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The reconstruction corrects distortions in Touma?'s fossilised skull

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Experts are a step closer to answering whether an ancient skull from
Africa belonged to a possible human ancestor or was closer to apes,
Nature reports.
Fresh fossil finds from Chad in central Africa, as well as a new
analysis of the skull, seem to confirm "Touma?" was closer to us, say
researchers.

The Touma? skull was unearthed in Chad in 2002 to international
acclaim.

But rival researchers attacked claims by the discoverers that it was
the oldest hominid, or human-like creature.

 It may well have given rise to bipedal hominids, but it's not yet a
bipedal hominid

Martin Pickford, National Museum of Natural History

The near-complete skull, pieces of jawbone and several teeth unveiled
in 2002 were discovered in the desert of northern Chad by a team led
by Michel Brunet, of the University of Poitiers, France.

At six to seven million years old, Sahelanthropus tchadensis (better
known by its nickname Touma?) dates to about the time where, according
to genetic data, the ancestors of humans and the ancestors of
chimpanzees went their separate evolutionary ways.


Touma? has a mixture of primitive and more modern features

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The find had a puzzling combination of modern and primitive features.
It had an ape-like brain size and skull shape, combined with a more
human-like face and teeth.

It also sported a remarkably large brow-ridge, more like that of
hominids.

But at least one anthropologist argued that the fossil could belong to
an female forerunner of a gorilla.

Now Brunet and colleagues report discovering two new jaw fragments and
the crown of a tooth in the same geographical area as the earlier
fossils.

The authors say their analysis reveals key similarities to hominid
fossils and differences from African apes that support their original
claim that Touma? belongs on the human branch of the primate
evolutionary tree.

Virtual reconstruction

In a separate paper, a team including Brunet and Christoph Zollikofer
of the University of Z?rich in Switzerland, presents a 3D computer
reconstruction of the skull, which had been badly distorted in the
ground.

The team has essentially "unmangled" the skull, and the reconstruction
appears to confirm S. tchadensis shared key features with later
hominids.


The reconstructed shape of the skull suggests it belonged to a hominid

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In addition, the position of the foramen magnum - the hole where the
spinal cord enters - is similar to that in humans but not apes.

This suggests Touma? was bipedal; he walked upright like we do.

"We performed a virtual reconstruction because the skull is heavily
mineralised and distorted. It is impossible to do one by physical
means," Dr Zollikofer told the BBC.

"[The find] is absolutely unique for several reasons. First, because
of its age. Then because of its geographical location. Third, because
it is incredibly complete."

Not swayed

Martin Pickford of the National Museum of Natural History in Paris is
one of those scientists unconvinced by arguments that Touma? is a
hominid.

"What we're saying is that it is an ape-like animal. It may well have
given rise to bipedal hominids, but it's not yet a bipedal hominid,"
Dr Pickford told the BBC.


The original fossil skull was badly mangled

Professor Zollikofer commented: "I would say most of the disagreement
over the fossil came from the fact that it is distorted, so it is
quite difficult to recognise the diagnostic hominid features."

If Touma? really does belong on the human branch of the evolutionary
tree, its discovery calls into question certain assumptions about our
prehistory.

The fossils were found some 2,500km (1,500 miles) west of the African
Great Rift Valley - traditionally seen as humankind's ancestral home
due to the wealth of hominid fossils that have been discovered there.

The discovery of S. tchadensis implies early hominids ranged far wider
from East Africa, and far earlier, than previously thought.

It also suggests that hominids evolved quickly from apes after they
set off on their own evolutionary path.