Indonesian Hobbits are own species, study on brains shows

February 5th, 2007 · 42 Comments

A tiny, hobbit-like human that lived on a remote Indonesian island 18,000 years ago was a member of its own unique species and was not a diseased human, according to a new study of the hominin’s skull.

When discovery of the so-called hobbitâ€”technically known as LB1â€”was announced in 2004, scientists hailed it as a new species: Homo floresiensis.

Other scientists argued the hobbit is a modern human with a genetic disease called microcephaly, which causes the formation of small brains.

The ensuing debate has led to several comparisons between the hobbit’s brain and those of modern microcephalics. Some teams conclude LB1 is diseased; others conclude LB1 represents a new species.

The new study aimed to resolve the debate by defining the brain characteristics that distinguish “normal” modern humans from microcephalics. The authors then determined where the hobbit brain fits.

“LB1 plops right down with normal Homo sapiens,” said Dean Falk, an anthropologist at Florida State University in Tallahassee and the study’s lead author.

“LB1 also has specific features that are derived and advanced and that makes it unique,” she added.

Sorting Brains

Falk’s team first compared 3-D reconstructions of ten normal human brains and nine microcephalic brains.

The models of microcephalics represented males and females, children and adults, and come from all over the world.

“We wanted a really diverse sample,” Falk said.

The researchers found two characteristicsâ€”in addition to small sizeâ€”that distinguish microcephalic brains: The bottom part sticks out in the back, and the region behind the forehead is unusually narrow.

When the team compared LB1 to the diverse sample of microcephalics and normal humans, it most closely fit the model of normal humans.

“It’s not microcephalic,” Falk said. “In fact it’s the opposite. Except for brain size, the features are the antithesis of microcephaly.”

In the study, published in this week’s issue of the Proceedings of the National Academy of Sciences, Falk’s team adds that LB1’s tiny brain size and other brain characteristics “are consistent with its assignment to a separate species.”

Falk’s team also compared the models to a skull from South Africa that a separate research team said resembled LB1; the computer model classified it as microcephalic.

The team was unable to obtain information about another microcephalic skull that a third research team said resembled the hobbit and thus supported the argument that LB1 was diseased, not a new species.

“Unfortunately, we were not able to address that claim,” Falk said.

Unsettled Debate

Robert Martin is curator of biological anthropology at the Field Museum in Chicago and a co-author of two papers that argue LB1 was a diseased modern human.

The new analysis fails to change his stance.

Most important, Martin said, is a discrepancy between his and Falk’s team on the classification of the skull from South Africa, known as Basuto woman.

Martin said his team analyzed the skull with the “exact same methods” used for an analysis of different skulls published by Falk’s team in Science in 2005. The 2005 paper set off the debate between the two research teams.

According to the Martin team’s results, published online last September in the journal Anatomical Record, the brain of Basuto woman, a known microcephalic, was much more similar to LB1 than the current study found.

“That’s what I don’t quite understand,” he said.

Falk said the two teams got different height measurements for the Basuto woman’s skull, which in turn affected their analyses. Falk recently rechecked her team’s measurements and believes they are accurate, she said.

Martin responded that his team’s measurement technique is sound and he is confident that the Basuto woman’s brain is similar to LB1.

He also questioned the Falk team’s inclusion of juvenile microcephalics in their analysis. LB1 was an adult female.

Martin said hundreds of genes can produce a small brain, so “a proper comparison is with microcephalics that survive to adulthood.”

According to Falk, age is irrelevant because microcephalic brains are fully developed by age ten. Her team wanted a diverse sample to “capture anything they might all have in common,” she added.

New Developments?

Richard Potts, the director of the human origins program at the Smithsonian Institution in Washington, D.C., said that studies of brain shape alone will fail to resolve the debate between these research groups.

He said the scientists need to “step outside the black box of the brain they’ve gotten themselves into.”

Although he declined to give specifics, Potts said forthcoming studies on other parts of the skeleton will “make for a compelling story that sides with the Falk camp.”

Falk’s study is “quite convincing the LB1 brain groups with the normal humans. It’s a good example of that,” Potts said.

“At the same time, there’s no way I expect this to be the last word on the brain of LB1.”

Story reposted from NatGeoÂ