An Ancient Wanderlust
Earlier that january day in 1990, the Chinese scientists had asked Russell Ciochon if they could meet with him out of earshot of colleagues at Beijing's Institute of Vertebrate Paleontology and Paleoanthropology. Ciochon, a University of Iowa expert in early humans--hominids--was in China for a project on an extinct ape. His curiosity piqued, he invited Huang Wanpo and his wife, Gu Yumin, to his hotel. After the usual pleasantries over jasmine tea, Huang reached into his pocket and pulled out the cast of a tiny jaw from an ancient--very ancient-human ancestor. It was from the Longgupo Caves, he said, in Sichuan province. Huang needed a Western collaborator to determine the age of the fossil and present it to the world, he said. Did Ciochon, in Beijing when most Westerners were shunning China in the wake of the Tiananmen Square massacre, care to help?
Did he ever. And now it's paid off. Last week, Huang, Ciochon, Gu and six other scientists reported in the journal Nature that the little jaw in Huang's pocket, plus three teeth and two fist-size stone tools from the caves, are the strongest evidence yet that the ancestors of modern humans began their out-of-Africa odyssey cons earlier than the textbooks say. The Longgupo fossils are 1.9 million years old, according to three dating techniques; they come from an era when our ancestors supposedly lived only on the continent where they originated--Africa. If the date holds up, "these fossils will be older than any other human remains in China, and the tools will he the oldest artifacts in Asia," says Ciochon.
In science, superlatives are always good for a headline, but the significance of these fossils goes beyond age. The teeth are more primitive than those of Homo erectus, the species to which the famous Java man and Peking man belong. Erectus is also the first human ancestor thought to have left Africa. The fossils do resemble Homo habilis, who appeared 2.5 million years ago in Africa and was the first toolmaker. "It wasn't Homo habilis, and it wasn't Homo erectus, but some other pre-erectus species of Homo," says Ciochon. "Right before 2 million years ago, Homo spread out of Africa."
As surprising as the antiquity of the bones are the stone tools. A pillar of anthropology has been that early humans could not have embarked on an intercontinental trek without advanced implements. But the Longgupo hardware-similar to tools found at Homo habilis sites in Africa more than 2 million years old--implies that knowing how to use stones to bash nuts and crush bones for marrow was quite sufficient to get up and go.
The Longgupo finds are what archeologist Roy Larick of the University of Massachusetts calls "the capstone" of four recent discoveries. A 1.8 million-year-old site in Dminisi, Georgia, discovered in 1991; an infant skull from Indonesia dated last year at 1.8 million years; two sites in Spain as old as 1.6 million years--all suggest that human ancestors were infected with early wanderlust. Although there is little doubt that humankind's deepest evolutionary roots are sunk in the African soft, the branches of the family tree were not confined to a single continent. The conventional view holds that Homo habilis evolved into erectus only in Africa, then wandered into the Mideast and Asia. But Ciochon suspects that some early Homo species left Africa and evolved into Homo erectus in Asia (diagram). It is even possible that any Homo species that did not leave Africa did not evolve into erectus at all. Why, then, are Homo erectus fossils found in Africa? Perhaps some clans of erectus, says Ciochon, walked back.
Such speculation is a bit much for some other scholars. Philip Rightmire of Binghamton University in New York points out that "the Longgupo remains are pretty scrappy. This would not be the material on which I'd construct any bold new theory of human evolution. If I had to bet, I would say this is just another Homo erectus." And as E Clark Howell of the University of California, Berkeley, points out, "we don't even have evidence that pre-erectus Homo dispersed across Africa," let alone Asia.
What the Longgupo fossils say about the evolution of our own species, Homo sapiens, is even more ambiguous. The most popular theory is that sapiens evolved once, in Africa. They spread into Asia and Europe about 100,000 years ago and replaced (anthro-speak for "wiped out") Homo erectus populations that preceded them. Or, Homo sapiens may have evolved many times in many places, from all the Homo erectus clans spread across the Old World. The Longgupo finds strengthen the theory that sapiens evolved only in Africa: given the vagaries of natural selection, it is highly unlikely that each Homo erectus clan, separated from the others for millennia, evolved into the identical descendant species. But as usual, only more fossils can provide a definitive answer. The science of human origins has never been blessed by much Consensus, and the Longgupo fossils continue that fine tradition.
The earliest human ancestors evolved in Africa, beginning about 4 million years ago. What happened netx remains a bone of contention.
Homo habilis, the first toolmaker, evolved in Homo erectus about 1.5 million years ago in Africa. Later, erectus wandered into the Mideast, Southeast Asia and eventually the Far East.
Newly discovered fossils suggest that early Homo species similar to habilis left Africa before 2 million years ago, wandered into Asia and their evolved into Homo erectus. Later, Homo erectus returned to Africa.