The Scientist

New postcranial bones and a second jaw matching that of the Hobbit—the much-ballyhooed 18,000 year-old partial skeleton revealed a year ago—strengthens the case that a population of tiny creatures now known as Homo floresiensis lived on the Indonesian island of Flores long after all other human species except our own had gone extinct.

However, paleoanthropologists not connected with the find, published in this week'sNature, say the new discoveries don't settle questions about how the Hobbits fit into the story of human evolution. They argue it's still not clear whether the tiny-brained specimen discovered in 2003 suffered from a deforming malady such as microcephaly, or why the bones exhibit such an unprecedented and bewildering mix of primate traits.

The discovery team claims the bones recovered from two digging seasons are the remains of 9 individual Hobbits that washed into Liang Bua cave between 95,000 and 12,000 years ago.

But at least one expert proposes a startling possible explanation for the unexpected assemblage of bones, which have characteristics that resemble both hominids and other primates. Jeffrey Schwartz, of the University of Pittsburgh, Pa., told The Scientist that the bones might be a miscellany from different taxa, rather than a single human population. "I'm still not convinced that the archeology and the stratigraphy is as well sorted out as they say," said Schwartz, whose specialty is fossil hominids. Allocating all the bones to the genus Homo and the same species is overstepping the bounds of the data, he argued.

Not surprisingly, Australian members of the discovery team dismiss that suggestion. "Every time a duplicate bone or tooth has been found it has had the same set of distinctive characteristics as the first skeleton. No exceptions," Peter Brown, of the University of New England in Armidale, said in an Email. He noted that the skeleton of last year's type specimen, designated LB1, was still partly articulated when discovered. "The arm articulates with the skeleton, i.e., they are from the same individual and not different taxa of animals." He added that there were no apes or monkeys on Flores at the time the Hobbits were alive.

Ralph Holloway, of Columbia University, not a member of the discovery team, also supports the team's conclusions, noting in an Email that the new finds may help gainsay the notion that there was something wrong with the Hobbits. The two mandibles were dated 3,000 years apart, and show enough similarities to render it unlikely that the population was suffering from microcephaly yet somehow continued breeding for hundreds of generations, he said. Still, Holloway has not ruled out brain pathology of some kind in the specific case of LB1, whose brain was smaller than an average chimp's. He is currently studying a brain endocast he made from the original CT scan data of LB1's skull.

The best evidence for settling the brain question is also unlikely: discovery of another skull, John Hawks of the University of Wisconsin, a persistent critic of Flores finds, told The Scientist. "There's something wrong about LB1. The question is, whether what is wrong with it makes it unrepresentative of its population," he said.

Discovery team members have retreated from their original suggestion that the Hobbits are dwarfed descendants of H. erectus. The latest paper emphasizes the bones' resemblance to Australopithecus, the pre-human hominids who lived in Africa from 1-4 million years ago. For instance, Brown noted that the bones' skeletal proportions, brain size, body size, and some other anatomical features match those seen in Australopithecus afarensis, or "Lucy". "Not similar, but the same," he said.

Hawks agreed that comparison to Australopithecus is not unreasonable. "But if they're Australopithecus, why are they on this island when we've never, ever found any other Australopithecines anywhere else outside of Africa?" he asked. "Not only do we have to get them into Southeast Asia, which would be surprising, but we have to get them on a boat across this water passage."