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Dental wear patterns in early modern humans from Skhul and Qafzeh: A response to Sarig and Tillier
Accepted Manuscript Title: Dental wear patterns in early modern humans from Skhul and Qafzeh: A response to Sarig and Tillier Author: Luca Fiorenza Ottmar Kullmer PII: DOI: Reference:
S0018-442X(15)00043-8 http://dx.doi.org/doi:10.1016/j.jchb.2015.04.002 JCHB 25393
To appear in: Received date: Accepted date:
17-11-2014 14-4-2015
Please cite this article as: Fiorenza, L., Kullmer, O.,Dental wear patterns in early modern humans from Skhul and Qafzeh: A response to Sarig and Tillier, Journal of Comparative Human Biology (2015), http://dx.doi.org/10.1016/j.jchb.2015.04.002 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Dental wear patterns in early modern humans from Skhul and Qafzeh: A response to Sarig and Tillier Luca Fiorenzaa,b*, Ottmar Kullmerc a
ip t
Earth Sciences, University of New England, Armidale NSW 2351, Australia Department of Anatomy and Developmental Biology, Monash University, Melbourne VIC 3800, Australia c Senckenberg Research Institute, Senckenberganlage 25, 60325 Frankfurt am Main, Germany
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b
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Received 17 November 2014; accepted 14 April 2015
Ac ce p
*Corresponding author. Tel.: +61 2 6773 2357, fax: +61 2 6773 3030. Email address: [email protected] (Luka Fiorenza)
Page 1 of 12
ip t
Abstract
cr
The use of teeth as tools for manipulating objects and simple food-processing methods was common among prehistoric and modern hunter-gatherer human populations. Paramasticatory
us
uses of teeth frequently produce enamel chipping and distinctive types of dental wear that can readily be related to specific tool functions. In particular, the presence of unusual occlusal wear
an
areas (named para-facets) on maxillary teeth of prehistoric, historic and modern hunter-gatherers has been associated with cultural habits involving extensive use of teeth (Fiorenza et al., 2011;
M
Fiorenza and Kullmer, 2013). However, Sarig and Tillier (2014) believe that this wear had been caused by pathological occlusal relationships rather than by the use of teeth as tools. In this contribution, we show how occlusal contacts are created and how it is possible to distinguish
d
between masticatory and non-masticatory wear facets by using an innovative digital approach
te
called Occlusal Fingerprint Analysis. Statistical results from the analysis of comparative modern samples clearly demonstrate that described para-facets in Skhul and Qafzeh could not have been
Ac ce p
produced by dental occlusal anomalies such as malocclusions and crossbites. Moreover, dental pathologies in prehistoric humans were extremely rare. Only with the adoption of the modern lifestyle between 18th and 19th centuries, did the emergence of malocclusions become significantly more common. Because more than 50% of the Skhul and Qafzeh individuals analysed in our study is characterised by this distinctive type of wear, it is highly unlikely that their para-facets occurred as a result of dental pathologies.
Introduction In a recent article, Sarig and Tillier (2014) questioned if the analysis of non-masticatory dental wear facets (here called para-facets) can effectively be used to reconstruct the cultural behaviour in extinct human populations. In their contribution they particularly refer to a previous study where para-facets have been recognised in the dentition of early modern humans from Skhul and
Page 2 of 12
Qafzeh (Fiorenza and Kullmer, 2013). According to Sarig and Tillier (2014), these wear areas are not created by non-masticatory habits, such as the use of teeth as tools, but are the product of Angle Class II malocclusion (Qafzeh 9) and crossbite (Qafzeh 11 and 15). In this response, we will address some of the arguments posited by Sarig and Tillier (2014) on
ip t
dynamic occlusion in prehistoric human populations.
cr
Analysis of fragmentary human fossil remains
Sarig and Tillier (2014) argued that the identification of para-facets should not be carried out
us
in the presence of isolated teeth, or in general when the antagonist teeth are absent, because wear facets are created by the contacts between upper and lower teeth, and the creation and appearance
an
of wear facets depend on the antagonistic relationship (e.g., Every, 1972, Kaidonis, 2008, Kullmer et al., 2009). The human fossil record is usually fragmentary and most often constituted of isolated teeth, e.g. as in the case of Neanderthal dental remains from Krapina (Radovčić et al.,
M
1988; Wolpoff, 1978). To overcome this problem and make the interpretation of results more robust, biological anthropologists commonly use modern comparative groups. Similarly, we have
d
initially tested if this unusual type of dental wear facets can be the result of a normal masticatory behaviour by analysing a modern human sample of upper and lower teeth with reproducible
te
occlusal pathways and distinctive antagonistic contacts (Fiorenza et al., 2011). In this study we
Ac ce p
found that almost none of the specimens (94.1%) characterized by this type of wear exhibit complementary wear facets on the lower teeth. Each wear facet identifiable in the upper teeth must leave a matching facet in the opposing lower dental arch (e.g., Every, 1972; Kaidonis, 2008). Statistically significant absence of matching facets in the lower teeth led us to conclude that this unusual type of wear was not created by a normal chewing behaviour (Fiorenza et al., 2011).
Occlusal Fingerprint Analysis (OFA) method To further corroborate our initial explanation we have created a three-dimensional (3D) occlusal compass for each tooth analysed in order to quantitatively describe the major occlusal movements responsible for the creation of wear facets (Kullmer et al., 2009, 2012). Starting from a position of centric occlusion (maximal intercuspation), the dental occlusal concept identifies five major mandibular movements (Douglass and DeVreugd, 1997).
Page 3 of 12
The spatial directions of the para-facets found in some modern human specimens and in the Skhul and Qafzeh groups do not statistically fall within any of the mandibular directions described by the dental occlusal concept. The only reasonable explanation for their formation is a non-occlusal creation, such as the use of teeth as a tool (Fiorenza et al., 2011). Observations of
ip t
Middle Palaeolithic humans from the Levant showed that this unique type of wear in the upper molars was remarkably frequent (52.2%). Absence of complementary contacts in the lower teeth
cr
and the occlusal compass analyses confirmed that these wear areas could not have been created by normal masticatory behaviour but were most likely caused by tooth-tool uses (Fiorenza and
us
Kullmer, 2013). These results are not surprising. There is overwhelming evidence showing how prehistoric and historic human populations used their teeth as tools for tearing, holding and manipulating a variety of objects (Eshed et al., 2006; Frayer and Russell, 1987; Molnar, 1971,
an
1972; Smith, 1984).
Consequently, our results are in disagreement with Sarig and Tillier (2014) when they
M
question if the analytic approach in Fiorenza and Kullmer (2013) study was scientifically valid; while Sarig and Tillier’s (2014) interpretation is only based on qualitative observations of three
d
individuals, our approach is centred on quantitative measurements and statistically robust method, which we used to analyse and compare 35 modern hunter-gatherer individuals and 158
Ac ce p
te
human fossil specimens (Fiorenza et al., 2011; Fiorenza and Kullmer, 2013).
Misinterpretations of results
Another major aspect to consider in the study of Sarig and Tillier (2014) is their misinterpretation of the results and conclusions drawn by Fiorenza and Kullmer (2013). While it is true that in the latter contribution it was hypothesised that the presence of para-facets in Near Eastern Neanderthals and anatomically modern humans could have been interpreted as evidence for cultural interaction, this was only one of the two explanations proposed. We formulated two distinct and exclusive hypotheses: 1) independent cultural habits, and 2) possible cultural interactions. Sarig and Tillier (2014) also mistakenly analysed and discussed the interpretation of the presumed para-facets on first maxillary molars of the specimen Qafzeh 15, where we found parafacets only on the deciduous molars (see Table 1 in Fiorenza and Kullmer, 2013) and not on the M1 (Fig. 1).
Page 4 of 12
To avoid further confusion, we include here a table that contains all the specimens analysed in the previous study (Fiorenza and Kullmer, 2013), clearly showing which maxillary molars displayed para-facets and which not (Table 1).
ip t
Frequency of malocclusions in prehistoric human populations
An increase in malocclusion took place relatively recently, between 18th – 19th centuries with
cr
the adoption of modern lifestyles (e.g. Varrela, 2006). It is believed that the introduction of soft and energy-rich foodstuffs in the daily diet caused a strong reduction of the masticatory forces,
us
decreasing the number of chewing cycles and consequently shortening the duration of mastication (Corruccini, 1984). The decrease in masticatory-functional demands has brought
an
about disequilibrium in the dynamic relationships between occlusion and dentition, causing an increase in occlusal variation characterized by misalignment of teeth (Begg, 1954; Begg and Kiesling, 1977; Corrucini, 1984; Kaifu et al., 2003; Varrela, 2006). Malocclusions, however,
M
were extremely rare in archaic humans (Begg, 1954; Begg and Kesling, 1977; Corruccini and Pacciani, 1989; Hunt, 1961; Kaifu et al., 2003).
d
We do not disregard that Qafzeh 9 is characterized by a crossbite in the left anterior dentition in the position of the left I2. However, the presence of a real posterior crossbite is questionable
te
and cannot be related to the development of para-facets in the upper molars. If we associated the
Ac ce p
presence of presumed para-facets with malocclusion, as interpreted for Qafzeh 9, 11 and 15 by Sarig and Tiller (2014), we would expect that the early modern human populations from Skhul and Qafzeh frequently displayed misalignment of teeth (> 50%), an unmatched result in any known prehistoric human population. It is therefore highly unlikely that the para-facets found in the upper molars are the product of malocclusion, such as edge-to-edge occlusion and crossbite, as suggested by Sarig et al. (2013) and Sarig and Tillier (2014). While these authors showed possible contact between para-facets and lower teeth in Qafzeh 11 and 15 (Figs. 2 and 3; Sarig and Tillier, 2014), they did not illustrate any contact details nor the existence of the complementary wear facets on the occlusal surface of the lower crowns. Moreover, a posterior crossbite commonly occurs when the buccal cusps of the maxillary teeth occlude lingually to the buccal cusps of the corresponding mandibular teeth (Harris and Corruccini, 2008; Nerder et al., 1999). In modern westernised societies posterior crossbite is common in the early stages of development, usually producing a lateral shift on one side of the mandible (or unilateral
Page 5 of 12
crossbite) (Tollaro et al., 2002). The much less common bilateral crossbite usually results in asymmetrical mandibles (Veli et al., 2011). In our early modern human sample we found that three specimens from Qafzeh and two specimens from Skhul show para-facets on both sides of the jaw (Table 1). In this particular
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scenario, if we hypothesised that the attritional facets are caused by malocclusion, we would expect to find the unusual cases of bilateral crossbite. However, no anatomical asymmetry
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between upper and lower jaw width has been found.
If one is proposing that the described para-facets in molars can be produced by the individual
us
occlusal movements in a typical crossbite situation, as it is suggested by Sarig and Tillier (2014), it is important to discuss and explain the development of the prominent incursive facets 5 and 6 (Fig. 1; see also Fig. 4 in Fiorenza and Kullmer, 2013) on the lingual slopes of the protocone and
an
on the Carabelli’s cusps. Facet 5 and 6 usually develop through attritional contacts with the metaconid disto-lingual slope (facet 5) and the entoconid mesio-lingual slope of the lower
M
antagonistic molar. The exact position to the complementary cusp slopes could probably be mesially or distally shifted, depending on the Angle Class relationship. In a crossbite situation,
d
however, it is highly unlikely to find strong facets 5 and 6 in the upper molars due to occlusal movements. Figure 2 shows three-dimensional virtual models of the antagonistic dental arches of
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a modern Homo sapiens affected by a posterior crossbite on the left side. The colored tooth contacts in maximum intercuspation (orange and red areas) are generated by the occlusal
Ac ce p
collision detection OFA software (Kullmer et al., 2013) and are showing typical differences in the contact situations. On the left side, there are no phase I contacts found on the buccal slopes of the protoconid and the hypoconid in the lower molars (red arrows) nor on the lingual slopes of the protocone in the upper molars (areas of facet 5 and 6; red arrow). In contrast, these contacts are present in a normal occlusal relationship on the right side (green arrows). Finally, Sarig and Tillier (2014) stated that the identification and labeling of wear facets in individuals with an Angle Class II, such as Qafzeh 9, through Maier and Schneck’s system (1981) is subjected to bias, and that it should be applied only to individuals with a normal occlusion. Before drawing such a sweeping conclusion, the authors need to show more convincing evidence for it. Qualitative observations based on only a few individuals (three), however, do not justify the use of different labelling systems according to the type of Angle Class occlusion.
Page 6 of 12
Acknowledgments The authors thank curators and institutions for access to the AMH sample: Yoel Rak (University of Tel Aviv, Israel) and Erik Trinkaus (Washington University, Saint Louis, MO).
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Moreover, the authors also thank Iva Nikolic for copyediting the manuscript and Christine Hemm for technical assistance. The authors also thank the two anonymous reviewers whose comments
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have helped improving this manuscript. This study was supported by the University of New
England (UNE Research Seed Grant 2014) and the Deutsche Forschungsgemeinschaft (DFG,
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German Research Foundation): publication no. 78 of the DFG Research Unit 771 ‘Function and performance enhancement in the mammalian dentition - phylogenetic and ontogenetic impact on
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the masticatory apparatus’.
References
Begg, P.R., 1954. Stone Age man’s dentition with reference to anatomically correct occlusion,
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the etiology of malocclusion, and a technique for its treatment. Am. J. Orthod. 40, 298-312. Begg, P.R., Kesling, P.C., 1977. Begg Orthodontic Theory and Technique, 3rd ed. Saunders,
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Philadelphia.
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Corruccini, R.S., 1984. An epidemiological transition in dental occlusion in world populations. Am. J. Orthod. 86, 419-426.
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Corruccini, R.S., Pacciani, E., 1989. “Orthodontistry” and dental occlusion in Etruscans. The Angle Orthodontist 59, 61-64.
Douglas, G.D., DeVreugd R.T., 1997. The dynamics of occlusal relationships. In: McNeill, C. (Ed.), Science and Practice of Occlusion. Quintessence Publishing Co, Illinois, pp. 69-78. Eshed, V., Gopher, A., Hershkovitz, I., 2006. Tooth wear and dental pathology at the advent of agriculture: new evidence from the Levant. Am. J. Phys. Anthropol. 134,145-159. Every, R.G., 1972. A New Terminology for Mammalian Teeth: Founded on the Phenomenon of Thegosis. Parts 1 and 2. Pegasus, Christchurch. Fiorenza, L., Benazzi, S., Kullmer, O., 2011a. Para-masticatory wear facets and their functional significance in huntergatherer maxillary molars. J. Archaeol. Sci. 38, 2182–2189. Fiorenza, L., Kullmer, O., 2013. Dental wear and cultural behavior in Middle Paleolithic humans from the Near East. Am. J. Phys. Anthropol. 152,107–117. Frayer, D.W., Russell, M.D., 1987. Artificial grooves on the Krapina Neanderthal teeth. Am. J.
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Phys. Anthropol. 74, 393-405. Harris, E.F., Corruccini, E., 2008. Quantification of dental occlusal variation: a review of methods. Dent. Anthropol. 21, 1-11. Hunt, E.E., 1961. Malocclusion and civilization. Am. J. Orthod. 47, 406-422.
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Kaidonis, J.A., 2008. Tooth wear: the view of the anthropologist. Clin. Oral. Invest. 12, Suppl. 1, 21-26.
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Kaifu, Y., Kasai, K., Townsend, G.C., Richards, L.C., 2003. Tooth wear and the design of the human dentition: A perspective from evolutionary medicine. Yrbk Phys. Anthropol. 46, 47-61.
us
Kullmer, O., Benazzi, S., Fiorenza, L., Schulz, D., Bacso, S., Winzen, O., 2009. Technical note: occlusal fingerprint analysis: quantification of tooth wear pattern. Am. J. Phys. Anthropol. 139, 600-605.
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Kullmer, O., Schulz, D., Benazzi, S., 2012. An experimental approach to evaluate the correspondence between wear facet position and occlusal movements. Anat. Rec. 295, 846-
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852.
Kullmer, O., Benazzi, S., Schulz, D., Gunz, P., Kordos, L., Begun, D.R., 2013. Dental arch
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restoration using tooth macrowear patterns with application to Rudapithecus hungaricus, from the late Miocene of Rudabánya, Hungary. J. Hum. Evol. 64, 151-160. Anthropol. 34, 27-42.
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Molnar, S., 1971. Human tooth wear, tooth function and cultural variability. Am. J. Phys.
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Molnar, S., 1972. Tooth wear and culture: a survey of tooth functions among some prehistoric populations. Curr. Anthropol. 13, 511-526. Nerder, P.H., Bakke, M., Solow, B., 1999. The functional shift of the mandible in unilateral posterior crossbite and the adaptation of the temporomandibular joints: a pilot study. Eur. J. Orthodont. 21, 155-166.
Radovčic J., Smith, F.H., Trinkaus, E., Wolpoff, M.H., 1988. The Krapina Hominids. An Illustrated Catalog of Skeletal Collection. Croatian Natural History Museum, Zagreb. Sarig, R., SLon, V., Abbas, J., May, H., Shpack, N., Vardimon, A.D., Hershkovits, I., 2013. Malocclusion in early anatomically modern human: a reflection on the etiology of modern dental misalignment. PLOS ONE 8 (11), e80771. Sarig, R., Tillier, A.M., 2014. Reconstructing cultural behavior from dental wear studies: Is parafacets analysis approach scientifically valid? Homo – J. Comp. Hum. Biol. 65, 181-186.
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Smith, B.H., 1984. Patterns of molar wear in hunter-gatherers and agriculturists. Am. J. Phys. Anthropol. 63, 39-56. Tollaro, I., Defraia, E., Marinelli, A., Alarashi, M., 2002. Tooth abrasion in unilateral posterior crossbite in the deciduous dentition. Angle Orthodontist 72, 426-430.
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Varrela, J., 2006. Masticatory function and malocclusion: a clinical perspective. Semin. Orthod. 12, 102-109.
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Veli, I., Uysal, T., Ozer, T., Ucar F.I., Eruz, M., 2011. Mandibular asymmetry in unilateral and bilateral posterior crossbite patients using cone-beam computed tomography. Angle
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Orthodontist 81, 966-974.
Wolpoff, M.H., 1978. The dental remains from Krapina. In: Malez, M., (Ed.), Krapinski Pračovjek I Evolucija Hominida. Yugoslav Academy of Sciences and Arts, Zagreb, pp. 119-
an
144.
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Legends for Figures
Fig. 1. Three-dimensional digital models of the right deciduous and permanent maxillary molars of Qafzeh 15, showing their wear patterns. Occlusal movements: Lateroretrusion (in blue; facets
d
1, 1.1, 4, 5, 5.1 and 8), Lateroprotrusion (in yellow; facets 2, 2.1, 3, 5, 5.1, 6 and 7), Mediotrusion
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and immediate sideshift (in green; facets 9, 11 and 12), medioprotrusion (in orange; facets 10 and
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13), para-facets (in light blue; facets P1 and P2). Fig. 2. Three-dimensional digital models of upper and lower dental arches of modern Homo sapiens affected by posterior crossbite on the left side. Tooth contacts in maximum intercuspation are colored in red and orange. In this case, usually there are no phase I contact facets observable on the buccal slopes of the protoconid and the hypoconid in the lower molars (red arrows – right side of the picture). Complementary facets on the palatinal slope of the protocone in the upper molars are not detectable (red arrow – right side of the picture), such as they can be found on the right side (green arrows – left side of the picture). Images extracted from Occlusal Fingerprint Analyser software (Kullmer et al., 2013).
Page 9 of 12
Table 1. List of Skhul and Qafzeh specimens analyzed in the previous study (Fiorenza and (N PF) per individual.
N PF 1 0 1 3 1 1 1 4 4 0 4 4
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Tooth type* ULM1, ULM3 ULM1, URM1 ULM1, ULM2, URM1, URM2, URM3 ULM1, ULM2, ULM3, URM1, URM2, URM3 URM1 ULM1, ULM2, ULM3, URM1, URM2, URM3 ULM1, ULM2, ULM3, URM1, URM2, URM3 ULdm1, ULdm2, ULM1, URdm1, URdm2, URM1 ULM1, ULM2, ULM3, URM1, URM2, URM3 URM3 ULM1, ULM2, ULM3, URM1, URM2, URM3 ULM1, ULM2, ULM3, URM1, URM2, URM3
us
N teeth 2 2 5 6 1 6 6 6 6 1 6 6
an
Specimens Qafzeh 3 Qafzeh 5 Qafzeh 6 Qafzeh 7 Qafzeh 8 Qafzeh 9 Qafzeh 11 Qafzeh 15 Qafzeh 27 Skhul 2 Skhul 4 Skhul 5
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Kullmer, 2013), including the number of teeth (N), the tooth type and the number of para-facets
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te
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*In bold the teeth with para-facets.
Page 10 of 12
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Fig. 1
Page 11 of 12
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Fig. 2
Page 12 of 12
S0018-442X(15)00043-8 http://dx.doi.org/doi:10.1016/j.jchb.2015.04.002 JCHB 25393
To appear in: Received date: Accepted date:
17-11-2014 14-4-2015
Please cite this article as: Fiorenza, L., Kullmer, O.,Dental wear patterns in early modern humans from Skhul and Qafzeh: A response to Sarig and Tillier, Journal of Comparative Human Biology (2015), http://dx.doi.org/10.1016/j.jchb.2015.04.002 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Dental wear patterns in early modern humans from Skhul and Qafzeh: A response to Sarig and Tillier Luca Fiorenzaa,b*, Ottmar Kullmerc a
ip t
Earth Sciences, University of New England, Armidale NSW 2351, Australia Department of Anatomy and Developmental Biology, Monash University, Melbourne VIC 3800, Australia c Senckenberg Research Institute, Senckenberganlage 25, 60325 Frankfurt am Main, Germany
an
us
cr
b
te
d
M
Received 17 November 2014; accepted 14 April 2015
Ac ce p
*Corresponding author. Tel.: +61 2 6773 2357, fax: +61 2 6773 3030. Email address: [email protected] (Luka Fiorenza)
Page 1 of 12
ip t
Abstract
cr
The use of teeth as tools for manipulating objects and simple food-processing methods was common among prehistoric and modern hunter-gatherer human populations. Paramasticatory
us
uses of teeth frequently produce enamel chipping and distinctive types of dental wear that can readily be related to specific tool functions. In particular, the presence of unusual occlusal wear
an
areas (named para-facets) on maxillary teeth of prehistoric, historic and modern hunter-gatherers has been associated with cultural habits involving extensive use of teeth (Fiorenza et al., 2011;
M
Fiorenza and Kullmer, 2013). However, Sarig and Tillier (2014) believe that this wear had been caused by pathological occlusal relationships rather than by the use of teeth as tools. In this contribution, we show how occlusal contacts are created and how it is possible to distinguish
d
between masticatory and non-masticatory wear facets by using an innovative digital approach
te
called Occlusal Fingerprint Analysis. Statistical results from the analysis of comparative modern samples clearly demonstrate that described para-facets in Skhul and Qafzeh could not have been
Ac ce p
produced by dental occlusal anomalies such as malocclusions and crossbites. Moreover, dental pathologies in prehistoric humans were extremely rare. Only with the adoption of the modern lifestyle between 18th and 19th centuries, did the emergence of malocclusions become significantly more common. Because more than 50% of the Skhul and Qafzeh individuals analysed in our study is characterised by this distinctive type of wear, it is highly unlikely that their para-facets occurred as a result of dental pathologies.
Introduction In a recent article, Sarig and Tillier (2014) questioned if the analysis of non-masticatory dental wear facets (here called para-facets) can effectively be used to reconstruct the cultural behaviour in extinct human populations. In their contribution they particularly refer to a previous study where para-facets have been recognised in the dentition of early modern humans from Skhul and
Page 2 of 12
Qafzeh (Fiorenza and Kullmer, 2013). According to Sarig and Tillier (2014), these wear areas are not created by non-masticatory habits, such as the use of teeth as tools, but are the product of Angle Class II malocclusion (Qafzeh 9) and crossbite (Qafzeh 11 and 15). In this response, we will address some of the arguments posited by Sarig and Tillier (2014) on
ip t
dynamic occlusion in prehistoric human populations.
cr
Analysis of fragmentary human fossil remains
Sarig and Tillier (2014) argued that the identification of para-facets should not be carried out
us
in the presence of isolated teeth, or in general when the antagonist teeth are absent, because wear facets are created by the contacts between upper and lower teeth, and the creation and appearance
an
of wear facets depend on the antagonistic relationship (e.g., Every, 1972, Kaidonis, 2008, Kullmer et al., 2009). The human fossil record is usually fragmentary and most often constituted of isolated teeth, e.g. as in the case of Neanderthal dental remains from Krapina (Radovčić et al.,
M
1988; Wolpoff, 1978). To overcome this problem and make the interpretation of results more robust, biological anthropologists commonly use modern comparative groups. Similarly, we have
d
initially tested if this unusual type of dental wear facets can be the result of a normal masticatory behaviour by analysing a modern human sample of upper and lower teeth with reproducible
te
occlusal pathways and distinctive antagonistic contacts (Fiorenza et al., 2011). In this study we
Ac ce p
found that almost none of the specimens (94.1%) characterized by this type of wear exhibit complementary wear facets on the lower teeth. Each wear facet identifiable in the upper teeth must leave a matching facet in the opposing lower dental arch (e.g., Every, 1972; Kaidonis, 2008). Statistically significant absence of matching facets in the lower teeth led us to conclude that this unusual type of wear was not created by a normal chewing behaviour (Fiorenza et al., 2011).
Occlusal Fingerprint Analysis (OFA) method To further corroborate our initial explanation we have created a three-dimensional (3D) occlusal compass for each tooth analysed in order to quantitatively describe the major occlusal movements responsible for the creation of wear facets (Kullmer et al., 2009, 2012). Starting from a position of centric occlusion (maximal intercuspation), the dental occlusal concept identifies five major mandibular movements (Douglass and DeVreugd, 1997).
Page 3 of 12
The spatial directions of the para-facets found in some modern human specimens and in the Skhul and Qafzeh groups do not statistically fall within any of the mandibular directions described by the dental occlusal concept. The only reasonable explanation for their formation is a non-occlusal creation, such as the use of teeth as a tool (Fiorenza et al., 2011). Observations of
ip t
Middle Palaeolithic humans from the Levant showed that this unique type of wear in the upper molars was remarkably frequent (52.2%). Absence of complementary contacts in the lower teeth
cr
and the occlusal compass analyses confirmed that these wear areas could not have been created by normal masticatory behaviour but were most likely caused by tooth-tool uses (Fiorenza and
us
Kullmer, 2013). These results are not surprising. There is overwhelming evidence showing how prehistoric and historic human populations used their teeth as tools for tearing, holding and manipulating a variety of objects (Eshed et al., 2006; Frayer and Russell, 1987; Molnar, 1971,
an
1972; Smith, 1984).
Consequently, our results are in disagreement with Sarig and Tillier (2014) when they
M
question if the analytic approach in Fiorenza and Kullmer (2013) study was scientifically valid; while Sarig and Tillier’s (2014) interpretation is only based on qualitative observations of three
d
individuals, our approach is centred on quantitative measurements and statistically robust method, which we used to analyse and compare 35 modern hunter-gatherer individuals and 158
Ac ce p
te
human fossil specimens (Fiorenza et al., 2011; Fiorenza and Kullmer, 2013).
Misinterpretations of results
Another major aspect to consider in the study of Sarig and Tillier (2014) is their misinterpretation of the results and conclusions drawn by Fiorenza and Kullmer (2013). While it is true that in the latter contribution it was hypothesised that the presence of para-facets in Near Eastern Neanderthals and anatomically modern humans could have been interpreted as evidence for cultural interaction, this was only one of the two explanations proposed. We formulated two distinct and exclusive hypotheses: 1) independent cultural habits, and 2) possible cultural interactions. Sarig and Tillier (2014) also mistakenly analysed and discussed the interpretation of the presumed para-facets on first maxillary molars of the specimen Qafzeh 15, where we found parafacets only on the deciduous molars (see Table 1 in Fiorenza and Kullmer, 2013) and not on the M1 (Fig. 1).
Page 4 of 12
To avoid further confusion, we include here a table that contains all the specimens analysed in the previous study (Fiorenza and Kullmer, 2013), clearly showing which maxillary molars displayed para-facets and which not (Table 1).
ip t
Frequency of malocclusions in prehistoric human populations
An increase in malocclusion took place relatively recently, between 18th – 19th centuries with
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the adoption of modern lifestyles (e.g. Varrela, 2006). It is believed that the introduction of soft and energy-rich foodstuffs in the daily diet caused a strong reduction of the masticatory forces,
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decreasing the number of chewing cycles and consequently shortening the duration of mastication (Corruccini, 1984). The decrease in masticatory-functional demands has brought
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about disequilibrium in the dynamic relationships between occlusion and dentition, causing an increase in occlusal variation characterized by misalignment of teeth (Begg, 1954; Begg and Kiesling, 1977; Corrucini, 1984; Kaifu et al., 2003; Varrela, 2006). Malocclusions, however,
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were extremely rare in archaic humans (Begg, 1954; Begg and Kesling, 1977; Corruccini and Pacciani, 1989; Hunt, 1961; Kaifu et al., 2003).
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We do not disregard that Qafzeh 9 is characterized by a crossbite in the left anterior dentition in the position of the left I2. However, the presence of a real posterior crossbite is questionable
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and cannot be related to the development of para-facets in the upper molars. If we associated the
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presence of presumed para-facets with malocclusion, as interpreted for Qafzeh 9, 11 and 15 by Sarig and Tiller (2014), we would expect that the early modern human populations from Skhul and Qafzeh frequently displayed misalignment of teeth (> 50%), an unmatched result in any known prehistoric human population. It is therefore highly unlikely that the para-facets found in the upper molars are the product of malocclusion, such as edge-to-edge occlusion and crossbite, as suggested by Sarig et al. (2013) and Sarig and Tillier (2014). While these authors showed possible contact between para-facets and lower teeth in Qafzeh 11 and 15 (Figs. 2 and 3; Sarig and Tillier, 2014), they did not illustrate any contact details nor the existence of the complementary wear facets on the occlusal surface of the lower crowns. Moreover, a posterior crossbite commonly occurs when the buccal cusps of the maxillary teeth occlude lingually to the buccal cusps of the corresponding mandibular teeth (Harris and Corruccini, 2008; Nerder et al., 1999). In modern westernised societies posterior crossbite is common in the early stages of development, usually producing a lateral shift on one side of the mandible (or unilateral
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crossbite) (Tollaro et al., 2002). The much less common bilateral crossbite usually results in asymmetrical mandibles (Veli et al., 2011). In our early modern human sample we found that three specimens from Qafzeh and two specimens from Skhul show para-facets on both sides of the jaw (Table 1). In this particular
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scenario, if we hypothesised that the attritional facets are caused by malocclusion, we would expect to find the unusual cases of bilateral crossbite. However, no anatomical asymmetry
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between upper and lower jaw width has been found.
If one is proposing that the described para-facets in molars can be produced by the individual
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occlusal movements in a typical crossbite situation, as it is suggested by Sarig and Tillier (2014), it is important to discuss and explain the development of the prominent incursive facets 5 and 6 (Fig. 1; see also Fig. 4 in Fiorenza and Kullmer, 2013) on the lingual slopes of the protocone and
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on the Carabelli’s cusps. Facet 5 and 6 usually develop through attritional contacts with the metaconid disto-lingual slope (facet 5) and the entoconid mesio-lingual slope of the lower
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antagonistic molar. The exact position to the complementary cusp slopes could probably be mesially or distally shifted, depending on the Angle Class relationship. In a crossbite situation,
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however, it is highly unlikely to find strong facets 5 and 6 in the upper molars due to occlusal movements. Figure 2 shows three-dimensional virtual models of the antagonistic dental arches of
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a modern Homo sapiens affected by a posterior crossbite on the left side. The colored tooth contacts in maximum intercuspation (orange and red areas) are generated by the occlusal
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collision detection OFA software (Kullmer et al., 2013) and are showing typical differences in the contact situations. On the left side, there are no phase I contacts found on the buccal slopes of the protoconid and the hypoconid in the lower molars (red arrows) nor on the lingual slopes of the protocone in the upper molars (areas of facet 5 and 6; red arrow). In contrast, these contacts are present in a normal occlusal relationship on the right side (green arrows). Finally, Sarig and Tillier (2014) stated that the identification and labeling of wear facets in individuals with an Angle Class II, such as Qafzeh 9, through Maier and Schneck’s system (1981) is subjected to bias, and that it should be applied only to individuals with a normal occlusion. Before drawing such a sweeping conclusion, the authors need to show more convincing evidence for it. Qualitative observations based on only a few individuals (three), however, do not justify the use of different labelling systems according to the type of Angle Class occlusion.
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Acknowledgments The authors thank curators and institutions for access to the AMH sample: Yoel Rak (University of Tel Aviv, Israel) and Erik Trinkaus (Washington University, Saint Louis, MO).
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Moreover, the authors also thank Iva Nikolic for copyediting the manuscript and Christine Hemm for technical assistance. The authors also thank the two anonymous reviewers whose comments
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have helped improving this manuscript. This study was supported by the University of New
England (UNE Research Seed Grant 2014) and the Deutsche Forschungsgemeinschaft (DFG,
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German Research Foundation): publication no. 78 of the DFG Research Unit 771 ‘Function and performance enhancement in the mammalian dentition - phylogenetic and ontogenetic impact on
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the masticatory apparatus’.
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the etiology of malocclusion, and a technique for its treatment. Am. J. Orthod. 40, 298-312. Begg, P.R., Kesling, P.C., 1977. Begg Orthodontic Theory and Technique, 3rd ed. Saunders,
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Philadelphia.
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Corruccini, R.S., 1984. An epidemiological transition in dental occlusion in world populations. Am. J. Orthod. 86, 419-426.
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Corruccini, R.S., Pacciani, E., 1989. “Orthodontistry” and dental occlusion in Etruscans. The Angle Orthodontist 59, 61-64.
Douglas, G.D., DeVreugd R.T., 1997. The dynamics of occlusal relationships. In: McNeill, C. (Ed.), Science and Practice of Occlusion. Quintessence Publishing Co, Illinois, pp. 69-78. Eshed, V., Gopher, A., Hershkovitz, I., 2006. Tooth wear and dental pathology at the advent of agriculture: new evidence from the Levant. Am. J. Phys. Anthropol. 134,145-159. Every, R.G., 1972. A New Terminology for Mammalian Teeth: Founded on the Phenomenon of Thegosis. Parts 1 and 2. Pegasus, Christchurch. Fiorenza, L., Benazzi, S., Kullmer, O., 2011a. Para-masticatory wear facets and their functional significance in huntergatherer maxillary molars. J. Archaeol. Sci. 38, 2182–2189. Fiorenza, L., Kullmer, O., 2013. Dental wear and cultural behavior in Middle Paleolithic humans from the Near East. Am. J. Phys. Anthropol. 152,107–117. Frayer, D.W., Russell, M.D., 1987. Artificial grooves on the Krapina Neanderthal teeth. Am. J.
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Kaidonis, J.A., 2008. Tooth wear: the view of the anthropologist. Clin. Oral. Invest. 12, Suppl. 1, 21-26.
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Kaifu, Y., Kasai, K., Townsend, G.C., Richards, L.C., 2003. Tooth wear and the design of the human dentition: A perspective from evolutionary medicine. Yrbk Phys. Anthropol. 46, 47-61.
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Kullmer, O., Benazzi, S., Fiorenza, L., Schulz, D., Bacso, S., Winzen, O., 2009. Technical note: occlusal fingerprint analysis: quantification of tooth wear pattern. Am. J. Phys. Anthropol. 139, 600-605.
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Kullmer, O., Schulz, D., Benazzi, S., 2012. An experimental approach to evaluate the correspondence between wear facet position and occlusal movements. Anat. Rec. 295, 846-
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Kullmer, O., Benazzi, S., Schulz, D., Gunz, P., Kordos, L., Begun, D.R., 2013. Dental arch
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restoration using tooth macrowear patterns with application to Rudapithecus hungaricus, from the late Miocene of Rudabánya, Hungary. J. Hum. Evol. 64, 151-160. Anthropol. 34, 27-42.
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Molnar, S., 1971. Human tooth wear, tooth function and cultural variability. Am. J. Phys.
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Molnar, S., 1972. Tooth wear and culture: a survey of tooth functions among some prehistoric populations. Curr. Anthropol. 13, 511-526. Nerder, P.H., Bakke, M., Solow, B., 1999. The functional shift of the mandible in unilateral posterior crossbite and the adaptation of the temporomandibular joints: a pilot study. Eur. J. Orthodont. 21, 155-166.
Radovčic J., Smith, F.H., Trinkaus, E., Wolpoff, M.H., 1988. The Krapina Hominids. An Illustrated Catalog of Skeletal Collection. Croatian Natural History Museum, Zagreb. Sarig, R., SLon, V., Abbas, J., May, H., Shpack, N., Vardimon, A.D., Hershkovits, I., 2013. Malocclusion in early anatomically modern human: a reflection on the etiology of modern dental misalignment. PLOS ONE 8 (11), e80771. Sarig, R., Tillier, A.M., 2014. Reconstructing cultural behavior from dental wear studies: Is parafacets analysis approach scientifically valid? Homo – J. Comp. Hum. Biol. 65, 181-186.
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Smith, B.H., 1984. Patterns of molar wear in hunter-gatherers and agriculturists. Am. J. Phys. Anthropol. 63, 39-56. Tollaro, I., Defraia, E., Marinelli, A., Alarashi, M., 2002. Tooth abrasion in unilateral posterior crossbite in the deciduous dentition. Angle Orthodontist 72, 426-430.
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Varrela, J., 2006. Masticatory function and malocclusion: a clinical perspective. Semin. Orthod. 12, 102-109.
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Veli, I., Uysal, T., Ozer, T., Ucar F.I., Eruz, M., 2011. Mandibular asymmetry in unilateral and bilateral posterior crossbite patients using cone-beam computed tomography. Angle
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Orthodontist 81, 966-974.
Wolpoff, M.H., 1978. The dental remains from Krapina. In: Malez, M., (Ed.), Krapinski Pračovjek I Evolucija Hominida. Yugoslav Academy of Sciences and Arts, Zagreb, pp. 119-
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144.
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Legends for Figures
Fig. 1. Three-dimensional digital models of the right deciduous and permanent maxillary molars of Qafzeh 15, showing their wear patterns. Occlusal movements: Lateroretrusion (in blue; facets
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1, 1.1, 4, 5, 5.1 and 8), Lateroprotrusion (in yellow; facets 2, 2.1, 3, 5, 5.1, 6 and 7), Mediotrusion
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and immediate sideshift (in green; facets 9, 11 and 12), medioprotrusion (in orange; facets 10 and
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13), para-facets (in light blue; facets P1 and P2). Fig. 2. Three-dimensional digital models of upper and lower dental arches of modern Homo sapiens affected by posterior crossbite on the left side. Tooth contacts in maximum intercuspation are colored in red and orange. In this case, usually there are no phase I contact facets observable on the buccal slopes of the protoconid and the hypoconid in the lower molars (red arrows – right side of the picture). Complementary facets on the palatinal slope of the protocone in the upper molars are not detectable (red arrow – right side of the picture), such as they can be found on the right side (green arrows – left side of the picture). Images extracted from Occlusal Fingerprint Analyser software (Kullmer et al., 2013).
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Table 1. List of Skhul and Qafzeh specimens analyzed in the previous study (Fiorenza and (N PF) per individual.
N PF 1 0 1 3 1 1 1 4 4 0 4 4
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Tooth type* ULM1, ULM3 ULM1, URM1 ULM1, ULM2, URM1, URM2, URM3 ULM1, ULM2, ULM3, URM1, URM2, URM3 URM1 ULM1, ULM2, ULM3, URM1, URM2, URM3 ULM1, ULM2, ULM3, URM1, URM2, URM3 ULdm1, ULdm2, ULM1, URdm1, URdm2, URM1 ULM1, ULM2, ULM3, URM1, URM2, URM3 URM3 ULM1, ULM2, ULM3, URM1, URM2, URM3 ULM1, ULM2, ULM3, URM1, URM2, URM3
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N teeth 2 2 5 6 1 6 6 6 6 1 6 6
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Specimens Qafzeh 3 Qafzeh 5 Qafzeh 6 Qafzeh 7 Qafzeh 8 Qafzeh 9 Qafzeh 11 Qafzeh 15 Qafzeh 27 Skhul 2 Skhul 4 Skhul 5
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Kullmer, 2013), including the number of teeth (N), the tooth type and the number of para-facets
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*In bold the teeth with para-facets.
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Fig. 1
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Fig. 2
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