Homo floresiensis: The Debate Continues

A new article on Homo floresiensis has been published in PNAS (and is fortunately open access). The lead author of the piece is Teuku Jacob and is quite interesting. Carl Feagan and John Hawks both have some interesting things to say about it. The New York Times also has a story on it (including some comments from Peter Brown).

Since Hawks and Feagans have provided excellent summaries I will confine myself to some random thoughts.
Hawks finds the asymmetry argument convincing and dismisses Browns’ response (distortion due to post depositional processes):

Yes, it is true that any archaeological specimen is likely to be distorted to some extent by reconstruction or postdepositional deformation. That might be true of this skull also. But in this case, the asymmetry clearly extends to morphological characters that should be relatively unaffected by such distortion. For example, the position of the mental foramen shouldn’t change by 40 percent from being buried in wet ground. And while distortion might affect the curvature or flatness of the occiput, it shouldn’t affect the relative development of the nuchal torus or mastoid regions on each side, which must be a consequence of different muscle development or configuration.

I think I’m going to keep an open mind on that one – though I must admit I am somewhat skeptical that it is not due to post depositional processes.
To me the most interesting point concerns muscle weakness. Although the Liang Bua postcranial remains are quite robust they have weak muscle markings and thin cortical bone (and lets not forget the humeral torsion which is odd – and attributted to extremely weak muscle development by Jacob et al).
Comment from the paper that caused me to say ouch:

The holotype statement (1) describes and illustrates a ”right”complete femur, but this bone is a left femur.

Like Hawks, I find the island biogeography arguments less than convincing (think Pitcairn Island) and for much the same reasons.
Which brings me to one of the more interesting, if minor, aspects of the paper. According to most of the books and papers on paleoanthropology that I have read the mental eminence, or chin, is a pretty diagnostic trait for Homo sapiens. Apparently, though, some of the Flores islanders have no chins (I’ll discuss this in my next post).
Overall, I think this will be more of a problem, but we will keep arguing over it til more skulls are found. The problem is that we only have one data point (LB1) and until we have more skulls the argument is going to continue. Unfortunately, further excavations at Liang Bua are forbidden…

2 Responses

  1. Carl Feagan and John Hawks both have some interesting things to say about it.

    Though its fair to say that Hawks had far more to say about it than I. As usual, he’s a wealth of information and opinion, as is your earlier post about the humeral torsion

  2. I too found the asymmetry telling. That said, keep in mind we have but the single skull from the site. If LB1 came from a site that has produced other, human skulls, then the prohuman arguments would hold more weight for me. As it is, LB1 could to be an abnormal specimen of H. floresiensis. Even the recreation of how her skull might have looked if the larger side been her normal condition doesn’t look all that modern human to me. Might be within normal human range, but by any measure she would’ve been an outlier on the charts.
    And what about her lower jaw? As I understand it, even those modern humans who totally lack a chin still have the modern human lower jaw. A light weight structure, even in characters like the young George Washington, when compared to the heavy jaw bone of an animal such as H. Erectus or H. Heidelbergeinsis. When I see a picture of LB1’s skull I see a heavy jaw. One shaped more like the jaw of an H. erectus.
    Finally. What about the other post-cranial skeletal remains? While we have just the one skull, don’t we have post-cranial remains from other individuals? Have they been studied? Not to the same degree as LB1’s skull, at all? What are we reading from those bones? What do they say?
    Have we become fixated on one line of evidence to the detriment of scientific inquiry?

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