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3D analysis supports 'Homo floresiensis' as new species

Thursday, July 11, 2013

Media note: U of M anthropology professor and study co-author Kieran McNulty is only available for interviews via phone through Friday, July 12 due to international travel.

Based on the analysis of 3-D landmark data from skull surfaces, scientists from the University of Minnesota, Stony Brook University and the Senckenberg Center for Human Evolution and Palaeoenvironment, provide new, compelling support for the hypothesis that Homo floresiensis was a distinct species of fossil human in an article published today in the journal PLOS ONE.

Ever since the discovery of its remains in Indonesia in 2003, scientists have been debating whether Homo floresiensis represents a distinct species of fossil human, possibly originating from a dwarfed Homo erectus population, or a pathological modern human. The small size of its brain has been argued to result from a number of pathologies, most importantly from a condition known as microcephaly (pathologically small brain).

The study is the most comprehensive to date, simultaneously evaluating two competing hypotheses about the status of Homo floresiensis. The full study is available here:

“[Homo floresiensis] is one of the most exciting fossil discoveries in the last 50 years,” said U of M anthropology professor and co-author of the study Kieran McNulty. “The skull resembles something that died a million years earlier, and other body parts are reminiscent of our three-million-year-old human ancestors, yet they lived until very recently -- contemporaries with modern humans.”

The ancestry of the Homo floresiensis remains is much disputed. Critical questions for scientists include: Did Homo floresiensis represent an extinct hominin species? Could it be a Homo erectus population, whose small stature was caused by island dwarfism? Or did these remains belong to a modern human with a disorder that resulted in an abnormally small brain and skull?

Scientists have proposed possible explanations including microcephaly, Laron Syndrome (a congenital growth disorder) or endemic hypothyroidism, or “cretinism,” (a severe iodine deficiency).

For this most recent study, scientists applied the powerful methods of 3-D geometric morphometrics to compare the shape of the Homo floresiensis cranium (called LB1) to many fossil humans, as well as a large sample of modern human crania suffering from microcephaly and other pathological conditions. Geometric morphometrics methods use 3D models based on anatomical landmarks, computer imaging and statistical analysis to achieve a detailed analysis of shape.

The study found that the LB1 cranium shows greater affinities to extinct fossil humans than it does to pathological modern humans. Although some superficial similarities were found between fossils - LB1 and pathological modern human crania - additional features linked LB1 exclusively with fossil Homo.

“Our findings provide the most comprehensive evidence to date linking the Homo floresiensis skull with extinct fossil human species rather than with pathological modern humans. Our study therefore refutes the hypothesis that this specimen represents a modern human with a pathological condition, such as microcephaly,” stated the authors.

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