A short history of nearly everything (62 page)

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 textbookThe 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 disputedHomo habilis . This isHomo 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 theJava 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.

Erectuswas “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 appear 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.

Althougherectus 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 completeHomo 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 thatHomo 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 thatHomo 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 thatHomo 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 howHomo 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 oldererectus 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 areHomo erectus at all. The snag, ironically, was that although the Turkana skeletons were admirably extensive, all othererectusfossils are inconclusively fragmentary. As Tattersall and Jeffrey Schwartz note inExtinct 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 AsianHomo 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 wasergaster“or a reasonably close relative” that spread to Asia from Africa, evolved intoHomo 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.

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 earlyHomo sapiens loved 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 thatHomo 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 ofHomo erectus , which became Java Man and Peking Man and the like, and a later, more advanced wave ofHomo sapiens , which displaced the first lot. Yet to accept that you must believe thatHomo sapiensgot 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?

The answer, provided by carbon dating, was that the bones’ owner had lived there when Lake Mungo was a much more agreeable habitat, a dozen miles long, full of water and fish, fringed by pleasant groves of casuarina trees. To everyone’s astonishment, the bones turned out to be 23,000 years old. Other bones found nearby were dated to as much as 60,000 years. This was unexpected to the point of seeming practically impossible. At no time since hominids first arose on Earth has Australia not been an island. Any human beings who arrived there must have come by sea, in large enough numbers to start a breeding population, after crossing sixty miles or more of open water without having any way of knowing that a convenient landfall awaited them. Having landed, the Mungo people had then found their way more than two thousand miles inland from Australia’s north coast—the presumed point of entry—which suggests, according to a report in the Proceedings of the National Academy of Sciences, “that people may have first arrived substantially earlier than 60,000 years ago.”

How they got there and why they came are questions that can’t be answered. According to most anthropology texts, there’s no evidence that people could even speak 60,000 years ago, much less engage in the sorts of cooperative efforts necessary to build ocean-worthy craft and colonize island continents.