MAGALIESBURG, South Africa (AP) —
Scientists say they've discovered a new member of the human family
tree, revealed by a huge trove of bones in a barely accessible,
pitch-dark chamber of a cave in South Africa.
The creature
shows a surprising mix of human-like and more primitive characteristics —
some experts called it "bizarre" and "weird."
And
the discovery presents some key mysteries: How old are the bones? And
how did they get into that chamber, reachable only by a complicated
pathway that includes squeezing through passages as narrow as about 7½
inches (17.8 centimeters)?
The
bones were found by a spelunker, about 30 miles (48 kilometers)
northwest of Johannesburg. The site has yielded some 1,550 specimens
since its discovery in 2013. The fossils represent at least 15
individuals.
Researchers
named the creature Homo naledi (nah-LEH-dee). That reflects the "Homo"
evolutionary group, which includes modern people and our closest extinct
relatives, and the word for "star" in a local language. The find was
made in the Rising Star cave system.
The
creature, which evidently walked upright, represents a mix of traits.
For example, the hands and feet look like Homo, but the shoulders and
the small brain recall Homo's more ape-like ancestors, the researchers
said
Lee Berger, a professor at the
University of the Witwatersrand in Johannesburg who led the work, said
naledi's anatomy suggest that it arose at or near the root of the Homo
group, which would make the species some 2.5 million to 2.8 million
years old. The discovered bones themselves may be younger, said Berger,
an American.
At a news
conference Thursday in the Cradle of Humankind, a site near the town of
Magaliesburg where the discovery was made, bones were arranged in the
shape of skeleton in a glass-covered wooden case. Fragments of small
skulls, an almost complete jawbone with teeth, and pieces of limbs,
fingers and other bones were arrayed around the partial skeleton.
Berger
handed a skull reconstruction to Deputy President Cyril Ramaphosa, who
kissed it, as did other VIPs. Berger beamed throughout the unveiling.
The
researchers also announced the discovery in the journal eLife. They
said they were unable to determine an age for the fossils because of
unusual characteristics of the site, but that they are still trying.
Berger
said researchers are not claiming that neledi was a direct ancestor of
modern-day people, and experts unconnected to the project said they
believed it was not.
Rick Potts, director of the
human origins program at the Smithsonian Institution's Natural History
Museum, who was not involved in the discovery, said that without an age,
"there's no way we can judge the evolutionary significance of this
find."
If the bones are about
as old as the Homo group, that would argue that naledi is "a snapshot
of ... the evolutionary experimentation that was going on right around
the origin" of Homo, he said. If they are significantly younger, it
either shows the naledi retained the primitive body characteristics much
longer than any other known creature, or that it re-evolved them, he
said.
Eric Delson of Lehman
College in New York, who also wasn't involved with the work, said his
guess is that naledi fits within a known group of early Homo creatures
from around 2 million year ago.
Besides
the age of the bones, another mystery is how they got into the
difficult-to-reach area of the cave. The researchers said they suspect
the naledi may have repeatedly deposited their dead in the room, but
alternatively it may have been a death trap for individuals that found
their own way in.
"This stuff
is like a Sherlock Holmes mystery," declared Bernard Wood of George
Washington University in Washington, D.C., who was not involved in the
study. Visitors to the cave must have created artificial light, as with a
torch, Wood said. The people who did cave drawings in Europe had such
technology, but nobody has suspected that mental ability in creatures
with such a small brain as naledi, he said.
Potts said a deliberate disposal
of dead bodies is a feasible explanation, but he added it's not clear
who did the disposing. Maybe it was some human relative other than
naledi, he said.
Not
everybody agreed that the discovery revealed a new species. Tim White of
the University of California, Berkeley, called that claim questionable.
"From what is presented here, (the fossils) belong to a primitive Homo
erectus, a species named in the 1800s," he said in an email.
At the news conference in South Africa, Berger disputed that.
"Could this be the body of homo erectus? Absolutely not. It could not be erectus," Berger said.
___
By LYNSEY CHUTEL and MALCOLM RITTER reported from New York.AP
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