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Brain Study Bolsters Case for Smart Bantam Human Species




COURTESY OF KIRK E. SMITH Mallinckrodt Institute of Radiology of Washington University
When scientists announced last fall that they had unearthed bones belonging to a miniature human species, Homo floresiensis, that lived on the island of Flores in Indonesia as recently as 13,000 years ago, the find made front page news around the world. But controversy followed on the heels of those claims. Several paleoanthropologists countered that the small-bodied, small-brained specimen was instead a H. sapiens individual afflicted with a pathological condition known as microcephaly, not a new species. And in late November, the bones were transported to the lab of one such dissenter--Teuku Jacob, a senior Indonesian paleoanthropologist not involved in the original research--despite objections by some members of the Indonesian-Australian discovery team, sparking a heated custody battle.

Last week marked the return of most of the remains to their repository at the Indonesian Center for Archaeology in Jakarta, nearly two months later than promised. Whether Jacob's study of the bones will yield publications in peer-reviewed journals remains to be seen. Meanwhile, researchers writing today in Science report that their examination of the brain morphology of the Flores hominid, represented primarily by a female specimen known as LB1, upholds the new species interpretation.

LB1's gray matter is long gone, so to reconstruct her chimp-size brain, paleoneurologist Dean Falk of Florida State University and her colleagues created a virtual cast of the skull's interior using computed tomography scans (see image). They then compared LB1's endocast with those of great apes, H. erectus, australopithecines (the extinct hominid group to which Lucy belongs), full-sized modern humans, and pygmy and microcephalic modern humans. The results were striking. "The scaling of brain to body isn't at all what we'd expect to find in pygmies, and the shape is all wrong to be a microcephalic," Falk asserts. "This is something new." In terms of the size of the brain relative to the body, LB1 is most like an australopithecine. But her brain shape resembles that of H. erectus. "I thought the Homo floresiensis brain would look like a chimp's," Falk remarks. "I was wrong. There were fancier things on LB1's brain." Those fancier things include expanded frontal and temporal lobes, which in living humans are associated with higher cognitive processes, such as taking initiative and planning in advance.

According to the team, the findings support the hypothesis that LB1 represents a new species closely related to H. erectus, which could either be the direct ancestor of H. floresiensis or a sister species, linked to H. floresiensis by way of a small, as-yet-unknown common ancestor. The results also lend weight to another controversial claim: namely, that the pea-brained H. floresiensis made advanced tools, controlled fire and hunted large, dangerous prey. Skeptics have attributed archaeological signs of these activities in the cave where LB1 turned up to anatomically modern humans--despite the absence of H. sapiens remains at the site--in large part because other comparably small-brained hominids, (the much older australopithecines, for examples) had no such advanced cultural practices. Indications that LB1 was packing an organizationally advanced brain--however small--may force a rethinking of that logic.

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