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Monday, January 26, 2009

"Hobbits" Were Separate Species, Skull Suggests

January 23, 2009

The skull of the so-called hobbit discovered on the Indonesian island of Flores in 2003 suggests its owner was an archaic human ancestor, not a diminutive or diseased modern human, according to a new study.

(Read "The People Time Forgot: Flores Find" in National Geographic magazine.)

The conclusion stems from a comparison of the skull to the noggins of modern humans and apes, as well as the fossil brain cases of early human ancestors.

"The shape of the skull is consistent with what we would expect for a small archaic Homo," said Karen Baab, a biological anthropologist at Stony Brook University in New York State. The genus Homo includes modern human beings as well as close relatives like Neanderthals and Home erectus.

Baab is the lead author of the study, published online in the Journal of Human Evolution.

(Related: Flores hobbit-like human picture gallery.)

Heady Debate

The paper is the latest volley in the debate over what, exactly, the tiny, 18,000-year-old fossils represent.

The hobbit, which was about the size of a modern three-year-old child, was originally hailed as belonging to a heretofore unknown species, Homo floresiensis. (Related: "'Hobbit' Human Was Unique Species, Wrist Bones Suggest" [September 20, 2007].)

Skeptical scientists have offered alternative identifications, suggesting, for example, that the hobbits were diminutive modern humans with a genetic disease that causes small brains, called microcephaly.

(Related: "'Hobbit' Humans Were Diseased Cretins, Study Suggests" [March 6, 2008].)

Abnormal or Just Uneven?

The new research focuses on the asymmetry—or unevenness—between the left and right sides of the hobbit's skull.

A paper published in 2006 concluded the skull is highly asymmetrical, consistent with abnormal development—a condition that would invalidate use of the skull to represent a new species.

The new study also finds the skull asymmetrical, but within the range of healthy human ancestors.

What unevenness exists, Baab said, can at least partially be explained by the process of fossilization.

Robert Eckhardt is a professor of developmental genetics and evolutionary morphology in the kinesiology department at Pennsylvania State University and co-author of the 2006 paper.

In an email, he dismissed the fossilization explanation and said the marked asymmetry "is strong evidence for developmental abnormality."

Robert Martin is the curator of biological anthropology at the Field Museum in Chicago, Illinois. He said, though the paper examines skull shape and size, it ignores the tiny, asymmetrical brain, which could be seen as evidence of microcephaly.

"Why does this individual have such a tiny brain?" he said.

"If it was three million years old, it wouldn't be a problem. The problem is it is only 18,000 years old and it sticks out like a sore thumb."