Toumai Reconstruction Seems To Confirm Placement In Hominid Lineage
- From: Rich Travsky <" traRvEsky"@hotmMOVEail.com>
- Date: Wed, 06 Apr 2005 19:02:34 -0600
http://www.nature.com/news/2005/050404/full/050404-6.html
The virtual reconstruction of a skull unearthed at the base of the Saharan
dunes in northern Chad may dispel controversy over whether its owner was
human or ape, says a team of palaeoanthropologists.
The skull, nicknamed Toumaï, along with teeth and a lower jaw was excavated
by a team led by Michel Brunet of the University of Poitiers, France. The
find was unveiled in 2002 and dated to about 7 million years ago ...
Some anthropologists disagreed with the researchers' claim that S.
tchadensis is the oldest known member of the hominid lineage, making it more
closely related to us than to other apes. ...
However, new teeth and jaw specimens from the Toros-Menalla site in Chad and
a digital representation of Toumaï's head, reported in this week's Nature,
build on the original findings, says Brunet. "Now it's completely confirmed
that Toumaï is not a chimp, or a gorilla, but a true hominid," he says.
The new teeth samples verify that Toumaï had small canines, alongside large
molars and premolars that had thick enamel. Such a pattern is similar to that
of later members of the human family.
The virtual reconstruction, led by Brunet's colleague Christoph Zollikofer at
the University of Zürich-Irchel in Switzerland, uses a high-resolution
computed tomography, or CT, scan to show what the fossil would look like
without its cracks and other distortions.
"It's a big step forward," says anthropologist Clark Howell of the University
of California, Berkeley. "These people are masterful at what they do."
The reconstruction shows that the opening in the base of the skull through
which the spinal cord passes, called the foramen magnum, is oriented so that
the neck points downwards. But in apes, such as gorillas, the neck point
backwards, explains Dan Lieberman, a palaeoanthropologist at Harvard
University in Cambridge, Massachusetts and a member of Brunet's team.
This means that Toumaï's head balanced on top of its spine, suggesting an
upright walking stance. "The evidence certainly suggests that Toumaï was a
biped," says Lieberman.
However, Milford Wolpoff, an anthropologist at the University of Michigan
in Ann Arbor believes that although Toumaï is related to the common ancestor
of humans and chimps, it is not a hominid. Based on the reconstruction, he
believes the site on the back of the skull where the neck muscles attach
would support huge muscles, similar to those of apes. "This doesn't fit in
the functional range of bipedalism," he says.
Lieberman, on the other hand, points out that all of the earliest known
bipeds, such as the hominid Australopithecus afarensis, which is about half
as old as Toumaï, had large neck muscles.
"This work confirms that Toumaï is the earliest and most complete hominid,
and suggests that the earliest hominids were bipedal," claims Lieberman.
"And that's big news."
.
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