Saturday, March 7, 2009

Karen Baab and Kieran McNulty: Modern Procrustes

I found this while searching for news articles on "The Hobbits" or "Homo floresiensis". Sometimes taxonomy gives me headaches. I don't know why humans are so obsessive compulsive about putting things in categories. I guess that same reason is why I put labels on my blog posts.

Anthropologists Karen Baab from Stony Brook University Medical Center and Kieran McNulty from University of Minnesota published "Size, shape, and asymmetry in fossil hominins: The status of the LB1 cranium based on 3D morphometric analyses" in the Journal of Human Evolution last July. Click for .pdf version of the article.

Photo from the Science Museum

Using principal components analysis in shape space and in Procrustes form space, they shrank skulls of modern humans, fossil hominins and apes proportionate to their body so that they can use these new simulated models to compare LB1's skull. They found that LB1's skull closely resembles those of the genus Homo, too different to be those of modern human but close enough to be related to Homo erectus or something more primitive.

"You can't just make things bigger or smaller," McNulty explains. "When things change size, they need different mechanical properties." Or, there could be certain spatial requirements for the brain. A host of factors determine the proportions of the "shrunken" skull.

They concluded from their study that LB1 was more primitive than those of the Asian Homo erectus and perhaps LB1 (Homo florensiensis) was a descendent of a hominin population that predates Asian Homo erectus which underwent a process of size reduction.

Read the press releases from University of Minnesota and Stony Brook University.

I think a lot of people see LB1 as modern human because the skull looks like a shrunken modern human skull. They try to explain why LB1 is so small in stature, from microcephaly to dwarfism. But sometimes looks can be deceptive. LB1 might look like a modern human but it's not. I think that Homo floresiensis is a species of its own and it seems that more and more evidence is surfacing to prove so.


zacharoo said...

I wrote about this paper a while ago, but I don't mind returning to it. The whole Flores thing was fascinating at first, but all the drama that's gone on between researchers is quite disheartening.

I find myself torn between the two camps--pathology and new species. On the one hand, those saying LB 1 is a pathological specimen say you need to disprove the hypothesis of some disease condition before resorting to taxonomy. But there are hundreds of diseases that cause microcephaly, many of which also cause small body-size. Really 'pathology' is becoming an almost untestable hypothesis.

But on the other hand I'm reticent about erecting new species. When you get to something so recent as the Flores material (as young as 12 ka) I have trouble buying into this last refuge of mythical island people (admittedly, the Ngandong 'erectines' persisted pretty long in Indonesia). How long does a population need to be isolated before it's truly a separate species? The whole thing raises several questions, and as David Wake said in a presentation about ring species here at U Mich a few days ago, "It's easy to taxonomize interesting questions out of existence." I wonder if there could be a *cultural* reason for the presence of small-bodied persons on Flores?

So in sum, I'm steering clear of either side. Although I have to say, cranial shape affinities with earlier Homo are pretty convincing.

Raymond Ho said...

If there is one thing that I can take from academia it's researchers bickering around and obsessively arguing over certain things hehe.

I like your idea, and I've also wondered whether there is a cultural reason to LB1 and the other hobbits. Though, I feel that the fossils found inside Liang Bua cave is too small of a sample to test that hypothesis.

Maybe LB1 and her family were the last surviving population of Homo florensiensis when the first modern Homo sapien arrived in Flores? Some might have caught a glimpse of the hobbits and associated them as the mythological "Ebu Gogo"?

Marcel F. Williams said...

The australopithecine-sized brain and australopithecine-like postcranial anatomy combined with the small dentition may suggest that creature is more closely related to Ardipithecus and Sahelanthropus.

This could suggest that the ancestors of the Flores hominin radiated out of Africa at the beginning of the Pliocene (5.3 mya) during a warm period. Crossing the Wallace Line from South East Asia into Flores, however, may have resulted from a series of rafting migration island hopping events during a massive tropical storms.

It would be interesting to find out if the Hobbits originally reached Flores before global sea levels fell 2.6 million years ago or after.

Marcel F. Williams

Raymond Ho said...

*Nod* That's an interesting theory Marcel!