May 19, 2006

Hobbit Sparks Duel of the Anthropologists

This announcement from the Field Museum is one side of the story:

Scientists scuttle claims that 'Hobbit' fossil from Flores, Indonesia, is a new hominid (excerpt):
New evidence highlights failure to respect good scientific practice

CHICAGO--When scientists found 18,000-year-old bones of a small, humanlike creature on the Indonesian island of Flores in 2003, they concluded that the bones represented a new species in the human family tree that they named Homo floresiensis. Their interpretation was widely accepted by the scientific community and heralded by the popular press around the world. Because of its very short stature, H. floresiensis was soon dubbed the "Hobbit."

Increasingly, however, this controversial conclusion is being questioned. In a Technical Comment to be published in the May 19, 2006, issue of Science magazine, scientists led by Robert D. Martin, PhD, Field Museum Provost and world-class primatologist, say that the bones in question do not represent a new species at all. A far more likely explanation is that the bones belonged to a modern human who suffered from microcephaly, a pathological condition that causes small brain size, often associated with short stature.
More on the controversy from the Washington Post (excerpt):
A research team led by primatologist Robert D. Martin, provost of Chicago's Field Museum, argues that no human ancestor could reach a weight of 64 pounds with a brain size of only 23.2 cubic inches and be able to make sophisticated tools like those found with the Hobbit remains.

The Martin team said the Hobbit must have been a modern human with microcephaly -- a condition, usually genetic, in which the brain fails to grow to normal size. "This brain is too small for any explanation besides pathology," Martin said in a telephone interview.

In a rebuttal to the Martin group, a second team led by Florida State University paleoanthropologist Dean Falk defended their earlier research contending that the Flores skull was nothing like that of a microcephalic, and that the remains most likely represent a previously unknown species.

"We are just finishing a big study on microcephalics that confirms our earlier observations," Falk said in a telephone interview. While microcephalic brains shrink with age, causing the inside of the skull to smooth out, the Flores skull is highly convoluted, reflecting the imprint of a fully expanded, fully functioning brain, she said.
Many scientific controversies about paleoanthropological remains are quickly resolved if new facts emerge, but this is a battle which doesn't seem to be going away any time soon, with both sides sticking to their guns.

BTW, here is a picture of a human microcephalic, and another (bottom).

And, finally the abstracts of the two papers.

Comment on "The Brain of LB1, Homo floresiensis"

R. D. Martin, A. M. MacLarnon, J. L. Phillips, L. Dussubieux, P. R. Williams, and W. B. Dobyns
Science 19 May 2006: 999.

Endocast analysis of the brain Homo floresiensis by Falk et al. (Reports, 8 April 2005, p. 242) implies that the hominid is an insular dwarf derived from H. erectus, but its tiny cranial capacity cannot result from normal dwarfing. Consideration of more appropriate microcephalic syndromes and specimens supports the hypothesis of modern human microcephaly.


Response to Comment on "The Brain of LB1, Homo floresiensis"

Dean Falk, Charles Hildebolt, Kirk Smith, M. J. Morwood, Thomas Sutikna, Jatmiko, E. Wayhu Saptomo, Barry Brunsden, and Fred Prior
Science 19 May 2006: 999.

Martin et al. claim that they have two endocasts from microcephalics that appear similar to that of LB1, Homo floresiensis. However, the line drawings they present as evidence lack details about the transverse sinuses, cerebellum, and cerebral poles. Comparative measurements, actual photographs, and sketches that identify key features are needed to draw meaningful conclusions about Martin et al.'s assertions.


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