Was Homo floresiensis the tooth fairy?15 Apr 2008
It's enough to drive me crazy. The rumor is that LB 1, the near-complete skeleton that serves as the type specimen of Homo floresiensis, may have evidence of dental work on its lower left first molar. Kate Wong wrote about it on the Scientific American blog, and Maciej Henneberg put some of the story in his new book about the Homo floresiensis saga. This means it's not just a rumor anymore: it's news.
So, does the claim have any merit? That's the part that drives me crazy. So much of this whole thing has been framed like a court of inquiry, with lawyer-like arguments about the published record. That's not how science is supposed to work.
For any other skeleton in the world, this claim would be extraordinarily simple and easy to test -- just look at the specimen, scrape at the supposed filling with a dental pick, and see what it is made of: dentin or dental cement? Or, look at a lateral radiograph.
Unfortunately, requests for access to the specimen to test the hypothesis have been denied. And no decent radiograph has emerged. In Kate Wong's article, Peter Brown has provided a CT image with a section of the left lower dentition. But the section appears insufficient to answer the question -- it has rather poor resolution (typical of medical CT scans), and cuts through the lingual cusps of the lower M1, not the buccal (cheek) cusps which appear to have been most affected by the irregularity.
I saw Maciej's pictures of the specimen and listened carefully to his line of reasoning. To be very clear, my opinion has very little value on this question: I've seen a lot of teeth, but I'm no dental anthropologist. At least one dental anthropologist I spoke to thought that the specimen was a fairly unproblematic broken tooth. Others have said it was consistent with drilling. Everybody I've talked to thinks that ultimately the question can only be settled with radiographs or direct observations.
So, I review the logic mainly to express why I would not dismiss the hypothesis of a filling in that tooth without further evidence. There are three elements:
1. The buccal enamel wall has an unusual, straight-edge discontinuity on the crown, and is raised by ca. 1.5-2 mm above the center of the tooth. The mesial enamel wall is broken away, and a whitish, flat, pitted surface characterizes most of the occlusal face, except for the enamel walls and the disto-lingual corner. This contrasts with the wear pattern on the antimere right lower M1, which has normal dentin exposure at the cusps, and the whitish color contasts with the dentin exposure of the other teeth -- although color may have no value given the uncertainty of photographs and the application of a chemical preservative to the specimen.
2. The lower molars are asymmetrically worn, with much more wear on the lower right teeth than the lower left ones. This would appear consistent with the individual chewing much more heavily on the right side than the left for some time prior to death.
3. The alveoli around many of the molars appear eroded, and a small caries appears on the left upper M1, in the region occluding with the lower left M1. The lower left P4 is absent postmortem, and its alveolus also appears eroded. These observations would all be consistent with spreading periodontal disease resulting from an initial large caries in the lower left M1.
Henneberg relays that his colleague Etty Indriati has looked into government records concerning the dental practices on Flores and other rural parts of Indonesia. According to Maciej, the government recommended a certain dental cement rather than amalgam fillings -- even though the cement does not last forever, it was much cheaper than preparing more permanent fillings and took less time to prepare. This cement does not contain metal like amalgam fillings, and might therefore escape detection in a superficial examination.
The CT image appears to show a normal-looking pulp cavity (or at least one with high contrast with surrounding material) in the lingual part of the tooth. That weighs against the idea of an extensive filling, but more detail in that region would be helpful. What is essential is to get a better assessment of the remains themselves.
I try to approach all of this stuff skeptically. The tooth is unusual, but there are ways that it might break naturally in the observed pattern. A premortem break or periodontal disease might cause asymmetrical wear by themselves. Preservative has been applied to the tooth's surface, making photographs misleading. And several skilled osteologists (including one dentist) examined the remains without noticing anything strange enough to scrape the tooth with a dental pick.
All those things weigh against the hypothesis that this tooth has had dental work. And yet, there is something unusual about it, and this hypothesis should be absolutely trivial to test. The CT scan may be enough, although with its resolution I would guess that a radiograph may be more convincing. A simple look at the specimen would be enough. Or a direct radiocarbon date -- which despite the sampling of collagen for DNA testing, was never performed.
So, I would like to see the radiograph.