Thursday, October 13, 2005

ENV: More little jawbones

A Big Debate on Little People: Ancient Species or Modern Dwarfs?
By JOHN NOBLE WILFORD, The New York Times, October 12, 2005


New discoveries in a cave on the Indonesian island of Flores, notably another jawbone, appear to give additional support to the idea that a separate species of little people new to science and now extinct lived there as recently as 12,000 years ago.

But a vigorous minority of skeptical scientists were unmoved by the new findings. They contend that the skeletal remains are more likely to be deformed modern human beings, not a distinct species.

The group of Australian and Indonesian researchers who announced the first findings a year ago and proclaimed the new species Homo floresiensis describe the additional bones in a report to be published tomorrow in the journal Nature.

They said the bones were fragments of nine individuals of unusually small stature, little more than three feet tall, and, judging by one skull, with brains the size of a chimpanzee's. The newly discovered lower jaw was almost identical to one previously found, except that it appeared to be 3,000 years younger.

"We can now reconstruct the body proportions of H. floresiensis with some certainty," the scientists, led by Michael J. Morwood and Peter Brown, both of the University of New England in Australia, said in the report.

"The finds further demonstrate," they continued, that the original skull and partial skeleton was not from "an aberrant or pathological individual, but is representative of a long-term population" that was present during the period from 95,000 to 12,000 years ago.

The implication that made the original discovery a year ago such a sensation was that these "little people of Flores," as they are commonly called, represent a distinct species that shared the earth with modern humans far more recently than anyone had supposed.

In a commentary in the journal, Daniel E. Lieberman, a biological anthropologist at Harvard University, said, "All in all, it seems reasonable for Morwood and colleagues to stick to their original hypothesis that H. floresiensis is a new species."

But Dr. Lieberman noted that the authors were less certain of the new species' lineage than they had been a year ago. Then the discovery team speculated that the little people had evolved from Homo erectus, the immediate predecessor of Homo sapiens. Now they suggest in the report that the species may descend more directly from earlier members of the human family, like the australopithecines, the group the famous 3.2-million-year-old Lucy belonged to.

In an exchange of e-mail messages from Australia, Dr. Brown said, "The limb proportions, stature, brain size and skeletal robusticity of H. floresiensis replicated those in Australopithecus afarensis, not in any member of our genus Homo."

Dr. Brown said he was preparing to publish results of research that could explain what, if any, connection the little people had to Lucy.

But some paleontologists and biologists express strong doubts that the little people represent a new species. Two separate groups, including Indonesians, Australians, Americans and Britons, said this week that they were about to submit reports to a journal that they say refute the new-species hypothesis.

"I don't think anything is changed with this paper," Robert D. Martin, a biological anthropologist and provost at the Field Museum in Chicago, said in a telephone interview, referring to the latest Nature report. "I feel very strongly that these people are glossing over the problems with this interpretation."

In Dr. Martin's view, in which he is joined by several prominent scientists, the more likely explanation for the small stature is, in part, a phenomenon known as island dwarfing. People and animals living in isolation for many generations tend to evolve smaller bodies, their growth constrained by limited resources.

Dr. Lieberman, who wrote the commentary in Nature, said the dwarfing issue could be resolved if fossils of much earlier specimens of the Flores people were discovered.

"If the island-dwarfing hypothesis is correct," he wrote, "then the island's earliest inhabitants should be larger than the Liang Bua fossils."

Liang Bua is the cave at a remote Flores village where archaeologists found the first bones of the little people two years ago. Besides the skull and jaw, the bones included limbs and other fragments in deposits dating from 18,000 years ago; they were accompanied by remarkably advanced stone tools. The latest finds were from trenches at various depths and thus ages, some as recent as 12,000 years ago, indicating that the cave was occupied for tens of thousands of years.

Another possibility raised by the skeptics is that the discoverers happened to come on a people suffering from microcephaly, a disorder that causes abnormally small brain growth and other deformities.

Recently, British researchers examined the skull of a microcephalic individual at the Royal College of Surgeons of England and found that its braincase appeared to match that of the Flores specimen.

Robert B. Eckhardt, a professor of developmental genetics at Penn State, complained that the new report on the additional jaw failed to support the thesis that these people were a separate species.

"All the paper tells us is that they have identified an early population of small people," Dr. Eckhardt said. "What we are disputing is that people with the brain size of a chimp made these stone tools in the cave. The easiest explanation is that the specimen with the small brain has a small brain because it is abnormal, not a new species."