Homo floresiensis

Paleoanthropology is among the most quarrelsome of fields, so it is no surprise that researchers have gone to war over the remarkable bones discovered in a Liang Bua cave on the Indonesian island of Flores in 2003.

Feb 28, 2005
Tabitha Powledge(tpowledge@the-scientist.com)
<p>THE HOBBIT IN HIDING</p>

Courtesy of Peter Brown

In classifying the specimen LB1 (above), found on the island of Flores in Indonesia, Australian and Indonesian scientists noted its short stature (1 meter) and small cranial capacity, measured at 380 cm3. While they contend it represents a new species, others claim it is a Homo sapiens with microcephaly. Further testing may sort its origins if more researchers can gain access to the sample. A modern human skull is shown at right for comparison.

Paleoanthropology is among the most quarrelsome of fields, so it is no surprise that researchers have gone to war over the remarkable bones discovered in a Liang Bua cave on the Indonesian island of Flores in 2003. But the battle over the Flores find (nicknamed 'The Hobbit' because the type specimen, LB1, is just one meter tall12) has an extra element, bizarre even for human paleontology. An influential scientist not connected with the find has carted the bones off from the National Research Center for Archaeology in Jakarta to his own institution, raising fears that researchers, especially the Indonesian and Australian teams that found the artifacts, will no longer be able to study them.

Without access to the bones, researchers have little hope of substantiating the most astonishing claims: that the remains are of a species called Homo floresiensis, tiny descendants of Homo erectus who possessed a material culture similar to humanity's early days – despite having a brain smaller than an average chimp's – and coexisted with Homo sapienson Flores as recently as 12,000 years ago. Teuku Jacob, professor emeritus of paleoanthropology at Gajah Mada University in Java and the person who took the bones, says the claim is nonsense. He asserts that the bones belong to a microcephalic H. sapiens. DNA studies could settle the question, but the Oxford geneticist originally recruited to examine the specimens' DNA says his studies are on hold until he can get access to the bones.

CARTED AWAY

Chris Stringer, who heads the human paleontology department at the Natural History Museum in London, says, "From comments I have received or heard, most scientists are very concerned about what has happened to the material ... What has happened threatens all further research on the Flores site."

Jacob says that the archaeological center's skeletal finds have been referred to his lab for more than 40 years. "In July 2004 the center persuaded us to pack and transport them [the bones] carefully to our lab," he says. One reason was fear that the bones would be spirited abroad and become difficult to recover. As for access, Jacob declares that scientists around the world have done research in the paleontology collections at Gajah Mada, which are particularly rich in H. erectus fossils. Robert Eckhardt of Pennsylvania State University recounts that Jacob has twice invited him to come study the Flores find.

Indonesian researchers discovered the bones, and Australian scientists did many of the analyses. Michael Morwood of the University of New England in Australia writes in an E-mail: "The excavation team has no plans to ask Prof Jacob for access to our finds." Morwood reports that Jacob promised to return the bones on Jan. 1, 2005, a deadline that Tony Djubiantono, director of the Indonesian Center for Archaeology, has extended more than once.

It's a turf war with scientific battles. The authors argue that LB1 is a miniature descendant of H. erectus. "Probably not," says Jeffrey Schwartz, of the University of Pittsburgh, who has intensively studied fossils attributed to H. erectus. LB1 is "like a Rube Goldberg version of hominids," he declares. "When I look at its features I just don't know what to do with it." Schwartz says the knee is apelike, the pelvic region is hominid-like, but not like sapiens, and the teeth are unlike any in the fossil record attributed either to hominids or apes. "The only thing that looks H. sapiens about this to me is the thinness of the cheekbones below the eye and the concavity of that region below the eye." He's not even sure about LB1's gender. The researchers had concluded that LB1 is female, but Schwartz says the pelvis strikes him as intermediate between male and female.

"I am open to any interpretation until the research is complete," says Etty Indriati, of Jacob's lab, who is studying the Flores remains. She thinks LB1's skull is more modern than archaic, and the incisor and canine teeth and molars are sapiens-like, too. A lower premolar is peculiar, but wide variation is common in those teeth. Brain size, which she measured at 430 cm3, is smaller than any known for erectus or sapiens, and hence she is leaning to the microcephalic hypothesis.

BRAINCASE BATTLES

If LB1 is an example of microcephaly in the Homo genus, it's like none ever reported before. Geoffrey Woods, neurogeneticist at the University of Leeds, UK, says the head seems in proportion to the body, and surviving for three decades suggests that LB1 probably was not mentally deficient. That makes LB1 quite unlike the people he studies, who have primary microcephaly, or people with similar disorders. Woods notes, however, that "it is impossible to be sure."

William Dobyns, neurogeneticist at the University of Chicago, says the researchers dismissed microcephaly too quickly as an explanation for LB1's chimp-like cranial capacity. He suggests that it's similar to microcephalic osteodysplastic primordial dwarfism type II (MOPD II). The usual MOPD II skeletal abnormalities are not all present, Dobyns acknowledges, but the head is so extremely small that it's reasonable to diagnose a midget microcephalic H. sapiens – if not MOPD II, then some other syndrome that has yet to be described.

"There is no way this could be MOPD II," says Judith Hall, medical geneticist at the University of British Columbia in Vancouver, who has studied the autosomal recessive condition thoroughly. She points out that the skull bones are not thin enough for MOPD II. Moreover, few people with MOPD II survive for long, and there are no known cases of reproduction among them.

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Courtesy of Peter Brown

Hall says LB1 strikes her as similar to known groups of isolated Central Americans who are tiny as a result of poor nutrition, and whose small size can persist for generations even when their diet improves. Indonesia is also home to groups of small people.

Publication of other finds made last year at the Flores site may or may not help. "With the remains of at least six H. floresiensis individuals represented between 74 and 12 kyr, it is very clear that we are not dealing with a pathological [microcephalic] dwarf as has been claimed," Morwood notes. But Maciej Henneberg, paleoanthropologist at the University of Adelaide in Australia, points out that these individuals are represented by small bone fragments, and one by a single tooth. "Neither of those other individuals has a braincase preserved to show its small size, while some long bones, though small in comparison with an average modern person, are well within the range observed in H. sapiens."

Perhaps details of the brain will clarify classification. These details can be imprinted inside the braincase, and researchers can reproduce them on endocranial casts. Peter Brown, of the University of New England, made a brain endocast last year. "In this case, the question will be whether the morphology of the cerebral cortex (as reflected on the endocast) appears apelike or more like a miniature version of a human brain. Brain size in living primates, including humans, does have a small, but significant, correlation with cognitive abilities. But a more important factor is the organization, wiring, and neurochemistry of the brain in question, regardless of its size," Dean Falk explains. Falk, a paleoanthropologist at Florida State University in Tallahassee, is collaborating with Morwood and Brown on endocast studies and reports that a paper on the topic is under review.

RECOVERING DNA

DNA studies won't explain everything, but mitochondrial DNA could at least reveal whether H. floresiensis is actually a tiny H. sapiens. Mitochondrial (mt)DNA recovered from Neandertal fossils is quite different from H. sapiens mtDNA, and researchers have argued that it demonstrates Neandertals were not part of the human lineage. Alan Cooper, the ancient DNA specialist at Oxford who is carrying out the discovery team's studies, says that H. erectus mtDNA should also look very different compared to H. sapiens mtDNA.

DNA recovery is a long shot. The hot, wet conditions at Liang Bua are the worst possible for preserving it, and moving the specimens from place to place increases chances of contaminating it with extraneous sequences. At press time, Jacob reportedly had permitted Svante Pääbo's lab at the Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany, to attempt DNA studies on the Flores bones.

Cooper says he is hopeful that his own research can proceed, too. Early soil results, he says, are encouraging. "Mostly I think we got DNA from plants in the sediments. But it's kind of good because at least it means potentially DNA is capable of surviving at the site."

Cooper had hoped to get permission to drill into a Liang Bua hominid tooth (a successful strategy in other ancient species) in search of DNA that has been protected from the elements. But now he says, "Because of all the complications with the actual material, we haven't gotten any further on that. I'm still optimistic we will in the long term, but there's a good bit of politics to be sorted out there."