458 research outputs found
3D enamel thickness in Neandertals and Homo sapiens permanent lower canines
No full textOver the last decades, the growing support of 3D data has led to develop comparative morphometric and qualitative methods to
increase the number of fossils suitable for more comprehensive dental analysis [1]. Enamel thickness figures prominently in studies
of human evolution, particularly with hominoid taxonomy, phylogeny, and paleodiet [2, 3]. Attention has focused on molar
teeth, recently utilising advanced technologies with novel protocols [3]. Despite important results achieved thus far, further work
is needed to investigate all tooth classes. We apply a recent approach developed for anterior teeth [4] to investigate 3D enamel
thickness of hominin canines. MicroCT data of 38 unworn/lightly worn Homo sapiens (Early: n= 4; Upper Paleolithic: n=4; Recent:
n=21) and Neandertal (n=9) permanent lower canines were segmented using Avizo 7 to reconstruct 3D digital models of the
teeth. The cervical line was digitized on each 3D model using the spline function in Rapidform XOR to separate crown from root
dentine. Volumes of enamel and of crown dentine, and the enamel-dentine junction surface were measured to compute Relative
Enamel Thickness (RET). Mean RET value for Neandertals (12.7±1.8) falls below the mean computed for H. sapiens (Upper Paleolithic=
15.6±2.9; Early=14.0±1.9; Recent=15.5±2.6). Results of the permutation test between Neandertal and recent humans
support the significant difference in RET (p=0.0055), a useful index for the taxonomic discrimination between modern humans
and Neandertals. This preliminary study confirms this trend for lower permanent canines [2], using a 3D protocol which is reproducible,
has little subjectivity, and is particularly effective for the uneven contour of cervical enamel in anterior teeth. In recent
literature, although the majority of datasets are based on micro-CT scans, the analysis of dental tissues in Neandertal and H. sapiens
permanent lower canines have been performed on virtual longitudinal sections [2, 5]. Our preliminary 3D analysis of permanent
lower canines support the general findings that Neandertal have thinner enamel than H. sapiens, as observed in molars. Future
contributions will incorporate increased sample sizes and include worn teeth to investigate whether the RET index continues to
discriminate between Neandertal and H. sapiens canines.
Acknowledgements: We thank all the curators and collaborators that granted us access to the dental material and the CT-operators
at MPI-EVA.
References:[1] Le Cabec, A., Tang, N., Tafforeau, P., 2015. Accessing Developmental Information of Fossil Hominin Teeth
Using New Synchrotron-Microtomography Based Visualization Techniques of Dental Surfaces and Interfaces. PLoS ONE 10(4):
e0123019. doi:10.1371/journal.pone.0123019[2] Smith, T.M., Olejniczak, A.J., Zermeno, J.P., Tafforeau, P., Skinner, M.M.,
Hoffmann, A., Radovcic, J., Toussaint, M., Kruszynski, R., Menter, C., Moggi- Cecchi, J., Glasmacher, U.A., Kullmer, O.,
Schrenk, F., Stringer, C., Hublin, J.-J., 2012. Variation in enamel thickness within the genus Homo. J. Hum. Evol. 62,395e411.[3]
Olejniczak, A.J., Smith, T.M., Feeney, R.N.M., Macchiarelli, R., Mazurier, A.,Bondioli, L., Rosas, A., Fortea, J., de la Rasilla, M.,
Garcia-Tabernero, A., Radovcic, J., Skinner, M.M., Toussaint, M., Hublin, J.-J., 2008. Dental tissue proportions and enamel
thickness in Neandertal and modern human molars. J. Hum. Evol. 55, 12e23.[4] Benazzi, S., Panetta, D., Fornai, C., Toussaint,
M., Gruppioni, G., Hublin, J-J., 2014. Technical Note: Guidelines for the digital computation of 2D and 3D enamel thickness in
hominoid teeth. Am. J. Phys. Anthropol. 2014 Feb;153(2):305-13.[5] Feeney, R.N.M., Zermeno, J.P., Reid, D.J., Nakashima, S.,
Sano, H., Bahar, A., Hublin, J-J., Smith, T.S., 2010. ’Enamel thickness in Asian human canines and premolars’. Anthrop. Sci., 118
(3):191-198
Bulletins et Mémoires de la Société d'Anthropologie de Paris, n.s., 1989, I (3-4), n° spéc. : Histoire de l'anthropologie : hommes idées, moments. S. dir. C. Blanckaert, A. Ducros & J.-J. Hublin
No full textMasset Claude. Bulletins et Mémoires de la Société d'Anthropologie de Paris, n.s., 1989, I (3-4), n° spéc. : Histoire de l'anthropologie : hommes idées, moments. S. dir. C. Blanckaert, A. Ducros & J.-J. Hublin. In: L'Homme, 1992, tome 32 n°121. Anthropologie du proche. pp. 238-239
Unravelling the functional biomechanics of dental features and tooth wear
No full textMost of the morphological features recognized in hominin teeth, particularly the topography of the occlusal surface, are generally interpreted as an evolutionary functional adaptation for mechanical food processing. In this respect, we can also expect that the general architecture of a tooth reflects a response to withstand the high stresses produced during masticatory loadings. Here we use an engineering approach, finite element analysis (FEA), with an advanced loading concept derived from individual occlusal wear information to evaluate whether some dental traits usually found in hominin and extant great ape molars, such as the trigonid crest, the entoconid-hypoconulid crest and the protostylid have important biomechanical implications. For this purpose, FEA was applied to 3D digital models of three Gorilla gorilla lower second molars (M2) differing in wear stages. Our results show that in unworn and slightly worn M2s tensile stresses concentrate in the grooves of the occlusal surface. In such condition, the trigonid and the entoconid-hypoconulid crests act to reinforce the crown locally against stresses produced along the mesiodistal groove. Similarly, the protostylid is shaped like a buttress to suffer the high tensile stresses concentrated in the deep buccal groove. These dental traits are less functional in the worn M2, because tensile stresses decrease physiologically in the crown with progressing wear due to the enlargement of antagonistic contact areas and changes in loading direction from oblique to nearly parallel direction to the dental axis. This suggests that the wear process might have a crucial influence in the evolution and structural adaptation of molars enabling to endure bite stresses and reduce tooth failure throughout the lifetime of an individual
The effectiveness of using carbonate isotope measurements of body tissues to infer diet in human evolution: Evidence from wild western chimpanzees (Pan troglodytes verus)*
No full textChanges in diet throughout hominin evolution have been linked with important evolutionary changes. Stable carbon isotope analysis of inorganic apatite carbonate is the main isotopic method used to reconstruct fossil hominin diets; to test its effectiveness as a paleodietary indicator we present bone and enamel carbonate carbon isotope data from a well-studied population of modern wild western chimpanzees (Pan troglodytes verus) of known sex and age from Taï, Cote d'Ivoire.We found a significant effect of age class on bone carbonate values, with adult chimpanzees being more 13C- and 18O-depleted compared to juveniles. Further, to investigate habitat effects, we compared our data to existing apatite data on eastern chimpanzees (P. troglodytes schweinfurthii) and found that the Taï chimpanzees are significantly more depleted in enamel d13Cap and d18Oap compared to their eastern counterparts. Our data are the first to present a range of tissue-specific isotope data from the same group of wild western chimpanzees and, as such, add new data to the growing number of modern non-human primate comparative isotope datasets providing valuable information for the interpretation of diet throughout hominin evolution. By comparing our data to published isotope data on fossil hominins we found that our modern chimpanzee bone and enamel data support hypotheses that the trend towards increased consumption of C4 foods after 4 Ma (millions of years ago) is unique to hominins
Self-reported sleep bruxism and mortality in 1990–2020 in a nationwide twin cohort
No full textBackground: The association of sleep bruxism with mortality has not been studied. Objectives: Altogether 12 040 subjects from the nationwide Finnish twin cohort were included in the analyses. We examined whether self-reported sleep bruxism is associated with increased risk of mortality, and if so, whether the effect is independent of known common risk factors. The time span of the follow-up was 30 years. Methods: Cox proportional hazards regression models (Hazard Ratios and their 95% Confidence Intervals) adjusted by age, sex and covariates were used to assess the effect of baseline bruxism status in 1990 on future mortality in 1990–2020. Results: The risk of mortality among all participants (n = 12 040), independent of missing covariates and adjusted by age and sex, was 40% higher in weekly bruxers than in never bruxers (HR 1.40, 95% CI 1.16–1.68, p <.001). However, when adjusted by all studied covariates, (n = 11 427) the risk was no longer observed (HR 1.04, 95% CI 0.86–1.25, p =.717). Despite the overall lack of between bruxism and mortality after adjustment for covariates, we examined the cause-specific risks for major cause-of-death groups. There were no substantial associations of weekly bruxism with major disease outcomes by the fully adjusted hazard ratios for them. Conclusion: Bruxism does not kill—in line with its definition of being rather a behaviour (with all its phenotypes) than a disease
Size matters: Radiocarbon dates of <200 μg ancient collagen samples with AixMICADAS and Its Gas Ion Source
No full textFor many of archaeology's rarest and most enigmatic bone artifacts (e.g. human remains, bone ornaments, worked bone), the destruction of the 500 mg material necessary for direct accelerator mass spectrometry (AMS) dating on graphite targets would cause irreparable damage; therefore many have not been directly dated. The recently improved gas ion source of the MICADAS (MIni CArbon DAting System) offers a solution to this problem by measuring gaseous samples of 5-100 μg carbon at a level of precision not previously achieved with an AMS gas ion source. We present the results of the first comparison between routine graphite dates of ca. 1000 μg C (2-3 mg bone collagen) and dates from aliquots of gaseous samples of <100 μg C (<0.2 mg bone collagen), undertaken with the highest possible precision in mind. The experiment demonstrates the performance of the AixMICADAS in achieving reliable radiocarbon measurements from <0.2 mg collagen samples back to 40,000 14C BP. The technique has great implications for resolving chronological questions for key archaeological artifacts
Correlates and genetics of self-reported sleep and awake bruxism in a nationwide twin cohort
No full text
The modern human colonization of western Eurasia: when and where?
No full textAbstractDating the timing of the replacement of local Neandertal populations by modern humans in western Eurasia at the dawn of the Upper Palaeolithic remains challenging due to the scarcity of the palaeontological evidence and to the complexity of the archaeological record. Furthermore, key specimens have been discovered in the course of excavations that unfortunately did not meet today's archaeological standards. The importance of site-formation processes in the considered time period makes it sometimes difficult to precisely assign fragmentary remains a posteriori to distinct techno-complexes. The improvements in dating methods have however allowed for the clarification of many chronological issues in the past decade. Archaeological and palaeontological evidence strongly suggest that the initial modern colonization of eastern Europe and central Asia should be related to the spread of techno-complexes assigned to the Initial Upper Palaeolithic. This first expansion may have started as early as 48 ka cal BP. The earliest phases of the Aurignacian complex (Protoaurignacian and Early Aurignacian) seem to represent another modern wave of migrations, starting in the Levant area. The expansion of this techno-complex throughout Europe completed the modern colonization of the continent. The interpretation of a third group of industries referred to as “transitional assemblages” in western and central Europe is much debated. At least in part, these assemblages might have been produced by Neandertal groups that may have survived until c. 41 ka cal BP, according to the directly dated Neandertal specimens of Saint-Césaire (France) and Spy (Belgium)
Pretreatment and gaseous radiocarbon dating of 40–100 mg archaeological bone
No full textRadiocarbon dating archaeological bone typically requires 300–1000 mg material using standard protocols. We report the results of reducing sample size at both the pretreatment and 14 C measurement stages for eight archaeological bones spanning the radiocarbon timescale at different levels of preservation. We adapted our standard collagen extraction protocol specifically for <100 mg bone material. Collagen was extracted at least twice (from 37–100 mg material) from each bone. Collagen aliquots containing <100 μg carbon were measured in replicate using the gas ion source of the AixMICADAS. The effect of sample size reduction in the EA-GIS-AMS system was explored by measuring 14 C of collagen containing either ca. 30 μg carbon or ca. 90 μg carbon. The gas dates were compared to standard-sized graphite dates extracted from large amounts (500–700 mg) of bone material pretreated with our standard protocol. The results reported here demonstrate that we are able to reproduce accurate radiocarbon dates from <100 mg archaeological bone material back to 40,000 BP
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