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Fossil find may be 'missing link'

The fossils were found at Bouri, north-east of Addis Ababa. The international team of researchers who made the discovery suggest the remains could even come from a creature that immediately preceded humans.

This is a contentious claim among scientists who have competing theories as to how humans first emerged in history.

However, there are three pieces of evidence at Bouri: new skull and tooth fragments, tools for carving and eating meat and both long arm and leg bones.

If these can all be shown to have come from the same creatures - which has not been achieved yet - then a vital missing link in the evolution of humans from apes may well have been found.

The reasoning is that the oldest fossils of a direct human ancestor are 1.7 million years old. Homo erectus used tools and had short arms and long legs. The youngest human-like ape fossils show long arms and short legs, and no evidence of technology.

The new discovery may sit between the two in time and evolution.

Whatever the connection between the various finds at Bouri, the tools are the earliest examples ever found of technology being used to eat meat and scrape marrow out of bones.

The scientists have called their new hominid Australopithecus garhi, after the local word for "surprise". From anatomical analyses and measurements they argue A. garhi is quite distinct from A. africanus and from the other hominid species known to be alive around the same time.

"What we found was a cranium on a hillside, two and a half million years old, having a small brain case, a very projecting face, and very large, back teeth," says Professor Tim White from the University of California-Berkeley who co-led the team with Berhane Asfaw of Ethiopia's Rift Valley Research Service.

"This is a combination never seen before in a fossil species of hominid."

The difficulty is establishing the significance of A. garhi in terms of human evolution.

"You go into this period with, in essence, bipedal, big-toothed chimps, and come out with meat-eating large brained hominids," says Professor White. "That's a big change in a relatively short time."

The inclusion of meat and bone marrow in the diet could be a key factor, providing the extra nutrition required to evolve bigger brains.

Many paleoanthropologists will need more evidence to be convinced. For a start, the Bouri limb bones may not necessary be those of A ghari.

The research is published in two separate papers in the journal Science.

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