New research from the Proceedings of the Royal Society B raises the possibility that Homo floresiensis was nothing more than population of Homo sapiens that were endemic cretins. The paper, “Are the small human-like fossils found on Flores human endemic cretins?” comes from academics in Australia who
“show that the fossils display many signs of congenital hypothyroidism, including enlarged pituitary fossa, and that distinctive primitive features of LB1 such as the double rooted lower premolar and the primitive wrist morphology are consistent with the hypothesis. We find that the null hypothesis (that LB1 is not a cretin) is rejected by the pituitary fossa size of LB1, and by multivariate analyses of cranial measures. We show that critical environmental factors were potentially present on Flores, how remains of cretins but not of unaffected individuals could be preserved in caves, and that extant oral traditions may provide a record of cretinism.”
What’s cretinism, though? Cretinism is a medical condition that affects growth and development of the organism because the thyroid gland isn’t working correctly. The thyroid gland is a critical endocrine gland, one that secretes a lot of hormones, like thyroxine (T4) and triiodothyronine (T3) which do their thing in metabolic reactions and bone growth. Thyroxin and triiodothyronine are essentially made up of iodine, and deficiencies in iodine affect thyroxine and triiodothyronine production — ultimately affecting metabolism, bone development, etc. and resulting in a dwarf-like stature with small brains, but relatively,
“less severe mental retardation and motor disability than neurological endemic cretins.”
The authors of this new study suggest that what is now looked at as Homo floresiensis is nothing more than a group of Homo sapiens who lived on an island that was deficient in iodine. They look at the pituitary fossa, also known as the hypophysial fossa, a depression in the sphenoid bone which cups the pituitary gland, from the virtual endocast Dean Falk and crew made in 2005. The actual osteological feature I was taught is called the sella turcica, or the ‘turkish saddle.’ Anyways, LB1’s sella turcica is long compared to the overall size of LB1.
When compared to other populations, as well as microcephalics, Kabwe, and Mrs. Ples, LB1’s sella turcica length matched that of myxoedematous endemic cretins from China. I’m not endocrinologist, so I maybe completely wrong in this understanding, but I think the reason why endemic cretins have large pituitary glands, and thus larger sella turcicas, is because without a fully functioning thyroid gland, the pituitary has to go in overdrive — it grows larger to pump out more hormones to stimulate the weakly active thyroid. Actually, I’ve found a citation, Yamada et al.’s “Volume of sella turcica in normal subjects and in patients with primary hypothyroidism and hyperthyroidism,” where this pathology is observed and associated just as I suspected.
The authors also compared what others touted as distinctive primitive features of the Flores hominin, such as the double rooted lower premolar, to endemic cretins. But how they did it seems really fishy. They didn’t actually have the LB6 mandible, nor did they have CT scans of the premolars. What they did have was ‘captured images’ from X-ray scans of that 2005 BBC show, “The Mystery of the Human Hobbit.” Yes, you heard me right. They had screen shots from a television show, where the X-rays of the teeth flashed on the screen. Now, I know accessibility to fossils is a big problem in paleoanthropology, people just don’t wanna share… and researchers often have to resort to less accurate sources to get the data they need. But screen captures from a TV show seems flawed to me.
The authors make no mention that their screen captures came from HDTV, so I’m assuming they plucked it off of standard analog TV resolution. That’s like 704 pixels × 480 pixels resolution, the equivalent of about 0.3 megapixels! A run of the mill digital camera shoots at 7 megapixels nowadays, and the photo quality is still not that great to do a detailed morphological comparison! Regardless, from a resolution of .3 megapixels, the authors were able to compare and contrast fine details like the buccogingival ridge and measure the diameters of the crown.
To be really honest, I don’t know how they were able to get a scale on their measurements…. surprisingly, they didn’t include their image captures. I checked the supplementary materials and don’t see any screen capture of the X-rays included. So I did some sleuthing of my own. The BBC show they got the screen captures from is online, on Google Video. I’ve linked it above. At 5 minutes and 48 seconds, the X-ray of the premolar flashes for a total of seven seconds. I’ve taken a screen capture of the closest zoom of the premolar, and uploaded it. You can get an idea of what sorta resolution we’re talking about. I’m not too convinced one can extract accurate measurements from this, especially without a scale!
The authors go on to compare a whole slew of post cranial features, such as the humeral torsion and the ‘primitive’ wrist bones — stuff we saw in September of 2007, when “The Primitive Wrist of Homo floresiensis and Its Implications for Hominin Evolution,” came out in Science. The authors conclude that the primitive wrist morphology is also a characteristic of myxoedematous endemic cretins, who in total, have brains about half the size of normal humans, way smaller bodies )the don’t grow much taller than 4 feet), and ancestral teeth and wrists. This again is all because iodine wasn’t present in their diets, so important thyroid hormones that aide in growth and development weren’t made readily.
I’d like to believe this paper, really I do. I’ve always had an inkling that Homo floresiensis was a pathological variant of humans When I look at the photos of myxoedematous endemic cretin crania, which the authors supplied in the supplemental materials, I can see similarities to Homo floresiensis. Though I wonder why the authors resorted to virtual endocasts, screen shots, and previously published measurements to do their study? It could be a case that the fossils weren’t made available to them, which then I don’t really hold the authors accountable for why they went about their study in a creative manner… but with Teuku Jacob dead, I don’t think anyone is holding the fossils from Flores hostage, or are they? Anyone care to comment on that?
One last thing, about endemic cretinism… it is seen in population far away from sources of iodine, such as the Swiss and people around the Alps. Lots of other places show it… but iodine deficiency is rarely found in island dwelling populations. That’s because the ocean and sea has a lot of iodine in it, and any food extracted from the sea… like fish, has lots of iodine in it. It is definately possible Flores hominins fished, though no zooarchaeological remains point to that, and thus had little to no iodine deficiency. Just something to think about.
Obendorf, P.J., Oxnard, C.E., Kefford, B.J. (2008). Are the small human-like fossils found on Flores human endemic cretins?. Proceedings of the Royal Society B: Biological Sciences, -1(-1), -1–1. DOI: 10.1098/rspb.2007.1488