Re-writing history--again! Associated Press had a slightly different
article discussing "tree vs. bush" geographic spread of our species.
It's looking more and more like a far-reaching tree
*Natalia*
Perfectly preserved 1.8 million-year-old skull 'could re-write history
of human evolution'
Palaeontologists believe finds could re-write early history of
human evolution
by Steve Connor, Science Editor, Fri. Oct. 18/13
http://www.independent.co.uk/news/science/perfectly-preserved-18-millionyearold-skull-could-rewrite-history-of-human-evolution-8887039.html
Scientists have revealed one of the most dramatic discoveries in human
origins with a perfectly preserved fossilised skull of an ape-like man
who lived about 1.8 million years ago.
The discovery, along with the remains of four other individuals who
lived at the same time, in the same place, has generated intense
excitement among palaeontologists who believe the finds could re-write
the early history of human evolution.
The skull and its lower jawbone were found at a palaeontology site near
the medieval town of Dmansi in the foothills of the Caucuses in Georgia,
which has become one of the most important centres for understanding
human origins outside Africa.
A team of researchers has spent the past eight years studying the fossil
skull, which was first excavated in 2005, and its jawbone, discovered in
2000 but only now re-united with its "owner".
The first scientific description of "skull 5", published in the journal
Science, indicates that the adult male had a large, long face, heavy
features, large jaw and teeth but an exceptionally small brain case,
less than half of the size of a typical human today and not much bigger
than a gorilla's brain.
The four other skulls are thought to have belonged to an elderly,
toothless male, another adult male, a young female and an adolescent of
unknown sex. The scientists do not know whether they were part of the
same family group or had lived at precisely the same time.
Dating technology based on argon isotopes found that they lived between
1.77m and 1.85m years ago. The site was next to a river where big game
and fierce predators made frequent encounters - bones of large
saber-toothed cats and an extinct giant cheetah have also been found
alongside those of large herbivores.
All five skulls were unearthed from what were probably underground dens
where the large carnivores had dragged their prey. These had collapsed
soon afterwards, which had helped to preserve the animal and human
remains in good condition.
"Dmansi is a unique snapshot of time - maybe a time capsule that
preserves things from 1.8 million years ago," said Professor David
Lordkipanidze of the Georgia National Museum in Tblisi, the lead author
of the study.
"This was a place where was big competition between carnivores and
hominins [ancient humans]. It seems that they were fighting for the
carcasses, and unfortunately for the hominins, but fortunately for us,
they were not always successful," Professor Lordkipanidze said.
What has surprised the scientists is the range of physical variation
between the five individuals. This has led them to suggest that several
other early human species living at about the same period in Africa may
in fact all belong to the same species.
"Had the braincase and the face of skull 5 been found as separate
fossils at different sites in Africa, they might have been attributed to
different species," said Christoph Zollikofer, a neurobiologist at the
Anthropological Institute and Museum in Zurich.
"The [five skulls from Dmanisi] look quite different from one another,
so it's tempting to publish them as different species. Yet we know that
these individuals came from the same location and the same geological
time, so they could, in principle, represent a single population of a
single species," Professor Zollikofer said.
Despite their anatomical differences, 3-D modelling of the five skulls
shows that they would only have been as physically varied as any five
individuals chosen at random from a population of either modern humans
or chimpanzees.
"Thanks to the relatively large Dmanisi sample, we see a lot of
variation. But the amount of variation does not exceed that found in
modern populations of our own species, nor in chimps and bonobos,"
Professor Zollikofer said.
"Furthermore, since we see a similar pattern and range of variation in
the African fossil record, it is sensible to assume that there was a
single Homo species at that time in Africa," he said.
"And since the Dmanisi hominids are so similar to the African ones, we
further assume that they both represent the same species," he added.
The scientists suggest that the Dmanisi individuals probably belonged to
Homo erectus, the first human species to emerge from Africa, and that
certain African species such as Homo habilis, which had lived earlier
than H. erectus, may actually be the same species as Dmanisi man.
Ian Tattersall of the American Museum of Natural History in New York
told Science that the latest, fifth skull from Dmanisi is "undoubtedly
one of the most important ever discovered", while Tim White of the
University of California, Berkeley, described it simply as "an iconic
fossil".
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