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Oldest human ancestor unveiled

Ardi the hominid

An artist's impression of Ardi, a hominid species that lived 4.4 million years ago (Source: J H Matternes/AAAS)

The world's oldest and most complete skeleton of a potential human ancestor has been unveiled by an international team of researchers.

Their unprecedented 17-year investigation of 'Ardi', short for Ardipithecus ramidus, is detailed in a special issue of the journal Science.

The 4.4 million-year-old hominid opens up a new chapter on human evolution because "it is as close as we have ever come to finding the last common ancestor of chimpanzees and humans," says project co-director Professor Tim White.

"This is not an ordinary fossil," says White, a paleontologist in the University of California at Berkeley's Human Evolution Research Center. "It's not a chimp. It's not a human."

Instead, he says, "It shows us what we used to be."

Human timeline


Ardi falls somewhere between this still unknown species and 'Lucy', the famous 3.2 million-year-old hominid, also found in Ethiopia, belonging to the genus Australopithecus.



Bones tell story






"Believe me, we've looked for them," says White, who added that the earliest known stone tools date to 2.6 million years ago.

Hominids and apes




Making love, not war

"We now believe that social, instead of environmental, change, led to the species division," says White. "Natural selection involves reproductive success, so Professor Owen Lovejoy of the project suspects that Ardipithecus males were probably pair-bonded to specific females, and may have aided them by gathering and carrying foods."

Such provisioning by males would have favoured those males who could best walk on two feet, according to the researchers, allowing them free hands for carrying food.


The reduction in canine teeth, which Lovejoy calls "weapons of aggression," further suggests that Ardipithecus males were not as physically hostile with each other as larger-canined chimpanzees are today.

Humans not chimps



Professor Alan Walker, a biological anthropologist at Pennsylvania State University who did not work on the project, says that the Ardipithecus fossils "tell us that the anatomy of closely related living species cannot predict the anatomy of their ancestors very accurately."



Tags: anthropology-and-sociology, fossils, evolution, palaeontology