Newfound skull has scientists rethinking human family tree
Recently found fossils point to just one human ancestor, say researchers. Differences once seen as marks of separate species are just normal variation.
VANO SHLAMOV
/ AFP/GETTY IMAGES
This well-preserved skull from 1.8 million years ago found in the
remains of a medieval hilltop city in Dmanisi, Georgia offers new
evidence that early man was a single species with a vast array of
different looks, researchers said.
In the humid foothills
of the Caucasus Mountains, deep within a carnivore’s bloody lair, an
early human ancestor fought a life-or-death struggle — and lost.
He had entered the den
on a scavenging mission, possibly with several others. Their plan: use a
stone to scrape meat from the bones of freshly killed prey, then flee
before a sabretooth cat or other giant predator caught him in the act.
“It seems that they
were fighting for the carcasses, and unfortunately ... they were not
always successful,” said David Lordkipanidze, a paleoanthropologist and
director of the Georgian National Museum in Tbilisi.
Now, almost two
million years later, the stunningly intact remains of that failed
foraging mission are causing researchers to question the shape of our
ancestral family tree. Most notable among the fossilized relics are a
cranium and jaw of an adult male that together comprise “Skull 5.”
In a paper
published Thursday in the journal Science, Lordkipanidze and colleagues
say skull and four other fossil craniums recovered at the site contain
features previously ascribed to three different species of human
ancestor: Homo habilis, Homo rudolfensis and Homo erectus.
The explanation, they
say, for this is clear: all three species must be one and the same.
Differences once perceived to be the mark of separate species are in
fact the result of normal variation in physical features, age and
gender.
The assertion has
struck a nerve in a field in which some paleoanthropologists complain
that peers are all too quick to classify small or badly crushed fossil
finds as evidence of new species.
“It’s a little like
the emperor’s new clothes,” study co-author Christoph Zollikofer, a
neurobiologist at the Anthropological Institute and Museum in Zurich,
Switzerland, told reporters. “At some point you have to step out of a
given perspective and take a new one.”
Others
say that while the discovery of Skull 5 is a spectacular fossil find,
the authors have failed to convince them that it applies to fossils
recovered in Africa.
Fred Spoor, a
professor of evolutionary anatomy at the Max Planck Institute for
Evolutionary Anthropology in Leipzig, Germany, said he’s not about to
“say goodbye to Homo habilis and Homo rudolfensis.”
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