A paper published today is set to re-ignite debate over the origins of so-called Homo floresiensis - the ‘hobbit' that some scientists have claimed as a new species of human.
The University of Western Australia's Emeritus Professor Charles Oxnard and his colleagues, in a paper in PLoS ONE have reconfirmed, on the post-cranial skeleton, their original finding on the skull that Homo floresiensis in fact bears the hallmarks of humans - Homo sapiens - affected by hypothyroid cretinism.
The remains, allegedly as recent as 15,000 years, were discovered in 2003 in the Liang Bua caves on the Indonesian island of Flores by archaeologists seeking evidence of the first human migration from Asia to Australia.
When Professor Oxnard and fellow Australian researchers suggested in a 2008 paper that the skull showed evidence of endemic dwarf cretinism resulting from congenital hypothyroidism and were not a new species of human, their claim caused controversy.
In order to test their thesis, in their new paper Professor Oxnard and his team summarised data on the rest of the skeleton and mathematically compared the bones of cretins in relation to chimpanzees, unaffected humans and H. floresiensis. They used two methods with different statistical bases: principal components analyses (PCA) and non-metric multi-dimensional scaling (MDS).
Their work confirms the close grouping of H. floresiensis with the hypothyroid cretins, and the clear separation from both modern humans and from chimpanzees. This leads them to conclude that the Liang Bua remains were indeed most likely cretins from a population of unaffected H. sapiens. They have, further, provided a series of predictions for the further testing of the cretin hypothesis.
"This is consistent with recent hypothyroid endemic cretinism throughout Indonesia, including the nearby island of Bali," Professor Oxnard said.
"Cretinism is caused by various environmental factors including iodine deficiency - a deficiency which would have been present on Flores at the period to which the dwarfed Flores fossils are dated."
Professor Oxnard has received the Charles R. Darwin Award for Lifetime Achievement in Physical Anthropology; was honoured as the dedicatee on a book Shaping Primate Evolution, Cambridge University Press; and was awarded the Chancellor's Medal of The University of Western Australia.
His co-authors in his most recent paper are Professor Peter Obendorf, School of Applied Sciences, RMIT University, Melbourne; and Professor Ben Kefford, Centre for Environmental Sustainability, Department of Environmental Sciences, University of Technology Sydney.
PLoS (Public Library of Science) ONE is an international, peer-reviewed open-access online publication.
Emeritus Professor Charles Oxnard (UWA School of Anatomy (+61 8) 9284 6282
and Human Biology and Forensic Anthropology Group)
Janine MacDonald (UWA Public Affairs) (+61 8) 6488 5563 / (+61 4) 32 637 716