A smoking gun that could snuff out a hot debate over skeletal remains dubbed the "hobbit" is in hand, literally, according to a group of scientists.
Three wrist bones provide key evidence supporting the argument that fossil remains of an ancient, undersized individual represent a new hominin species that walked the Earth with modern humans, say the study scientists.
The wrist bones resemble those in apes more than those in humans, the researchers write in the Sept. 21 issue of the journal Science.
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Until now, most had assumed that we (modern humans) strode the planet with just one other Homo species, the Neanderthals, and when these guys went extinct, we represented the sole-surviving members of the human genus.
Now it seems, we might have hung out with another Homo species.
"Up until [the hobbit remains] were discovered, we thought we were the only ones for at least 30,000 years, because 30,000 years ago Neanderthals went extinct," said lead author Matthew Tocheri, an anthropologist at the National Museum of Natural History in Washington, D.C.
First unearthed in 2003 in the Liang Bua cave on the Indonesian island of Flores, the remains belong to a three-foot-tall (one meter) adult female, who was about 30 years old when she died 18,000 years ago.
Her stature, combined with evidence from other fossils found at the site, paint a picture of a diminutive bipedal individual who used stone tools and fire while hunting the island's pygmy elephants, Komodo dragons and giant rats.
Since the discovery, scientists have debated whether the specimen represents a new hominin species called Homo floresiensis, possibly a dwarfed offshoot of Homo erectus, a human ancestor that lived as far back as 1.8 million years ago.
Critics, including biological anthropologist Robert Martin of the Field Museum in Chicago, say the remains belonged to a human with microcephalia, a pathological condition characterized by a small head, short stature and some mental retardation.
The hobbit's brain was about one-third the size of a modern adult human's brain.
Hands down finding
In the new work, Tocheri and his colleagues analyzed three wrist bones from the hobbit skeleton, technically called Liang Bua 1 or LB1.
The shape and orientation of the bones matched those of non-human apes and were very different from the wrist bones of Neanderthals (Homo neanderthalensis) and modern humans.
For example, the human trapezoid is boot-shaped, while the same wrist bone in LB1 is wedge-shaped.
"Are they a distinct species or are they pathological modern humans?" asks study leader Tocheri. "I think it's pretty clear that this is a smoking gun, that they are not pathological modern humans. Modern human wrists, normal or abnormal, don't look like an otherwise normal chimpanzee wrist."
After considering the new findings, Martin, who doubts the Homo floresiensis theory, said: "I think it's a pathological modern human," meaning it represents one of us, but with a disease.
He said microcephalia, which shrinks human heads, could also have affected the wrist bones (though nobody has tested this idea).
While Martin says he believes the wrist bones of LB1 match those of earlier hominin species, he points out they weren't compared with Homo erectus, for which wrist bones don't yet exist.
In addition, the finding doesn't rule out microcephalia as the cause of the primitive-looking wrist bones, he said.
However, Martin admits many scientists are on the "new species" side of the debate.
"Most of my colleagues believe this is a new species and that the tiny brain is normal, and I just don't accept that," Martin said.
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