No single, essential difference separates human beings from other animals -- but that hasn't stopped the phrasemakers from trying to find one. They have described humans as the animals who make tools, or reason, or use fire, or laugh, or any one of a dozen other appealing oversimplifications. Here's one more description for the list, as good as any other: Humans are the animals who wonder, intensely and endlessly, about their origin. Starting with a Neanderthal skeleton unearthed in Germany in 1856, archaeologists and anthropologists have sweated mightily over excavations in Africa, Europe and Asia, trying to find fossil evidence that will answer the most fundamental questions of our existence: When, where and how did the human race arise? Nonscientists are as eager for the answers as the experts, if the constant outpouring of books and documentaries on the subject is any indication. The latest, a three-part Nova show titled In Search of Human Origins, premiered last week.
Yet despite more than a century of digging, the fossil record remains maddeningly sparse. With so few clues, even a single bone that doesn't fit into the picture can upset everything. Virtually every major discovery has put deep cracks in the conventional wisdom and forced scientists to concoct new theories, amid furious debate.
Now it appears to be happening once again. Findings announced in the past two weeks are rattling the foundations of anthropology and raising some startling possibilities. Humanity's ancestors may have departed Africa -- the cradle of mankind -- eons earlier than scientists have assumed. Humans may have evolved not just in a single place but in many places around the world. And our own species, Homo sapiens, may be much older than anyone had suspected. If even portions of these claims prove to be true, they will force a major rewrite of the book of human evolution. They will herald fundamental changes in the story of how we came to be who we are.
The latest shocker comes in the current issue of Nature, where Chinese scientists have contended that the skull of a modern-looking human, found in their country a decade ago, is at least 200,000 years old -- more than twice as old as any Homo sapiens specimen ever found in that part of the world. Moreover, the skull has features resembling those of contemporary Asians. The controversial implication: modern humans may not have evolved just in Africa, as most scientists believe, but may have emerged simultaneously in several regions of the globe.
The Nature article came only a week after an even more surprising report in the competing journal Science. U.S. and Indonesian researchers said they had redated fossil skull fragments found at two sites on the island of Java. Instead of being a million years old, as earlier analysis suggested, the fossils appear to date back nearly 2 million years. They are from the species known as Homo erectus -- the first primate to look anything like modern humans and the first to use fire and create sophisticated stone tools. Says F. Clark Howell, an anthropologist at the University of California, Berkeley: "This is just overwhelming. No one expected such an age."