The human family tree just got shaken to its roots. A 7-million-year-old skull, unearthed in a Central African desert, has been identified as the remains of humankind's oldest known ancestor.
The crumbling, thick-browed skull is 3 million years older than any previously known hominid skull. Anthropologists say the discovery promises to have far-reaching impact on current theories of human origins. "These discoveries strongly shake our conceptions of the earliest steps in hominid history," says Michel Brunet, the French anthropologist who reported the discovery in the current issue of the British journal Nature. It suggests that hominid species may have been more varied than once thought, and may have diverged from the apes earlier than previously suspected. The skull, discovered in the remote Djurab desert of northern Chad, combines an ape-like brain case with teeth and a prominent brow that are distinctly human. Brunet says it appears to date from the time when humans and chimpanzees diverged from a common ancestor. The features are a "unique mosaic" of primitive and human-like characteristics, he says --- an entirely new species, Sahleanthropus tchadensis, that differs markedly not only from apes but from other hominid species as well. Researchers named the male creature Toumai, which means "hope of life" in the Goran language of Chad. "Toumai is arguably the most important fossil discovery in living memory, rivaling the discovery of the first 'ape-man' 77 years ago," says Henry Gee, Nature's paleontology editor. Brunet's 40-person scientific team didn't find enough of Toumai to determine whether he walked upright. But he says the location of the discovery and its age suggest that pre-human ancestors may have been widespread in Africa 7 million years ago --- and that humans and chimpanzees may have diverged on different evolutionary paths earlier than suspected. "The next skull we have is 4 million years later, so we don't know what happened in between," Brunet says. "This is just the beginning of our knowledge of the human lineage." Although the next-oldest hominid skull is 3.5 million years old, researchers have, in the last year, found signs of earlier hominids in Africa's Rift Valley --- including 5.8-million-year-old teeth and bones in Ethiopia. Researchers have also reported finding the remains of a 6-million-year-old hominid in Kenya, though the discovery is disputed. The newly discovered skull contains a mixture of human- and ape-like features that suggests scientists might be getting closer to the hypothetical "missing link" --- the common ancestor of apes and humans --- but some experts say the discovery also implies that human ancestry may be more complicated than anyone thought, perhaps more like an unruly bush than the limbs on some neatly branched "tree." "The popular image of a neat line to humans from our common ancestor with chimps is seriously misleading," says George Washington University anthropologist Bernard Wood. "A hominid of this age should only just be beginning to show signs of being a hominid," he says. "It certainly should not have the face of a hominid less than one-third its geological age. It plays havoc with the tidy model of human origins." Wood says the discovery implies that numerous species of hominids, already distinct from chimpanzees and other apes, may have populated Africa between 5 million and 10 million years ago --- and that pre-human ancestry may have been more diverse than the traditional view of human evolution. Since fossils from that long ago are rare and often fragmentary, Wood says the latest discovery only hints of a "huge and hitherto unsuspected diversity of ancient fossil hominids." Based on the skull, Toumai was a male about the size of a modern chimpanzee, but resembled neither chimps or known hominids. The six fragments of skull and jaw were unearthed by French and Chadian scientists from a layer of ancient sandstone in what Brunet says is now "flat monotonous desert interrupted by occasional dunes." From other fossils found at the site, however, the researchers say when Toumai roamed the region, it was close enough to a lake to support at least 24 primitive species of mammals, including elephants, three-toed horses, giraffes, antelope and hippopotamuses. The location of the discovery also breaks traditional molds of human ancestry. Until now, the earliest hominid fossils have been found in Ethiopia and Kenya. The Chadian site is more than 1,500 miles west of the hominid fossil-rich Rift Valley. Until now, many scientists have believed that upright-walking pre-humans evolved only on the east side of the rift. Brunet says the latest discovery clearly shows that human origins weren't limited to East Africa. "It will never be possible to know precisely where or when the first hominid species originated," he said. "But more surprises can be expected." http://www.accessatlanta.com/ajc/epaper/editions/today/news_d3d222d7b155b02400fa.html ______________________________________________________________________ Signup for the Fusion Authority news alert and keep up with the latest news in ColdFusion and related topics. http://www.fusionauthority.com/signup.cfm Archives: http://www.mail-archive.com/[email protected]/ Unsubscribe: http://www.houseoffusion.com/index.cfm?sidebar=lists
