Homo floresiensis Update: Not a Hobbit?

"LB1 is not a normal member of a new species, but an abnormal member of our own," or so concludes Dr. Robert B. Eckhardt, professor of developmental genetics and evolutionary morphology, department of kinesiology, Penn State.

I’ve previously posted about Homo floresiensis (a.k.a. the Hobbit):
New Species or Modern Human? and
Stone Tools of a New Hominid Species?.

Afarensis has also made several posts:
Homo floresiensis: More on Microcephaly
Stone Tools and Homo floresiensis
Tis a Puzzlement: More on Homo floresiensis
The Loom on the Hobbit

And Carl Zimmer’s post, Hobbit as a Monkey? is well worth the read if you are following this topic.

The Eckhardt quote above can be found at this recent Eureka Alert , however.

A research team headed by Teuku Jacob (laboratory of bioanthropology and paleoanthropology, Gadjah Mada University, Indonesia), which included Eckhardt and others, was granted permission to analyze LB1, the nearly complete remains of the individual they now say is mislabeled H. floresiensis. They also had access to the remains of other individuals found at the same site.

The team has published a research article that can be viewed at the Proceedings of the National Academy of Sciences, " Pygmoid Australomelanesian Homo sapiens skeletal remains from Liang Bua, Flores: Population affinities and pathological abnormalities. "

In the article, Jacob et al summarize the evidence against a new species as the following:

  1. Demography, Continuity, and Isolation. The contention that a new species, H. floresiensis, evolved in extended isolation, which would require that migration to the island could only have occurred once and in large enough numbers to have provided sufficient genetic diversity to allow a sustained population of a new species in a very short period of time. The evidence of stegadon migration would indicate that humans couldn’t have been restricted to a single migration. Basically, there wasn’t enough resources to support a population large enough to provide enough genetic diversity for the alleged founder group and yet keep them in isolation long enough (tens of thousands of generations).
  2. Neurocranium and Face. None of the features and characters of the LB1 cranium or the two available mandibles are "outside the range for modern humans of the region." Microcephaly provides the explanation for the small cranium and is indicated by the closure of cranial sutures. In addition 10 other examples of microcephalic skeletons are referred to, noting that none their abnormalities are used to establish new species.
  3. Dentition. Premolar crown rotation and other dental characteristics are consistent with modern pygmies in the Liang Bua region.
  4. Postcrania. Abnormality is evident throughout the postcranial skeleton, particularly with the leg bones. CT scans of leg bone cross sections reveals that the cortical bone is thin (~2 mm), abnormal for any primate over 1 meter tall. This and other features indicate that LB1 is anything but robust, as previously described by others. Deltoid tuberosity of the humerous is nearly absent and the difference in width between the subdeltoid and supradeltoid is small, indicative of weak muscle development.

I must say, Jacob et al present a good case for arguing that others were premature in attempting to establish a new species.

And the article is free via open access!

Jacob, T; Indriati, E; Soejono, R.P.; et al (2006). Pygmoid Australomelanesian Homo sapiens skeletal remains from Liang Bua, Flores: Population affinities and pathological abnormalities. Proceedings of the National Academy of Sciences, 103 (36), 13421-13426.