PARIS (AFP) — Anthropologists have fired another salvo in a feud about diminutive "hobbit" people whose fossilised remains were found in a cave on a remote Indonesian island four years ago.
Combatting a bid to have the hobbits enshrined as a separate branch of the human family tree, they argue the tiny cave-dwellers were simply Homo sapiens who became stunted and retarded as a result of iodine deficiency in pregnancy.
Dubbed after the wee folk in J.R.R. Tolkien's tale, the hominids -- just a metre (3.25 feet) tall and with a chimp-sized brain -- lived around 18,000 years ago on the island of Flores.
The Australian-Indonesian team which announced the discovery in 2004 honoured the cave-dwellers with the name of "Homo floresiensis," or "Man of Flores," to bolster their claim that the hobbits were a new species of human.
They theorised that the little people may have been descendants of prehistoric hominids, Homo erectus, who reached Flores nearly a million years ago.
Marooned from the rest of the world, the hominids evolved a small stature to cope with the available supplies of food. Stone tools and animal remains showed they were skilled in hunting, toolmaking and butchering.
Indeed, the species was so successful, went the argument, that for many years the hobbits lived side-by-side with the bigger-brained H. sapiens -- an idea that implies the two hominids may have been more than kissing cousins.
The theory has ignited one of the fiercest rows in years in the outwardly placid discipline of anthropology, a dispute fuelled by wrangles over access to the site and the remains themselves.
In the latest foray, Australian scientists writing in the British journal Proceedings of the Royal Society B, say the hobbits are H. sapiens who were born without a functioning thyroid, a condition that doomed them to "dwarf cretinism."
As a result, the hobbits would have been severely restricted in growth and mental and motor skills, although not as badly as individuals with microcephaly -- an abnormally tiny brain -- or other neurological disabilities.
"Dwarf cretinism is the result of severe iodine deficiency in pregnancy, in combination with a number of other environmental factors," explains co-author Peter Obdendorf of RMIT University.
"Dwarf cretins grow not much more than one metre (3.25 feet) and their bones have distinctive characteristics very similar to those of the Flores hobbits.
"Our research suggests these fossils are not a new species, but rather the remains of human hunter-gatherers that suffered from this condition."
The study focuses on a dimple in the skeleton called the pituitary fossa which houses the pituitary gland.
In the hobbit skeletons, this depression is unusually enlarged and is a hallmark of so-called myxoedematous endemic (ME) cretins, whose brain size is roughly half that of normal, says Obdendorf.
Other telltales of ME cretinism are a double-rooted premolar teeth, primitive wristbones and a poorly-developed chin, which the H. floresiensis camp claim as signs that the hominids are separate species, the study says.
Previous assaults on the hobbit hypothesis have said the hominids were dwarf H. sapiens, but this is the first to suggest that the dwarfism resulted from diet rather than inbreeding.
Iodine would have been critically absent in the group's nutrition, and the main source -- fish and seafood -- would have been at least 24 kilometres (15 miles) away, on the coast, the study points out.
"Almost all the people who have looked at these fossils have been coming from an evolutionary perspective," said fellow author Charles Oxnard, a professor at the University of Western Australia. "Our idea is that this was an environmentally-caused problem."
The researchers say there is anecdotal evidence from local folklore to back their claim.
The Nage people of central Flores tell tales of ancestors called "ebu gogo" who lived in caves, were short, roughly-built, hairy, pot-bellied and stupid, who stole food, could not cook and had an imperfect language.
"These characteristics are all consistent with ME cretinism," says the study.
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