Professor Maciej Henneberg's claims about the teeth of Homo floresiensis (the Hobbit)
In a popular book he has written with a retired journalist (Henneberg and Schofield 2008, chapter 4), and in claims that he has recently made to journalists at scientific meetings, Professor Maciej Henneberg (Department of Anatomy, University of Adelaide) has stated that the type specimen of Homo floresiensis may have evidence of modern dental work in the left first mandibular molar. He has used this claim in an attempt to cast dispersion on the peer reviewed research conducted at Liang Bua, undermine the status of H. floresiensis, and promote his own poorly informed views (Jacob et al. 2006). When discovered there was no evidence of dental work in the Pleistocene hominin skeletal materials from Liang Bua (Brown et al. 2004). The teeth of LB1, and to a lesser extent LB6, are heavily worn, with dentine exposed on the chewing (occlusal) surfaces (Morwood et al. 2005), without dental fillings and dental caries (Brown and Maeda 2009). Professor Henneberg is either extremely inexperienced with the way teeth wear in hunter-gatherers and earlier hominins, has taken the advice of someone similarly poorly informed, or did not examine the teeth in adequate detail. If any of these circumstances apply then I would have thought that the prudent approach would be to carefuly verify your claims before talking to the media, or putting your thoughts in a book. The presence, or absence, of a dental filling is easily verifiable. Either one is present, or it is not. If there is not a filling then there are implications for the credibility of Professor Henneberg, particularly in relation to his observations and stated expertise. My personal experience is that I have worked with collections of teeth (hunter-gatherer, Neolithic and more recent humans, a variety of hominins and non-human primates) in Australia, Asia, Europe, UK and North America over the last 30 years. Teeth were an important part of my PhD research (1979-1982) and I have maintained my interest, and increased my experience, in the following years. I cleaned the teeth of LB1 using brushes and soft probes, while wearing magi glasses. Grain-by-grain, it was a delicate and slow process. There was no filling in the crown of the mandibular left first molar, or any other teeth. The mandibular teeth of LB1 were described in detail by Brown and Maeda (2010) and dental restoration, of any type, are not present.
In hunter-gatherer populations, for instance indigenous Australians prior to European contact, there was often minimal premasticatory preparation of foods (cooking), and the abrasive content of food (dust, dirt, grit) may also have been high. As a result teeth wore very quickly, and 6-7 years after a tooth had erupted and reached occlusion it was not unusual for the enamel crown to be worn through on the cusps and underlying dentine exposed (Campbell 1939; Molnar 1971; Molnar and Molnar 1990; Murphy 1959; Richards and Miller 1991; Smith 1984). Dentine is softer than enamel and once exposed, the tooth crowns wear more quickly, with the dentine eventually forming a slightly cupped surface surrounded by a ridge of enamel. As wear starts to approach the pulp canals, odontoblast cells in the pulp may start to deposit secondary dentine, filling in some of the pulp chamber and preventing infection. However, rates and extent of occlusal wear may still exceed this secondary dentine deposition, and the pulp be exposed. Secondary dentine typically has a different appearance to primary dentine, forming a darker circle on the exposed occlusal surface.
In skeletal materials from archaeological sites the enamel and dentine in teeth tend to be a slightly different colour. Dentine is more porous, has a higher organic content, does not reflect light as readily as more crystalline enamel, and may take up mineral and organic materials from the archaeological deposit more readily. Where there is a lot of manganese in the soil dentine, and bone, are usually stained a dark brown, in limestone caves dentine stays a chalky white. In other words, both at original inspection and in photographs, you can distinguish between enamel and dentine. Where the enamel is worn to the thickness of a few microns it is semi-transparent and looks different to exposed dentine and thicker enamel at the margins of the tooth. A further complication with archaeological materials is that the post-depositional environment can adversely effect the preservation of enamel and dentine, most commonly erosion, decalcification, chips, scratches, and colour change. Expertise is required to distinguish the results of taphonomic processes from how the teeth appeared during life. All too easy for the inexperienced, or those with a particular bias, to mistake postdepositional damage for evidence of pathology.
Evidence of the way teeth wear, and the appearance of occlusal surface enamel and dentine, is provided by museum collections of hominin and Palaeolithic human skeletons. The examples provided below come from the collection of the South Australian Museum, a few kilometres from Professor Henneberg's Adelaide office. Most of the larger museums around the planet have collections of similar material, and there is a very large scientific literature on tooth wear in pre-urban humans and early hominins (try Google scholar). For each of the images there is a link to a high resolution (300 dpi) version.
|Mandible of a 6-7 year old, pre-European contact, Australian Aborigine. The first permanent molar has reached occlusion fairly recently and has minimal wear. The deciduous molars, which reach occlusion at around 18 months, have extensive wear. Most of the enamel has been removed from the deciduous molars, and the darker coloured underlying dentine exposed.|
|Mandible of a young adult, pre-European contact, Australian Aborigine. The third permanent molar has reached occlusion fairly recently and has minimal wear (18-20 years). Tooth wear has removed the cusps, and most of the occlusal surface fissures, from the first molar. Patches of darker coloured dentine are now exposed. Dentine is not exposed on the occlusal surface of the second molars.|
|Mandible of an older, pre-European contact, Australian Aborigine. The third permanent molar has reached occlusion has diffuse wear. Tooth wear has removed the cusps, and most of the occlusal surface fissures, from the first and second molars. Patches of darker coloured dentine are now exposed on most teeth. Exposed dentine on adjacent teeth is usually the same colour, but note differences between left and right m1. Many teeth are missing pieces of enamel due to post-excavation damage (common im museum collections due to temp/humidity change and handling).|
|Mandible of an aged adult, pre-European contact, Australian Aborigine. All enamel has been removed from the left M1 and the pulp canals exposed. This resulted in an apical abscess, similar for the right second premolar. Due to this pulp infection the dentine in this "dead tooth" becomes a darker colour. Little enamel remains on the second molars and the dentine is deeply excavated, with secondary dentine exposed on the left m1.|
What about Liang Bua Homo floresiensis?
Professor Henneberg has told the media, for instance http://www.theaustralian.news.com.au/story/0,25197,23561788-30417,00.html and http://www.sciam.com/article.cfm?id=flores-hobbit-root-canal, that he is concerned about discolouration he sees on the occlusal surface of the left mandibular first molar of LB1. He has suggested that this may be a temporary filling inserted into this tooth, when LB1 was alive in the 1930's. In other words he is disputing that LB1 died 18,000 years ago. A temporary filling as an amalgam would be more obvious, and he thinks that a temporary would more closely match the colour of the occlusal surface of the tooth. Professor Henneberg has suggested to journalists that I missed the presence of this filling as my research was too hasty and lacking sufficient care. For the record I have spent more than six weeks with the Liang Bua material in Jakarta, and several years with the records (casts, ct scans, radiographs, photographs, etc) in my laboratory. Professor Henneberg spent only a couple of days with parts of the Liang Bua collection after it had been removed to the late Professor Teuku Jacob's laboratory at Gadja Mada University. According to Professor Henneberg's account, shortly after the dental treatment LB1 subsequently died and a 5.5 m deep hole was dug in the cave to bury her. Ignoring the evidence from the stratified archaeological deposit which demonstrates that a 5.5 m deep grave was not dug into the cave, Professor Henneberg's claims can easily be tested with observations of the tooth in question. High resolution (150 & 300 dpi) copies are linked to the images below, all are copyright Peter Brown.
|The left first mandibular molar of LB1, Homo floresiensis, is heavily worn. Most of the enamel has been removed from the occlusal surface. The remaining enamel forms a ridge on the buccal and lingual margins, and there is a thin platform of remaining enamel in the disto-lingual quadrant.. The softer dentine is somewhat scooped out and has a flat white appearance. There is some adhering sediment on the occlusal surface. Absolutely no evidence of any dental work, temporary filling or anything else. The tooth wear and oral health of LB1 are in all respects typical of older palaeolithic and hunter/gatherer humans, and living apes, and distinct from the mesolithic and more recent human burials in the Holocene layers at Liang Bua. Please examine the linked high resolution image.|
|Cross section through the centre of the left side and right side LB1 teeth (based on CT scan data). Dark patch in the centre of the tooth crowns is the pulp cavity. The left mandibular first molar discussed by Henneberg is the first tooth evident in the lower jaw of the left side. CT scans work on the density of the material being scanned. Denser material (more radio-opaque) comes out as lighter colour. A filling in the crown of a tooth would be obvious, just as it is in a dental x-ray. Dental preparations also require the excavation of a specially shaped cavity to remove caries and hold the filling material in place. Neither a photograph of the chewing (occlusal) surface, or these CT scans, show any evidence of a filling in any of the LB1 teeth..|
|3-D rendering of LB1 CT scan data (1 mm slice intervals), with exposed section through the left molars. The cross section is not through the middle of the first molar, but does display a normal healthy bifurcated pulp cavity in this tooth. Again, absolutely no evidence in support of Professor Henneberg's claimed dental work.|
|X-ray of the LB1 mandible, with the left molar teeth indicated. The greater density of dental restorations, relative to enamel and dentine, makes restorations obvious in x-rays. None of the teeth in LB1 have any evidence of dental restorations and Profesor Henneberg's claims are again demonstrated to be speculative fiction.|
There is absolutely no support for Professor Henneberg's claim of a filling (1930's dental restoration) in the crown, or roots, of the left mandibular first molar of LB1. Dr Alan Thorne, one of Professor Henneberg's supporters has stated to journalists that if Henneberg's claims are correct then there are implications for Homo floresiensis http://www.theaustralian.news.com.au/story/0,25197,23561788-30417,00.html . Of course the reverse should also be true. As the claim is a complete fabrication, without any substance, then there are implications for the credibility of Professor Henneberg and his supporters.
Peter Brown, April 2008
Update, February 2011
Most recently, Jungers and Kaifu (In Press) have examined Henneberg and Schofield's claim for a dental restoration in the crown of the left mandibluar M1 of LB1. They conclude
“Our findings corroborate and extend the primary conclusions reached earlier by Brown (2008) and Brown and Maeda (2009). Photographs, a digital radiograph, and micro CTs scans of the left molars of LB1 all reveal no evidence of a dental filling in the left M1.Occlusal wear and white mineral staining of the exposed dentine were confused by Henneberg and Schofield (2008) for a dental filling, but all teeth of LB1 with exposed dentine exhibit comparable degrees of chalkiness. The pulp cavity and the root canals of the tooth were never breached in life and exhibit no evidence of endodontic treatment.”
Brown P, Sutikna T, Morwood MJ, Soejono RP, Jatmiko, Saptomo EW, Due RA (2004) A new small-bodied hominin from the Late Pleistocene of Flores, Indonesia. Nature 431(7012):1055-106
Brown P, Maeda T. 2009. Liang Bua Homo floresiensis mandibles and mandibular teeth: a contribution to the comparative morphology of a new hominin species. Journal of Human Evolution 57: 571-596.
Campbell TD (1939) Food, food values and food habits of the Australian Aborigines in relation to their dental conditions. Aust J Dent 43:1-15, 45-55, 73-87, 141-156, 178-198
Henneberg, M. Schofield, J. 2008. The Hobbit trap. Wakefield Press, Adelaide.
Jungers, WlL. and Kaifu, Y. In Press. On dental wear, dental work, and oral health in the type specimen (LB1 )of Homo floresiensis. Am. J. Phys. Anthropolo.
Molnar S (1971) Human tooth wear, tooth function and cultural variability. Am J Phys Anthropol 34:175-190
Molnar S, Molnar IM (1990) Dental arch shape and tooth wear variability. Am J Phys Anthropol 82(3):385-396
Morwood MJ, Brown P, Jatmiko, Sutikna T, Saptomo EW, Westaway KE, Due RA, Roberts RG, Maeda T, Wasisto S, Djubiantono T (2005) Further evidence for small-bodied hominins from the Late Pleistocene of Flores, Indonesia. Nature 437(7061):1012-1017
Murphy T (1959) Gradients of dentine exposure in human molar tooth attrition. Am J Phys Anthropol 17:179
Richards LC, Miller SLJ (1991) Relationship Between Age and Dental Attrition in Australian Aboriginals. Am J Phys Anthropol 84:159-164
Smith BH (1984) Patterns of molar wear in hunter-gathers and agriculturalists. American Journal of Physical Anthropology 63:39-56
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