When researchers found 18,000-year-old bones of a small, humanlike creature on an Indonesian island in 2003, they concluded that the bones represented a new species in the human family tree.

This view was widely accepted among scientists and trumpeted by the press. Because of its size, the creature was nicknamed the “Hobbit.”

But a growing number of scientists have raised questions about the claim.

In a new paper, some researchers say the bones are probably just from an ordinary person who suffered microcephaly, or small-headedness. Microcephaly is often associated with short stature also.


Skull cast and cast of the brain case of a modern adult with microcephaly. Scientists are using the specimen, from the Royal College of Surgeons in London, to argue that the "Flores Man" skull could also have been a microcephalic adult. (Photo by John Weinstein, Courtesy of The Field Museum)

“There has been too much media hype and too little critical scientific evaluation,” said primatologist Robert D. Martin, provost of the Field Museum of Chicago and the paper’s lead author.

He blasted some of the research that went into the case as “unacceptable” in quality.

But supporters of the initial finding gave no ground. They argued that Martin’s own study of the evidence lacks detail and focus.

The proposed new hominid species was given the scientific name Homo floresiensis, or informally Flores Man, because the bones were found on Flores Island. Its interpretation as a new species was based on a specimen labeled LB1, consisting of a little adult skull and partial skeleton about three feet (91 cm) tall.

It was initially described as a “dwarf” species related to Homo erectus, a human ancestor that lived as long as 1.8 million years ago. The account was appealing because islands are known to play tricks on the evolution of animals, sometimes making them shrink due to shortages of food and lack of predators.

But all mammals that have shrunk for those reasons, or any others, have done so within certain parameters, Martin and colleagues argued in their paper, in the May 19 issue of the research journal Science. Body size can shrink considerably, but brain size always shrinks moderately.

LB1’s 400-cubic centimeter brain is too small to follow this law, they argued. For it to be a “dwarfed” form of H. erectus, they added, it would have had to be just one foot (30 cm) tall and weigh only four pounds (less than 2 kg) to explain such a small brain.

Also, they wrote, sophisticated stone tools found near the bones contradict the tiny brain size. Based on the tools’ workmanship, “there is no way they were made by anyone other than Homo sapiens,” our species, said the Field Museum’s James Phillips, an anthropologist and member of Martin’s group.

Supporters of the new-species theory have considered and rejected the microcephaly interpretation before, based on a study of what they said is a copy of a known microcephalic skull. Their analysis found it was clearly different from the Flores Man specimens.

But Martin countered that the “skull” used in that study was a poor comparison piece because it came from a 10-year-old and is a defective plaster copy made of two mismatched parts.

This copy “is inappropriate for any scientific study,” Martin said. “It was the worst possible choice… [it] is one of the smallest that I have so far found in a survey of over 100 human microcephalics.” Moreover, his team argued, the study had involved just that one skull, whereas microcephaly takes dozens of forms.

Defenders of the original findings shot back in a response published in the same issue of the journal.

First, they wrote, they weren’t claiming—as Martin’s group implied—that the fossil represented a straightforward miniaturization of H. erectus.

The initial report on the fossils did suggest something to that effect. But the later study with the microcephalic skull cast raised some doubts about this. Its authors suggested the alternate possibility that both species descended from a common ancestor.

The fact that researchers studied a 10-year-old’s skull is unsurprising, as most microcephalics die young, wrote the authors of the response, Dean Falk of Florida State University in Tallahassee, Fla., and colleagues. The authors include scientists involved in both the original, 2004 report proposing a new species, and in the later microcephalic skull study.

A competing analysis of microcephalic skulls from Martin’s team is flawed, the group added. “The line drawings they present as evidence lack details about the transverse sinuses, cerebellum, and cerebral poles,” important structures, they wrote.

“Comparative measurements, actual photographs, and sketches that identify key features are needed to draw meaningful conclusions,” they added. Without this evidence, Martin’s claims “remain unsubstantiated and difficult to address in further detail.”

ABOUT THE AUTHOR

Science writer Jack Lucentini is founder and editor of the World Science science news webzine. He has worked as a staff writer at three daily newspapers, and as a freelance science writer for a range of publications including The Washington Post, Discover magazine and The Scientist magazine. He earned his bachelor's degree at Oberlin College in Oberlin, Ohio in 1993.