Thursday, October 28, 2004

Why were the "Hobbits" of Flores so small?

Just a quick note now on the newly-discovered extinct humanlike species, Homo floresiensis, which I may flesh out further later.

This discovery of tiny human skeletons on the island of Flores in the Indonesian archipelago, dated to 18,000 years old, has cause immense excitement. I was particularly interested in the question of why these people might have been so tiny, only a metre tall.

There have been suggestions that living on a small island, with not much food, could have led these hominids to become very dwarfed. I have two problems with this: one is that Flores is not really a small island, and the other is that, if the people were hunting elephants and so on, shortage of food is not obvious. Ten years ago I published a theory (in the journal Homo, published in Stuttgart in Germany, Vol. 44/3, pp. 284-7) to attempt to explain the short stature of the Pygmies and Negritos of the rainforests of Africa and Asia. Basically, I argued that the dense rainforest canopy reduced the amount of ultraviolet light available to the forest-dwellers; which reduced the capacity for making vitamin D in the skin; which reduced the ability to take up calcium for the skeleton; which made having a small, slow-growing skeleton a good thing. Hence, the small skeleton (and body, of course) of Pygmies and Negritos.

Here is a description of the likely environment of the Flores people:

" We don't know much about the paleoenvironment on Flores yet, but everything's consistent with it being heavily rainforested back in the Pleistocene and probably heavily rainforested until agricultural humans arrived and started clearing the rainforest. "

So, it is possible that the Flores "Hobbits" lived in rainforest, and my theory on why rainforest people become dwarfed could apply to them as well. Perhaps they lived there a very long time, and became correspondingly very small. That is, they evolved very small skeletons to avoid rickets and other bone problems in an environment where there was little ultraviolet light to help make the necessary vitamin D.

Here is a short note I had published on the levels of ultraviolet light in North Queensland rainforest.



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