Washington
02 October 2009
Anthropologists from around the world have added another million or so years to the history of human evolution. Scientists say the latest fossil find - while not a direct ancestor of modern humans, may offer new insights into the primate family tree.
Probable life appearance of anterior view of Ardipithecus ramidus "Ardi", ARA-VP 6/500 |
Until now, Lucy was believed to have shared a common ancestor with prehistoric apes and to have evolved from there.
But scientists say their new analysis of the older Ardipithecus skeleton suggests that chimps and humans evolved separately from an even older common relative.
Owen Lovejoy is a professor of Anthropology at Kent State University's Biomedical Sciences division in Ohio.
"This was like discovering a time capsule from a period and a place that we knew nothing about," Lovejoy said.
Digital representations of the Ar. ramidus cranium and mandible. This image relates to an article in the 02 October 2009 issue of Science. |
Researchers say the composite skeleton belonged to an adult female who stood 120 centimeters, or four feet tall and weighed about 50 kilograms.
Ardi had elongated palms and special joints and ligaments that allowed it to climb and hang from tree branches. Its bone structure also permitted walking upright on the ground like modern humans. But it lacked the arched feet and smooth gait evident in Lucy and other later hominids.
Researchers say that despite its many ape-like features, Ardipithecus was too different from modern chimps for the lineage to be considered direct.
Definitions from human, left, Ar. ramidus, middle, and chimpanzee, right, all males. Below are corresponding samples of the maxillary first molar in each. |
Tim White, a professor at the Human Evolution Research Center at the University of California at Berkeley says Ardipithecus' mixture of ape and human-like features suggests that our "last common ancestor" may have been much older than anthropologists believe.
"We may have thought that human evolution began somewhat by accident a million years ago with the discovery of tools or 2.5 million years ago with the discovery of the first stone tools," White said. "But in fact, Ardipithecus tells us that we as humans have been evolving toward what we are today for at least six million years."
Partial skeleton of Ardipithecus ramidus, a hominid species living about 4.4 million years ago in Ethiopia. Eleven papers from an international team of authors published in print and online in this special issue describe anatomy of this species. |
Ethiopia regards Ardi's fossil remains as a national treasure, and they are on permanent display at the anthropology museum in Addis Ababa.
The discovery of Ardipithecus is detailed in 11 research papers published this week in the journal Science.