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Archive for Friday, October 2, 2009

Scientists: Before Lucy came Ardi, pre-human ancestor 4.4M years ago

October 2, 2009

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This digitally rendered composite image from the journal Science shows the foot of the “Ardi” skeleton.

This digitally rendered composite image from the journal Science shows the foot of the “Ardi” skeleton.

— Move over, Lucy. A 4-foot-tall female nicknamed Ardi, who lived 4.4 million years ago in Africa, has replaced you as the earliest best known ancestor of the human species.

Ardi’s nearly complete skeleton is 1 million years older than Lucy’s, pushing back the point when hominids — pre-human primates — are known to have split from the evolutionary line that led to chimpanzees and gorillas, an international team of scientists announced Thursday.

“Ardi is not a chimp. It’s not a human. It’s what we used to be,” said paleontologist Tim White, an authority on human evolution at the University of California, Berkeley. White and his colleagues spent 15 years recovering and studying Ardi’s bones before Thursday’s announcement.

Ardi is “on our side of the family tree, not the chimpanzee side,” White told a news conference in Washington sponsored by the journal Science.

Ardi is named for her genus and species, Ardipithecus ramidus, a distant cousin of Lucy’s line, Australopithecus afarensis.

The discovery sheds new light on human evolution during a previously little known epoch. Scientists believe that humans and apes descended from a “last common ancestor,” an even more primitive primate that lived between 7 million and 9 million years ago.

Ardi isn’t the last common ancestor, White said, but “it’s the closest we’ve come to the last common ancestor.”

The first of Ardi’s bones, a single tooth, was discovered in 1992, not far from where Lucy’s skeleton was buried in the fossil-rich Afar Rift of Ethiopia. Later, more than 100 other pieces, including bits of a skull, hand, foot and pelvis, were eased out of the volcanic soil and reassembled.

Ardi probably ate fruit, berries, mushrooms, birds, bats and mice and other small mammals, judging by her teeth and the remains found where she was discovered. Scientists can tell she was female because of the shape of her canine teeth and her pelvis.

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