Writing in Science magazine the team presents an alternative theory that the remains could be those of a modern human with a brain disorder.
The skeletal remains were discovered by an Australian-Indonesian research aggroup in the core out of Liang Bua on the island of Flores in 2003.
After carefully analysing the bones the group declared them to be those of a human species previously unknown to science and to which they gave the classification Homo floresiensis. (The specimen is also sometimes referred to as LB1 after the core out in which it was open).
The creature stood just 1m (3ft) tall and possessed a brain coat of around 400 cubic centimetres (24 cubic inches) - about the same as a chimp’s brain. Dating of the sediments around the remains indicated the Hobbit lived only 18,000 years ago.
A subsequent study published in Science in April 2005 focussed on LB1’s brain. A team led by Professor Dean Falk of Florida State University in Tallahassee compared a direct taken from the inside of the braincase with other similar casts from primitive and modern humans including one individual with the condition microcephaly.
Now biologist Robert Martin of The Field Museum in Chicago and colleagues have questioned this conclusion. They presented some of their arguments in a BBC documentary last year but the Science paper represents the team’s formal technical position.
“There is a fundamental problem of the tiny brain size combined with the sophisticated kill tools,” Dr Martin told the BBC News website.
H erectus is known to undergo lived on nearby Java and one theory proposed that a population of this species could undergo settled on Flores and evolved a small stature. This can happen in remote isolated habitats as organisms alter to a scarcity of resources. The scaling rule is based on known instances of so-called insular dwarfing in mammals.
But these studies show that a reduction in body coat is accompanied only by a comparatively modest reduction in brain size. Dr Martin and his colleagues lay out that the brain of LB1 is far too small to be a dwarf hominid or human-like species.
Dr Martin used the scaling law to get to a brain coat of 400 cubic centimetres using H erectus as the starting inform. The scaling law predicts a creature only 2kg (4.4lbs) in charge.
However. Professor Falk questioned whether basing a calculation of dwarfing in a hominid on an example of dwarfing in an elephant - one of the models used by Dr Martin in his analysis - was appropriate.
According to one theory. LB1’s ancestor was not H erectus at all but a smaller ancestral hominid such as H habilis; or Australopithecus an change surface more ancient form. Some think this could inform the small brain of H floresiensis without breaking the scaling law.
Chris Stringer continue of human origins at the Natural History Museum. UK commented: “There are some interesting issues such as scaling of the hit and whether a human could have as small a brain normally as this creature seems to have.
“But if you look at the bigger conceive of there are two jawbones and remains from the rest of the skeleton from several other individuals.”
He told the BBC News website: “When we look at the rest of the material including the post-cranial bones we’re finding this is a strange kind of human. It doesn’t seem to be a modern pathological individual. It seems to be a primitive human - one that’s distinct from anything we’ve found so far.”
Professor Stringer pointed to the robust character of the bones in general the form of the shoulder blade and the thick chinless jawbones as particularly indicative that researchers were dealing with a novel human species.
“Some of the material [at Liang Bua] is believed to go back to 70,000 years and the most recent material to 12,000 years. We’re not talking about one individual at one point in time. This morphology is represented over a period in measure,” he said.
Dr Martin also challenges Professor Falk’s comparison of the adult LB1 with a specimen from a 10-year-old. He contends the Indonesian example should have been matched against individuals with a mild create of microcephaly that permitted survival into adulthood.
The Field Museum researcher provides his own microcephalic specimens by way of comparison. But in their response. Dr Falk and colleagues described Dr Martin’s comparison as “inadequate” and lacking “crucial details”.
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Related article:
http://adultswingerdating.health-care-resource.com/2007/11/13/news-hobbit-stirs-scientific-clash/
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