Flores Hominid In her younger days.
Posted on 03/05/2005 5:36:12 AM PST by Lessismore
The startling announcement last October of an 18,000-year-old skeleton of a new species of human posed a paradox: Despite having a brain no larger than a chimp's, the diminutive hominid from the Indonesian island of Flores showed signs of advanced intelligence, including hunting with sophisticated stone tools. That paradox may now be solved. A detailed study of the cranium of Homo floresiensis, published online this week by Science (www.sciencemag.org/cgi/content/abstract/1109727), reveals that the hominid apparently managed to pack a number of features of more advanced brains into its very small skull. Brain features preserved in its cranium suggest that the Flores hominid may have been able to perform advanced cognitive tasks, says lead author Dean Falk of Florida State University in Tallahassee.
That finding may overturn long-held ideas about the evolution of the human brain and also raises some provocative notions about how the Flores people evolved in the first place. "If they are correct, this is really a stunner," says anthropologist Leslie Aiello of University College London (UCL). Evolutionary anatomist Fred Spoor, also of UCL, adds that the new study "upsets one of our main concepts of human evolution, that brain size has to increase for humans to become clever." The work also undercuts the notion proposed by some critics that the Flores bones are those of a microcephalic modern human rather than of a new species.
To study the hominid's brain, Falk and colleagues, including anthropologist Charles Hildebolt of the Mallinckrodt Institute of Radiology in St. Louis, Missouri, analyzed a cast of the inner surface of its skull, or endocast, which preserves the surface features of the brain. Because the skull was too fragile for the usual method of pouring liquid rubber inside it, the team made a virtual endocast from computerized tomography scans. The original discovery team, including co-authors Michael Morwood and Peter Brown of the University of New England in Armidale, Australia, had the skull scanned at a hospital in the Indonesian capital of Jakarta before the bones were temporarily moved last fall to Yogyakarta (see sidebar).
The researchers compared the endocast to virtual endocasts of the skulls of a microcephalic modern human, a modern woman, a Homo erectus, a pygmy, and a chimpanzee, as well as latex endocasts of other humans, primates, and extinct hominids. They found that, relative to its overall size, the brain of Homo floresiensis has very large temporal lobes, brain regions associated in living people with understanding speech and hearing. Even more dramatically, the hominid has highly folded and convoluted frontal lobes, areas of the brain just under the forehead that are implicated in higher cognition. "There are two huge convolutions," Falk says. "I haven't seen swellings like this before in any [extinct] hominid endocasts," including those of Homo erectus. The most convoluted region is in the most forward-projecting part of the frontal lobe, called the frontal pole. Falk identifies this region as Brodmann's area 10, which is expanded in modern humans and is involved in undertaking initiatives and planning future actions--key components of higher cognition. This enlarged area suggests that the little Flores people may well have been capable of creating the stone tools that were found near them, which are more typical of those made by prehistoric modern humans than earlier hominids including Homo erectus. "The real take-home message here is that advanced behaviors, like making sophisticated stone tools, do not necessarily require a large, modern, humanlike brain," says Spoor. "It can be done by reorganizing a small brain, with convolutions and rewiring, and this goes to the heart of our understanding of human evolution."
Not everyone is ready to discard the importance of brain size, however. Anthropologist Katerina Semendeferi of the University of California, San Diego, who has studied area 10 extensively, cautions that "many would argue that absolute size is of paramount importance"; she adds that stronger evidence linking the stone tools with the small Flores people would strengthen the case for their cognitive abilities.
Whatever the hominid's capabilities, the endocast results argue against the notion that it was a pathological case of microcephaly, the authors say. In overall brain shape, the Flores hominid least resembles the microcephalic, and it also bears little resemblance to the pygmy. "The skull is totally the wrong shape" to be a microcephalic, Falk says. But anthropologist Alan Thorne of the Australian National University in Canberra counters that the single European microcephalic analyzed "tells us virtually nothing about the global range of microcephalic virtual endocasts." Others agree that the paper alone does not completely rule out microcephaly. "The case [against microcephaly] is increasingly less likely but not entirely closed," says Aiello. Spoor notes, however, that few researchers are convinced by the microcephaly argument at this point. "Colleagues advocating that [the Flores hominid] is a modern human microcephalic should start publishing hard evidence in peer-reviewed journals to underpin their claims," he says.
Assuming that Homo floresiensis is a new hominid species, the question remains why its brain is so small. In the original Nature papers, Morwood, Brown, and their co-authors suggested that an ancestral population of larger Homo erectus shrank in body and brain, in the first case of island dwarfism seen in hominids. But the new paper urges reconsideration of an alternative hypothesis, that a small-brained, small-bodied, pre-erectus hominid managed to get to Flores in the distant past, and then, in a case of parallel evolution with modern humans, evolved a relatively advanced brain on its own. "Some of [the hominid's] traits indicate that the ancestral population may predate Homo erectus," says Morwood. He adds that his team is now preparing to look for just such an ancestor on the Indonesian islands of Java and Sulawesi. Says Falk: "Maybe there are even more surprises waiting out there."
good things come in small packages... pong
It couldn't perhaps be that inbreeding accounted for this "new" species...after all, wouldn't the gene pool on that island have been rather small?
During the last glacial period the oceans were several hundred feet lower and this island was much larger.
In fact, all of the area between Australia and the mainland continent may have consisted of a broad savannah or forest, with today's Indonesian islands as mountain ranges..
These hominids may be part of ancestral myths about "little people"..
Contrary to today's Disneyfied portrayal of such characters as cute, shy, freindly and only a bit mischievious, the old tales portray the little people as mean spirited, sadistic, and extremely dangerous..
Oral traditions of survivors from that area's end of the Ice Age and subsequent flooding may have come through to our time..
I had the opportunity to study paleoanthropology, but it conflicted with my dream of becoming a scientist.
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