Oldest Skeleton in Human Family Tree Surprises Scientists

Oct. 2 -- THURSDAY, Oct. 1 (HealthDay News) -- New details about the oldest skeleton from the human family tree suggest that human evolution was much more complicated than ever imagined.

Fossil remains of "Ardi," a female member of the hominid species Ardipithecus ramidus who lived 4.4 million years ago, do not resemble a chimp, as was long supposed.

Instead, Ardi was a combination of the features of chimps, humans and other creatures.

"Our ancestors didn't come from something that looked like a chimp, and we now have a very good picture of what it was like and what kind of environment it lived in," said Leslea Hlusko, associate professor of integrative biology at the University of California Berkeley. "Our last common ancestor [shared with chimpanzees] was not a monkey but a different primate. It wasn't a human and it wasn't a chimp. It was something else."

Hlusko is one of the researchers publishing a series of 11 articles about Ardi and her environment in the Oct. 2 issue of Science.

"This is earth-shaking. It challenges the simple paradigm that we've had for a long time of our earliest ancestors being very chimp- or gorilla-like," added Jeffrey Laitman, director of the Center for Anatomy and Functional Morphology at Mount Sinai School of Medicine in New York City. "Now we have this odd beast that is tantalizingly closer to the elusive last common ancestor, and already it's showing features that are different than chimps and gorillas, and in some cases closer to humans."

The findings also suggest that chimps and gorillas have followed their own evolutionary path, quite separate from humans.

"This is sort of a declaration of independence for gorillas and chimps. They're not just transitional types of humans," Laitman said.

Fossil remains of Ardi, who weighed about 110 pounds and stood close to four-feet tall, were first discovered in a remote part of northeastern Ethiopia in 1994. She is 1.2 million years older than "Lucy," an Australopithecus, who, until now, was the earliest existing evidence of the path of human evolution.