By JOSEPH B. VERRENGIA
Scientists working with powerful imaging computers say the spectacular 'Hobbit' fossil recently discovered in Indonesia had distinctive brain features that could justify its classification as a separate - and tiny - human ancestor.
The new report, published Thursday in the online journal Science Express, seems to support the idea of a sophisticated human dwarf species marooned for eons while modern man proliferated.
The new research produced a computer-generated model that compared surface impressions on the inside of the fossil skull with brain casts of modern and ancient humans, as well as chimps and other primates.
Kirk E. Smith / Washington University, St. Louis
The scientists said the model shows that the 3-foot specimen, nicknamed Hobbit, had a brain unlike anything they had seen before in the human lineage. The brain is chimplike in size, about 417 cubic centimeters.
Yet the Hobbit's brain shared wrinkled surface features with the much larger brains of both modern humans and Homo erectus, a tool-making ancestor that lived in southeast Asia more than 1 million years ago. Some of those brain features are consistent with higher cognitive traits.
These brain features coincide with physical evidence of advanced behaviors, such as hunting, firemaking and the use of stone tools, which were found alongside the bones in a cave on the remote equatorial island of Flores. To some, this suggests an organized society of tiny hunters flourished on the island for millennia at a time when modern humans dominated the planet.
'This is a unique creature,' said Florida State University anthropologist Dean Falk, who led the study. 'We found amazing, specialized features across the surface from front to back.'
'These findings are consistent with the kinds of sophisticated behaviors that are hypothesized' for the Hobbit, Falk said, but she stopped short of saying the Hobbit was a tool-maker.
In October, scientists from Indonesia and Australia caused an international sensation with their report of a trove of tiny fossils. As many as eight individuals were represented in layers that were dated from 95,000 to 12,000 years ago. The Hobbit skeleton was the most complete specimen and contained the only skull.
In a project funded by the National Geographic Society, Falk and researchers from Washington University in St. Louis created a three-dimensional computer model of the brain using CT scans of the interior of the Hobbit's skull. Known as virtual endocasts, these images show the wrinkles, vessels and other surface features that made faint impressions on the skull's lining.
They compared that model with the brains of chimps, a female Homo erectus, a contemporary woman, a pygmy and a European specimen of a person with a small-brain syndrome known as microcephaly.
Scientists say its brain shape is most closely associated with that of Homo erectus. However, it also reflects some features of modern humans, including:
_A fissure near the back of the brain known as the lunate sulcus, similarly found in the modern human brain. "I almost fell over seeing this feature in something so small," Falk said.
_A swollen temporal lobe, the mid-brain area between the ears where hearing, memory, image identification and emotions are processed.
_A part of the frontal lobe near the eyes that is thought to be involved in planning and initiative-taking.
Such advanced brain features were especially surprising because the rest of the skeleton has more primitive traits like coarse teeth and an apelike pelvis similar to human ancestors that emerged in Africa some 4 million years ago.
"It's a really strange combination of traits," said Michael J. Morwood of the University of New England in Australia, one of the Hobbit's excavators. "It is a new, diminutive human species."
Whether the Hobbit evolved into a dwarfed form of Homo erectus or hails from another, older human cousin is unknown, he said.
Other human evolution specialists were split over the new report.
Katerina Semendeferi of the University of California-San Diego described it as a "cutting edge study." While the Hobbit brain does not fit neatly into an evolutionary pattern, she said it is too much to expect that all species would have brain sizes that would neatly transition in size from ape to modern human.
But some experts dismissed the brain-scan study as "trivial." Primatologist Robert Martin, provost of the Field Museum in Chicago, said the Hobbit probably was a modern human that suffered from a form of microcephaly.
But Falk said the Hobbit brain was quite different from the brain of a modern human with abnormal brain growth, or a human pygmy."
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