Washington, April 28 : Scientists at Florida State University in Tallahassee say that remains of Homo floresiensis, also known as hobbits, do not show any sign of growth disorders, refuting earlier claims that hobbits were pygmy Homo sapiens that suffered from a growth disorder.
Lead researcher Dean Falk and her Florida State colleague Angela Schauber came to this conclusion after studying computer-generated reconstructions of the fossilized skulls of the small islanders.
They suspect that H. floresiensis-especially as represented by a partial skeleton called LB1-adapted to a challenging island environment by evolving into a smaller but proportionally equivalent version of an ancestral species, possibly Homo erectus.
"LB1 didn't have any of the growth pathologies that have been attributed to it," Falk said.
A study unveiled last year suggested that LB1 exhibits 33 skeletal symptoms of Laron Syndrome, a type of insensitivity to growth hormones.
Besides a reduction of face and limb size, this condition includes a round protrusion of the forehead and a depressed ridge on top of the nose.
Falk, however, says that measurements, photos, and 3-D computer tomography reconstreuctions of LB1 do not show any similarity to published data on the anatomy of Laron Syndrome.
She says that LB1 displays unique skull and tooth traits. She says that it also possesses "whopping long feet" relative to body size, in contrast to the typically small feet observed in Laron Syndrome.
Apart from this, preliminary findings also show that LB1 did not suffer from one form of microcephaly, a genetic growth disorder, or from cretinism, a nutritionally influenced growth disorder.
Schauber used museum skeletal collections to establish that certain species of foxes and mice have evolved into "proportional miniatures" of larger counterparts.
"The same process could apply to H. floresiensis," she says.
She says that island gray foxes, found on islands off the California coast, show the same brain size relative to body size as larger mainland foxes do.
The research also showed that dwarf little mice matched the relative brain size of much larger, normal-sized mice, she adds.
Schauber says that LB1 shows no signs of having had a relative brain size distorted by any growth disorder, and could well have been a proportional dwarf, as observed in foxes and mice.
Robert Eckhardt of Pennsylvania State University in University Park, however, still regards LB1 as a pygmy Homo sapiens that suffered from a still-undetermined growth disorder.
About 400 dwarfing syndromes exist in people today, leaving an extensive list for Falk and her fellow hobbit advocates to consider for LB1, Eckhardt said at the annual meeting of the American Association of Physical Anthropologists, where Falk and Schauber presented separate papers.
Primitive-looking features of LB1's wrist and arms actually fall within the range of variation for people today, Eckhardt argued.
"H. floresiensis is an imaginative composite," he concluded.