This is an artist's rendering of the possible appearance of D4500. (Photo: J.H. Matternes)
(USA TODAY) -- Scientists trying to unravel the origins of humanity mostly study
scraps - some ancient teeth here, a damaged bone there. But now a lucky
research team has uncovered a fossil superstar: the first complete
skull of an early human adult from the distant past.
million-year-old fossil, known as Skull 5, is like nothing seen before.
It has a small brain case and a heavy, jutting jaw, as did some of
humanity's older, more ape-like ancestors. But other bones linked to
Skull 5 show its owner had relatively short arms and long legs, as does
our own species, Homo sapiens. Those who've studied Skull 5 say it also
provides support for the provocative idea that, 1.8 million years ago,
only one kind of early human held sway, rather than the throng of
different species listed in today's textbooks.
"We're not against
the idea that there might have been more than one species at some point
about 2 million years ago," Christoph Zollikofer of the Anthropological
Institute and Museum in Switzerland, who helped analyze the new fossil,
said at a news conference Wednesday. "But we simply say ... we don't have
sufficient fossil evidence."
That's a controversial claim, but no
one is disputing that Skull 5, discovered in pieces in 2000 and 2005 at
the village of Dmanisi in the nation of Georgia, is a treasure. Never
before have researchers found an adult skull of the early Homo family
that was so exquisitely preserved. Scientists have dug up a few other
skulls similar in age and condition to Skull 5, but all belonged to
individuals who were either too old or too young to be very useful
representatives of their species. Skull 5, on the other hand, is a
mature adult - exactly what's needed.
Generally, "you have to wait until humans bury their dead before you
get something as good as this," says George Washington University
paleoanthropologist Bernard Wood, who was not part of the team. Dmanisi,
he says, is "the FAO Schwarz of hominin paleontology."
addition to Skull 5, four other full or partial skulls have been found
at Dmanisi, and all five come from individuals who died within a few
centuries of each other at most. Outside Dmanisi, researchers have
never found a cluster of fairly complete early skeletons from one sliver
of time. That means the Dmanisi skeletons give scientists an
unprecedented look at the full range of anatomy within a single
By analyzing the shape of the Dmanisi skulls, the team
members found that even though they seem to vary widely they're no more
different from each other than the skulls of a group of modern-day
humans or a group of chimpanzees. The parallel suggests that all five
Dmanisi individuals belonged to the same species of early human,
probably Homo erectus, which many scientists think spawned the lineage
that led to us.
Then the team analyzed skull shape among a grab-bag of early-human
species such as Homo habilis and Homo rudolfensis, all known from
fossils from Africa. By some measures these skulls, too, were no more
different from each other than a selection of chimpanzee skulls or a
group of human skulls. So the differences thought to demarcate species
are actually differences within a species, the team reports in this
Other scientists disagree.
Paleoanthropologist Susan Antón of New York University, while praising
the new analysis, says the Dmanisi team didn't compare fossil features,
such as the anatomy around the front teeth, that differ most starkly
between two different species of early humans. So the Dmanisi team's
hypothesis that there was only one lineage is not totally convincing,
Wood also has doubts, but he agrees with the Dmanisi
researchers that they have an exceptional resource on their hands, most
of it still awaiting excavation.
"The fossil is interesting, and
the site is tremendously interesting," he says. "For all we know, it's
going to be the richest early hominin site there has ever been."