Research is published supporting the idea that the human-like metre-tall species nicknamed hobbit, belongs to a modern human with a brain disease.
Scientists think the Homo floresiensis specimen was a modern human with the disease microcephaly , a condition where the skull and brain are abnormally small, and was not a new human species.
Dr Robert Martin, from the Field Museum, Chicago, and his team say reconstructions of the brain carried out earlier in the year by other scientists were based on a poor cast of the skull and were compared to a child with microcephaly when they should have been compared to a microcephalic adult. They also believe the sophisticated stone tools found with the fossil skeletons were too advanced and had to have been made by modern humans.
Other scientists believe Homo floresiensis may be a dwarf descendant of the earlier human species Homo erectus . It is well known that over time, some animals that are cut off by living on an island can become much smaller, or dwarf versions, of the species they derived from. This is usually due to island animals having a limited food supply and less predators - a smaller body uses less resources and the protection offered by larger size is less important.
The team studied dwarf effects in mammals and found that brain size hardly changes within a species. For example, the difference in the brain size of the smallest modern human, the 1.4-metre Bamuti people of the Congo, and the tallest 2-metre Masai people of east Africa, is extremely small. They say Homo floresiensis's brain is too small to be that of a dwarf Homo erectus .
Other scientists say that Martin's team did not take into account the other bones found at the site, such as limb bones and jawbones, and that they did not go into enough detail in their research.
Chris Stringer , human origins expert at the Natural History Museum, agrees with the first point: 'Other material excavated from the Liang Bua Cave suggests a creature that was fundamentally different from Homo sapiens. In particular the shape and robusticity of the jawbones are something never seen in recent pathologies.'
'However, I agree with the caution about associating all the archaeological evidence from the cave with Homo floresiensis .'
'Modern humans must also have been on Flores during the last 50,000 years, at least, and we don't yet know which behavioural evidence derives from which species.'
The research is published in the journal Science.