Bill Bryson - A short history of nearly everything

In the following years as more bones were found and identified there came a flood of new names- Homo aurignacensis, Australopithecus transvaalensis, Paranthropus crassidens, Zinjanthropus boisei, and scores of others, nearly all involving a new genus type as well as a new species. By the 1950s, the number of named hominid types had risen to comfortably over a hundred. To add to the confusion, individual forms often went by a succession of different names as paleoanthropologists refined, reworked, and squabbled over classifications. Solo People were known variously as Homo soloensis, Homo primigenius asiaticus, Homo neanderthalensis soloensis, Homo sapiens soloensis, Homo erectus erectus, and, finally, plain Homo erectus .

In an attempt to introduce some order, in 1960 F. Clark Howell of the University of Chicago, following the suggestions of Ernst Mayr and others the previous decade, proposed cutting the number of genera to just two- Australopithecus and Homo -and rationalizing many of the species. The Java and Peking men both became Homo erectus . For a time order prevailed in the world of the hominids. [47]It didn’t last.

After about a decade of comparative calm, paleoanthropology embarked on another period of swift and prolific discovery, which hasn’t abated yet. The 1960s produced Homo habilis , thought by some to be the missing link between apes and humans, but thought by others not to be a separate species at all. Then came (among many others) Homo ergaster, Homo louisleakeyi, Homo rudolfensis, Homo microcranus, and Homo antecessor , as well as a raft of australopithecines: A. afarensis, A. praegens, A. ramidus, A. walkeri, A. anamensis , and still others. Altogether, some twenty types of hominid are recognized in the literature today. Unfortunately, almost no two experts recognize the same twenty.

Some continue to observe the two hominid genera suggested by Howell in 1960, but others place some of the australopithecines in a separate genus called Paranthropus , and still others add an earlier group called Ardipithecus . Some put praegens into Australopithecus and some into a new classification, Homo antiquus , but most don’t recognize praegens as a separate species at all. There is no central authority that rules on these things. The only way a name becomes accepted is by consensus, and there is often very little of that.

A big part of the problem, paradoxically, is a shortage of evidence. Since the dawn of time, several billion human (or humanlike) beings have lived, each contributing a little genetic variability to the total human stock. Out of this vast number, the whole of our understanding of human prehistory is based on the remains, often exceedingly fragmentary, of perhaps five thousand individuals. “You could fit it all into the back of a pickup truck if you didn’t mind how much you jumbled everything up,” Ian Tattersall, the bearded and friendly curator of anthropology at the American Museum of Natural History in New York, replied when I asked him the size of the total world archive of 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.