'Hobbit' fossil: dwarf or new species?

The "Hobbit" fossils of a tiny human found in Indonesia aren't those of a new species,a primatologist proposes, but actually someone with a genetic illness that causes dwarfism.

Paleontologists announced the discovery of what appeared to be an adult female less than one metre tall in 2004.

The team considered the skeleton, named LB1, to be a member of a new species derived from Homo erectus.

Prof. Mike Morwood, of the University of New England in Armidale, Australia, proposedthe species designation Homo floresiensis.

But the fossil became known as the "Hobbit" in the press, after the diminutive characters in J.R.R. Tolkien's The Lord of the Rings series.

Primatologist Robert Martin of the Field Museum in Chicago and his colleagues challenge the creature's species designation in a technical comment published in Friday's issue of the journal Science.

"The tiny cranial capacity of LB1, which is smaller than in any other known hominid younger than three million years old, is demonstrably far too small to have been derived from Homo erectus by normal dwarfing," Martin said in a release.

Given the tiny brain size and the sophisticated nature of the stone tools found with the fossil, only modern humans such as Homo sapiens could have crafted them, Martin's team said.

Rather, LB1 appears to be a modern human with microcephaly, a disorder that results in a small brain size. Its brain is only 380 cubic centimetres.

LB1's brain should be compared to that of an adult, not a young microcephalic as done in the original paper, the challengers said.

Authors of the original paper defended their work, saying Martin's calculations were based on dwarf versions of other animals and may not apply to early humans.

Other bones found at the site suggest LB1 belonged to a population of early dwarfs, with a body mass, brain size and short legs similar to those found on other isolated islands, Morwood's teamsaid.