quote:Pre-Human Is Linked To Ape Line Creature May Give Hint On Man-Chimp Ancestor
Reuters Friday, March 5, 2004; Page A03
A 6 million-year-old creature that lacked sharp canine teeth for fighting may be the first pre-human to have branched off from the ape line, researchers said Thursday.
The short, small-brained creature may provide a good hint of what the common ancestor of chimpanzees and humans looked like, the researchers said.
Fossil remains of the early hominid were found in Ethiopia three years ago, and it seemed to be a subspecies of a known pre-human, Ardipithecus ramidus. But the scientists found more teeth from a group of the hominids and reclassified it as a distinct species, which they named Ardipithecus kadabba.
"Ardipithecus kadabba may also represent the first species on the human branch of the family tree just after the evolutionary split between lines leading to modern chimpanzees and humans," said Yohannes Haile-Selassie, curator and head of physical anthropology at the Cleveland Museum of Natural History in Ohio, who led the study.
But David R. Begun, an anthropologist at the University of Toronto, questioned this interpretation in an accompanying commentary. Begun said there are too many uncertainties for the three groups of pre-human primates for them to be placed in the same genus. He said the issue can only be resolved with the discovery of more fossils.
His team's report, published in Friday's issue of the journal Science, suggests that the last common ancestor of chimps and humans had long canines used to fight -- something chimps have today, but not humans.
The researchers dug up fossils from at least five individuals who once lived in a wooded environment, now a dry, rocky area in the Afar rift of Ethiopia's Middle Awash region -- a rich source of pre-human remains.
They had enough to determine that it was an upright-standing hominid about the size of a chimpanzee that lived 5.2 million to 5.8 million years ago.
The six new teeth, found at the site in 2002, included an upper canine, premolars from both jaws, and upper molars.
"We see a lot of primitiveness in the teeth," Haile-Selassie said in a telephone interview.
One key characteristic is a self-sharpening function.
"The canine tooth comes across the outside face of the lower premolar and it sharpens that way," said Tim White of the University of California at Berkeley, who worked on the report.
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