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Ancient Skeleton Could Rewrite the Book on Human Origins

It was not until Thursday, after a decade and a half of work in the field and the lab, that White and his colleagues produced the first comprehensive analysis of the new species. The original fossils are being housed in a museum in Ethiopia.

"It's just a treasure-trove of surprises," Lovejoy said.

The origin of the human species via evolution from earlier primates is beyond scientific dispute. Field work over the past century has shown that the human line originated in Africa, and the fossil findings have been bolstered by laboratory analysis of the genetic codes of humans, chimpanzees and other primates. The fine details of human origin, however, become sketchier, and more subject to interpretation and debate, as the researchers dig deeper into the past and the fossils become scarcer.

Scientists continue to search for the "last common ancestor," sometimes abbreviated as the LCA. This is the creature to which both modern humans and modern chimpanzees can trace their ancestry. Many scientists think the common ancestor lived at least 7 million years ago. The new research on Ardi suggests that this ancestor didn't look nearly as much like a modern chimpanzee as had been previously suspected. Rather, the ancestor would have looked more like Ardi. This suggests that chimpanzees, far from being time machines for visiting the distant past, have themselves evolved significantly, including developing such skills as suspending from branches and knuckle-walking.

"The common ancestor looked like Ardi. It's the chimp and gorilla that have evolved enormously, not hominids. Hominids have concentrated their evolution in two things -- upright walking and brain. Everything else is pretty primitive," Lovejoy said.

In Ardi's species, the males are not significantly different in size from the females. The males also lack the dagger-like teeth that male chimps use to fight one another for access to ovulating females. Lovejoy argues that this is a sign of a different social organization. The males, he argues, pair-bonded with females. Lovejoy sees male parental investment in the survival of offspring as a hallmark of the human lineage.

David Pilbeam, a Harvard paleontologist, noted that there has been some impatience in the scientific community as White and his team conducted the analysis of the new species, but he suggested that the wait was worth it: "This is an extraordinary achievement, of discovery, recovery, reconstitution, description and analysis, which will keep many others busy for at least another 15 years."

Ardi did not look like a human by any stretch. And there is no way to read her mind and measure her sense of self, her awareness of her place in the universe. But if the scientists are correct, her path in life proved to be fruitful over time, and the planet witnessed the rise of a new animal that could run on two legs, invent tools, tame fire, and perhaps eventually -- with much digging and scraping -- decipher its own origin.

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