Wednesday, August 10, 2011

Latest installment in the "hobbit" saga

LB1 (left) next to a modern human skull
Vannucci and colleagues just published the results of a study comparing a couple of brain measurements between microcephalic modern humans, normal modern humans, Homo erectusAustralopithecus and LB1 (the most complete specimen of the recently named species Homo floresiensis).   They argue that their results support the idea that LB1 is a microcephalic modern human, not a distinct species.  I am no brain expert, but I don't really think this study puts forward a slam-dunk argument.  For example, in the measurement that they focus on (cerebellar protrusion), LB1 doesn't seem to me to fit in very well with either microcephalic or normocephalic modern humans.  It is also interesting that they publish a cluster analysis based on their data which shows LB1 clustering more closely with Australopithecus than with microcephalic moderns.
Vannucci et al. 2011, PNAS.  Figures 6 (left) and 5A (right)
LB1 was shocking when first announced....a tiny hominin with an even tinier brain living on the Indonesian Island of Flores as recently as 18,000 years ago.  If this represents a species distinct from H. erectus and H. sapiens (as I would say a majority of the experts currently believe) then it is extremely interesting.  Prior to the discovery of LB1 in 2003, our understanding was that at 18,000 years ago, H. erectus should have been long since extinct, and the only living hominin species should have been modern humans.  The debate over LB1 has been between two camps: one arguing that the Flores hominins are a pathological population of modern humans (with microcephaly) and the other camp arguing that LB1 represents a non-pathological, distinct species of human ancestor that was previously unknown to science.

Bill Jungers clearly isn't buying it the conclusions of this most recent paper.  Jungers has been an outspoken proponent of the view that LB1 is non-pathological.  He makes his opinion crystal clear near the end the of this news piece in Nature.
"[Vanucci et al.] note a fascinating similarity in the cranial measurements found in Homo floresiensis and Australopithecus but ignored it in favour of making the microcephaly argument," he says. "A weird decision, but hobbit politics as usual. 

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