RETURN TO THE HOMINID JOURNEY....
The roots of this mystery run deep, all the way back to 1856, when the science of paleoanthropology had not yet been born. That year, workers mining a limestone cave in Germany's Neander Valley came across a truly peculiar skeleton. This was the first Neanderthal ever found, and he was to become the leading man in the bones and stones part of the story.
To Johann Fuhlrott, the natural science teacher who first described the remains, the Neanderthal seemed to defy categorization. The limbs of the skeleton, though unusually thick, looked human enough and supported a very stocky and muscular frame. His braincase was actually larger than a modern human's. But his facial features were unlike any then known. In the book Origins Reconsidered anthropologist Richard Leakey and writer Roger Lewin offer this visual aid: "Imagine a modern human face made of rubber. Now take hold of the nose and pull it out several inches. The result is an oddly protruding central portion of the face, not just the nose but everything around it. That, roughly speaking, is a Neanderthal face."
The Neanderthals, always a puzzle to science, are now central to the debate over modern human origins. Descendants of Homo erectus, the Neanderthals lived from about 150,000 to 30,000 years ago in a broad swath of Eurasia stretching from the Iberian Peninsula to Uzbekistan. Although the Neanderthals weren't the only descendants of Homo erectus, their bones and tools are far more abundant than those of any other early humans. This is one reason they loom large in the controversy: They give paleoanthropologists plenty to argue about.
The burning question is whether the Neanderthals gave rise to us. And for years, the answer seemed pretty clear. Most scientists once interpreted the Neanderthals as an evolutionary transition between Homo erectus and ourselves. This view seemed to square with the broad patterns of the fossil record. For example, early this century scientists found 60,000-year-old Neanderthal remains in three caves in Israel. In two nearby caves they found modern-looking skeletons presumed to be 40,000 to 50,000 years old. Since the Neanderthals were respectably older than the moderns, there was no reason to doubt that the Neanderthals were our ancestors. In fact, the Neanderthal and modern human remains from two of the caves were thought to represent a single population that evolved gradually over time.
But by 1988, this tidy picture was shattered. Re-dating the fossils with new techniques, researchers learned that the modern humans from two of the caves were actually 80,000 to 100,000 years old, older than most of the Neanderthals. Now here was a thorny problem. If modern humans were around before and during the Neanderthals' existence, how could they be descendants of the Neanderthals? The evidence suggested that Neanderthals did not fit in a direct line from Homo erectus to us. Instead, Neanderthals and modern humans occupied separate branches on the evolutionary tree.
"The fact that in the Middle East you have moderns and Neanderthals remaining distinct over tens of thousands of years proves that they were two well-separated lineages," says Christopher Stringer, a paleoanthropologist at London's Natural History Museum. Moreover, though Neanderthals and modern humans coexisted for a time, Stringer believes that Earth ultimately wasn't big enough for the both of them. By 30,000 years ago, undisputed Neanderthal fossils disappear from the record in Europe, the last Neanderthal stronghold, and modern human fossils become abundant. Thus Stringer and many others believe that our ancestors wiped the Neanderthals off the face of the globe.
So who were these people who allegedly annihilated the Neanderthals? The fossil evidence may give a clue. In caves at the mouth of the Klasies River in South Africa, and in thick sediments of Ethiopia's Omo Basin, researchers have uncovered remains of modern-looking humans, dating back some 80,000 to 120,000 years. These are, arguably, the very oldest bones of Homo sapiens ever found. To Stringer and many other scientists, they offer compelling evidence that Africa is the birthplace of modern humans as well as the birthplace of the very first humans millions of years ago. The first modern humans, Stringer and colleagues say, were Africans. They -- we -- migrated to the Middle East and from there spread across Earth.
No one knows what presumably triggered the emergence of modern-looking humans in Africa or their migration into the rest of the world. Nor do scientists know why or how the Neanderthals and other human groups vanished. Multiregionalists resolve the problem by concluding that Neanderthals never truly disappeared; they simply interbred with modern humans until the two groups melded ("a great Pleistocene love-in," as Tattersall facetiously describes it). A vigorous supporter of the replacement idea, Tattersall himself thinks Neanderthals were more likely slaughtered by moderns: "You can't think of very many examples of Homo sapiens showing up on the territory of another group and everybody living happily ever after. It just doesn't seem to happen."
On the other hand, as Stringer points out, it's also possible that modern humans quietly edged out the competition. Though our ancestors were physically weaker than the Neanderthals, they might have been better able to communicate or plan ahead for the torturous winters. Even subtle cultural differences could have eventually tipped the scales so that our populations grew and the Neanderthals' shrank until they became extinct. "Perhaps if we hadn't come into Europe 40,000 years ago, the Neanderthals would still be here now," Stringer says. "Who knows? Maybe I would be speaking to you on the phone as a Neanderthal."