Friday, July 19, 2013

Homo floresiensis Gains Legitimacy

Science Daily has posted a story detailing new examination of the Liang Bua crania by researchers at SUNY Stonybrook, The University of Tubingen, and the University of Minnesota in which they grant legitimate species status to Homo floresiensis.  They write:
The scientists applied the powerful methods of 3-D geometric morphometrics to compare the shape of the LB1 cranium (the skull minus the lower jaw) 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 coordinates of cranial surface anatomical landmarks, computer imaging, and statistics to achieve a detailed analysis of shape.

This was the most comprehensive study to date to simultaneously evaluate the two competing hypotheses about the status of
Homo floresiensis.

The study found that the LB1 cranium shows greater affinities to the fossil human sample than it does to pathological modern humans. Although some superficial similarities were found between fossil, LB1, and pathological modern human crania, additional features linked LB1exclusively with fossil Homo. The team could therefore refute the hypothesis of pathology.
The link to the PLoS paper is here.This is the conclusion of the paper:
Our analyses corroborate the previously suggested link between LB1 and fossil Homo and support the attribution of this specimen to a distinct taxon, H. floresiensis. Furthermore, the neurocranial shape of H. floresiensis closely resembles that of H. erectus s.l. and particularly specimens of early Eurasian H. erectus, although it is unclear whether this latter affinity is best attributed to a close phylogenetic relationship or to a size-related convergence in shape. These results also counter the hypotheses of pathological conditions as the underlying cause of the LB1 neurocranial phenotype, with the possible exception of posterior deformational plagiocephaly, a condition without significant adverse health effects.
Of course, this doesn't mean that it is not endemic dwarfism, just that it is not built on a modern human base. In this case, it may represent a Homo erectus base. Why it was so marked is still an unanswered question.It is also quite possible that this represents founder effect followed by years of selection for diminutive characteristics.  It definitely represents a peculiar side branch in human evolutionary history but not one that defies explanation. 

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