the Red Sea, an area of famously punishing aridity now, but even drier in the past. It is a curious irony that the conditions that prompted them to leave Africa would have made it much more difficult to do so. Yet somehow they managed to find their way around every barrier and to thrive in the lands beyond.

  And that, I'm afraid, is where all agreement ends. What happened next in the history of human development is a matter of long and rancorous debate, as we shall see in the next chapter.

  But it is worth remembering, before we move on, that all of these evolutionary jostlings over five million years, from distant, puzzled australopithecine to fully modern human, produced a creature that is still 98.4 percent genetically indistinguishable from the modern chimpanzee. There is more difference between a zebra and a horse, or between a dolphin and a porpoise, than there is between you and the furry creatures your distant ancestors left behind when they set out to take over the world.

  29 THE RESTLESS APE

  SOMETIME ABOUT A million and a half years ago, some forgotten genius of the hominid world did an unexpected thing. He (or very possibly she) took one stone and carefully used it to shape another. The result was a simple teardrop-shaped hand axe, but it was the world's first piece of advanced technology.

  It was so superior to existing tools that soon others were following the inventor's lead and making hand axes of their own. Eventually whole societies existed that seemed to do little else. "They made them in the thousands," says Ian Tattersall. "There are some places in Africa where you literally can't move without stepping on them. It's strange because they are quite intensive objects to make. It was as if they made them for the sheer pleasure of it."

  From a shelf in his sunny workroom Tattersall took down an enormous cast, perhaps a foot and a half long and eight inches wide at its widest point, and handed it to me. It was shaped like a spearhead, but one the size of a stepping-stone. As a fiberglass cast it weighed only a few ounces, but the original, which was found in Tanzania, weighed twenty-five pounds. "It was completely useless as a tool," Tattersall said. "It would have taken two people to lift it adequately, and even then it would have been exhausting to try to pound anything with it."

  "What was it used for then?"

  Tattersall gave a genial shrug, pleased at the mystery of it. "No idea. It must have had some symbolic importance, but we can only guess what."

  The axes became known as Acheulean tools, after St. Acheul, a suburb of Amiens in northern France, where the first examples were found in the nineteenth century, and contrast with the older, simpler tools known as Oldowan, originally found at Olduvai Gorge in Tanzania. In older textbooks, Oldowan tools are usually shown as blunt, rounded, hand-sized stones. In fact, paleoanthropologists now tend to believe that the tool part of Oldowan rocks were the pieces flaked off these larger stones, which could then be used for cutting.

  Now here's the mystery. When early modern humans--the ones who would eventually become us--started to move out of Africa something over a hundred thousand years ago, Acheulean tools were the technology of choice. These early Homo sapiens l
oved their Acheulean tools, too. They carried them vast distances. Sometimes they even took unshaped rocks with them to make into tools later on. They were, in a word, devoted to the technology. But although Acheulean tools have been found throughout Africa, Europe, and western and central Asia, they have almost never been found in the Far East. This is deeply puzzling.

  In the 1940s a Harvard paleontologist named Hallum Movius drew something called the Movius line, dividing the side with Acheulean tools from the one without. The line runs in a southeasterly direction across Europe and the Middle East to the vicinity of modern-day Calcutta and Bangladesh. Beyond the Movius line, across the whole of southeast Asia and into China, only the older, simpler Oldowan tools have been found. We know that Homo sapiens went far beyond this point, so why would they carry an advanced and treasured stone technology to the edge of the Far East and then just abandon it?

  "That troubled me for a long time," recalls Alan Thorne of the Australian National University in Canberra. "The whole of modern anthropology was built round the idea that humans came out of Africa in two waves--a first wave of Homo erectus , which became Java Man and Peking Man and the like, and a later, more advanced wave of Homo sapiens , which displaced the first lot. Yet to accept that you must believe that Homo sapiens got so far with their more modern technology and then, for whatever reason, gave it up. It was all very puzzling, to say the least."

  As it turned out, there would be a great deal else to be puzzled about, and one of the most puzzling findings of all would come from Thorne's own part of the world, in the outback of Australia. In 1968, a geologist named Jim Bowler was poking around on a long-dried lakebed called Mungo in a parched and lonely corner of western New South Wales when something very unexpected caught his eye. Sticking out of a crescent-shaped sand ridge of a type known as a lunette were some human bones. At the time, it was believed that humans had been in Australia for no more than 8,000 years, but Mungo had been dry for 12,000 years. So what was anyone doing in such an inhospitable place?