The first detailed study of the skull of a tiny, extinct human discovered in Indonesia last year shows that it has features consistent with an advanced brain, despite being only the size of a grapefruit. The findings are controversial, since many anthropologists believe brain size matters when it concerns supporting advanced, human behaviors. In other words, larger is thought to be better. A new analysis suggests this may not be true in this case.
In October, Australian and Indonesian scientists introduced the world to the startling remains of chimpanzee-sized humans who lived on the remote Indonesian island of Flores until about 18,000 years ago, coexisting on the planet with modern humans such as us.
The finding posed a scientific paradox: Although its brain is only one-third as large as modern people, this Flores Man showed signs of advanced intelligence. The discoverers found ashes from nearby fires and sophisticated stone tools these miniature humans presumably left behind.
Now a detailed study of the only skull found among all the small bones indicates that such a diminutive head did not belong to some primitive ape-like creature, but contained several features of higher brains.
The analysis appears in the online journal Science Express. Its lead author is Florida State University anthropologist Dean Falk.
"I started out a skeptic, frankly," she said. "I thought we were going to see a little chimpanzee-like brain, and I was wrong. Nothing like this has been seen before. It shows that not only is brain size important, which of course it is, but here we have an instance where organization, internal wiring, is super important."
The researchers could not study the brain directly, since only the hard skull remained, not the soft tissue. But they were able to analyze a cast of the skull's inner surface, which preserves the surface features of the brain, such as its folds and blood vessels.
The mold was not made from the actual, delicate skull itself, but was a virtual, computer image cast based on computerized scans of the skull interior, made at an Indonesian hospital by its discoverers.
The scientists compared the cast to those of skulls of several related primates, including pre-humans millions of years old, modern humans, modern apes, and pygmies.
Ms. Falk says that relative to its overall size, the brain of Flores Man had very large areas associated in living people with hearing, understanding speech, planning and other higher cognitive functions.
"There is nothing in this to contradict interpretations that have been made about sophisticated behavior," she added. "Furthermore, this brain may well be consistent with the hunt, with the use of fire, and with the production of sophisticated tools. I was bowled over, never thought I would see it in a brain this small."
But not everyone is willing to discard brain size as a measure of advancement. Primate skull expert Katerina Semendeferi of the University of California at San Diego says the new research is puzzling.
"I'm still very skeptical in terms of how much that brain was actually capable of doing," she explained. "I would be very skeptical that a species with a brain that is overall that small can have the complexity that modern humans have with a brain that is three times more than that."
Ms. Semendeferi discounts the notion that the Flores Man brain was a miniature version of the modern type, with just as many complex connections of nerves, but proportionately smaller. She says brain cells do not vary much in size among primates of different sizes and assumes that those of Flores Man were not too much tinier, either.
But the new study suggests that these small-bodied creatures might be a case of parallel evolution with modern humans and evolved a relatively advanced brain on their own. This idea contrasts with the proposal in last year's original study that because the species was isolated it shrank from an archaic population that preceded modern humans.
Katerina Semendeferi says more skull samples might help solve the mysteries surrounding this little being.
"Basing a new model on just one situation is a little dangerous," she noted.