A short history of nearly everything

hominid and early human bones.

The shortage wouldn’t be so bad if the bones were distributed evenly through time and space, but of course they are not. They appear randomly, often in the most tantalizing fashion. Homo erectus walked the Earth for well over a million years and inhabited territory from the Atlantic edge of Europe to the Pacific side of China, yet if you brought back to life every Homo erectus individual whose existence we can vouch for, they wouldn’t fill a school bus. Homo habilis consists of even less: just two partial skeletons and a number of isolated limb bones. Something as short-lived as our own civilization would almost certainly not be known from the fossil record at all.

“In Europe,” Tattersall offers by way of illustration, “you’ve got hominid skulls in Georgia dated to about 1.7 million years ago, but then you have a gap of almost a million years before the next remains turn up in Spain, right on the other side of the continent, and then you’ve got another 300,000-year gap before you get a Homo heidelbergensis in Germany-and none of them looks terribly much like any of the others.” He smiled. “It’s from these kinds of fragmentary pieces that you’re trying to work out the histories of entire species. It’s quite a tall order. We really have very little idea of the relationships between many ancient species- which led to us and which were evolutionary dead ends. Some probably don’t deserve to be regarded as separate species at all.”

It is the patchiness of the record that makes each new find look so sudden and distinct from all the others. If we had tens of thousands of skeletons distributed at regular intervals through the historical record, there would be appreciably more degrees of shading. Whole new species don’t emerge instantaneously, as the fossil record implies, but gradually out of other, existing species. The closer you go back to a point of divergence, the closer the similarities are, so that it becomes exceedingly difficult, and sometimes impossible, to distinguish a late Homo erectus from an early Homo sapiens, since it is likely to be both and neither. Similar disagreements can often arise over questions of identification from fragmentary remains-deciding, for instance, whether a particular bone represents a female Australopithecus boisei or a male Homo habilis.

With so little to be certain about, scientists often have to make assumptions based on other objects found nearby, and these may be little more than valiant guesses. As Alan Walker and Pat Shipman have drily observed, if you correlate tool discovery with the species of creature most often found nearby, you would have to conclude that early hand tools were mostly made by antelopes.

Perhaps nothing better typifies the confusion than the fragmentary bundle of contradictions that was Homo habilis. Simply put, habilis bones make no sense. When arranged in sequence, they show males and females evolving at different rates and in different directions-the males becoming less apelike and more human with time, while females from the same period appear to be moving away from humanness toward greater apeness. Some authorities don’t believe habilis is a valid category at all. Tattersall and his colleague Jeffrey Schwartz dismiss it as a mere “wastebasket species”-one into which unrelated fossils “could be conveniently swept.” Even those who see habilis as an independent species don’t agree on whether it is of the same genus as us or is from a side branch that never came to anything.

Finally, but perhaps above all, human nature is a factor in all this. Scientists have a natural tendency to interpret finds in the way that most flatters their stature. It is a rare paleontologist indeed who announces that he has found a cache of bones but that they are nothing to get excited about. Or as John Reader understatedly observes in the book Missing Links, “It is remarkable how often the first interpretations of new evidence have confirmed the preconceptions of its discoverer.”

All this leaves ample room for arguments, of course, and nobody likes to argue more than paleoanthropologists. “And of all the disciplines in science, paleoanthropology boasts perhaps the largest share of egos,” say the authors of the recent Java Man-a book, it may be noted, that itself devotes long, wonderfully unselfconscious passages to attacks on the inadequacies of others, in particular the authors’ former close colleague Donald Johanson. Here is a small sampling:

In our years of collaboration at the institute he [Johanson] developed a well-deserved, if unfortunate, reputation for unpredictable and high-decibel personal verbal assaults, sometimes accompanied by the tossing around of books or whatever else came conveniently to hand.

So, bearing in mind that there is little you can say about human prehistory that won’t be disputed by someone somewhere, other than that we most certainly had one, what we think we know about who we are and where we come from is roughly this:

For the first 99.99999 percent of our history as organisms, we were in the same ancestral line as chimpanzees. Virtually nothing is known about the prehistory of chimpanzees, but whatever they were, we were. Then about seven million years ago something major happened. A group of new beings emerged from the tropical forests of Africa and began to move about on the open savanna.

These were the australopithecines, and for the next five million years they would be the world’s dominant hominid species. (Austral is from the Latin for “southern” and has no connection in this context to Australia.) Australopithecines came in several varieties, some slender and gracile, like Raymond Dart’s Taung child, others more sturdy and robust, but all were capable of walking upright. Some of these species existed for well over a million years, others for a more modest few hundred thousand, but it is worth bearing in mind that even the least successful had histories many times longer than we have yet achieved.

The most famous hominid remains in the world are those of a 3.18-million-year-old australopithecine found at Hadar in Ethiopia in 1974 by a team led by Donald Johanson. Formally known as A.L. (for “Afar Locality”) 288-1, the skeleton became more familiarly known as Lucy, after the Beatles song “Lucy in the Sky with Diamonds.” Johanson has never doubted her importance. “She is our earliest ancestor, the missing link between ape and human,” he has said.

Lucy was tiny-just three and a half feet tall. She could walk, though how well is a matter of some dispute. She was evidently a good climber, too. Much else is unknown. Her skull was almost entirely missing, so little could be said with confidence about her brain size, though skull fragments suggested it was small. Most books describe Lucy’s skeleton as being 40 percent complete, though some put it closer to half, and one produced by the American Museum of Natural History describes Lucy as two-thirds complete. The BBC television series Ape Man actually called it “a complete skeleton,” even while showing that it was anything but.

A human body has 206 bones, but many of these are repeated. If you have the left femur from a specimen, you don’t need the right to know its dimensions. Strip out all the redundant bones, and the total you are left with is 120-what is called a half skeleton. Even by this fairly accommodating standard, and even counting the slightest fragment as a full bone, Lucy constituted only 28 percent of a half skeleton (and only about 20 percent of a full one).

In The Wisdom of the Bones, Alan Walker recounts how he once asked Johanson how he had come up with a figure of 40 percent. Johanson breezily replied that he had discounted the 106 bones of the hands and feet-more than half the body’s total, and a fairly important half, too, one would have thought, since Lucy’s principal defining attribute was the use of those hands and feet to deal with a changing world. At all events, rather less is known about Lucy than is generally supposed. It isn’t even actually known that she was a female. Her sex is merely presumed from her diminutive size.

Two years after Lucy’s discovery, at Laetoli in Tanzania Mary Leakey found footprints left by two individuals from-it is thought-the same family of hominids. The prints had been made when two australopithecines had walked through muddy ash following a volcanic eruption. The ash had later hardened, preserving the impressions of their feet for a distance of over twenty-three meters.

The American Museum of Natural History in New York has an absorbing diorama that records the moment of their passing. It depicts life-sized re-creations of a male and a female walking side by side across the ancient African plain. They are hairy and chimplike in dimensions, but have a bearing and gait that suggest humanness. The most striking feature of the display is that the male holds his left arm protectively around the female’s shoulder. It is a tender and affecting gesture, suggestive of close bonding.

The tableau is done with such conviction that it is easy to overlook the consideration that virtually