Before conducting his hobbit study, Tocheri had found that a particular wrist bone is wedge-shaped in great apes and early human ancestors but is squared-off in modern humans and Neandertals.
That wrist bone in the hobbit retains the wedge shape, he found.
"It was a no-brainer from my perspective," Tocheri said of his conclusion that the hobbit is its own species.
Chris Stringer is a research leader in the Human Origins program at the Natural History Museum in London. He said the study makes a convincing case that the wrist bones are primitive.
The research also supports previous studies that identified primitive shoulder joints and jawbones in the hobbit, as well as unpublished reports of primitive features in the foot.
"When you put all this together, you do end up, I think, strongly reinforcing the idea that this is indeed a very strange and very primitive kind of creature, not necessarily [in the genus Homo]," Stringer said.
"Obviously, one has to temper this with admitting that we still need more material."
More Bones to Pick?
Robert Martin is curator of biological anthropology at the Field Museum in Chicago and co-author of two papers arguing the hobbit is a diseased modern human. He said that possibility remains despite the new findings.
While the hobbit's wrist bones do appear primitive, Martin noted, the study fails to include a direct comparison of the hobbit's wrist to those of a modern human with microcephaly.
Microcephaly is the bone disorder that he believes afflicts the hobbit. The disorder also causes deformations elsewhere in the skeleton, potentially even the wrist bones.
"I stick to the suggestion that [the hobbit] is more likely to be a pathological modern human than any kind of new hominid species," he said.
Tocheri and colleagues write in their paper that no known genetic disease, including microcephaly, results in a wrist that looks like the hobbit's or those of other early human ancestors.
Nevertheless, the mystery of what exactly the hobbit is and how it wound up on the island of Flores remains unresolved.
(See a National Geographic magazine feature: "Flores Find: The People That Time Forgot.")
Researchers need as-yet unavailable wrist bones from Homo erectus to determine if the modern wrist morphology was present in modern human's closest direct ancestor.
Such information will help clarify whether the hobbit is a Homo erectus that shrunk to dwarf size on the isolated Indonesian island or is a new species.
"The fact that the [wrist bones] align themselves so clearly with ape morphology is pretty interesting," said Campbell Rolian, a graduate student of anthropology at Harvard University.
"And [it] is really just another feather in the cap of those who are willing to ascribe it to a new species."
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