Article

How Neanderthal Molar Teeth Grew

Laboratoire de Géobiologie, Biochronologie et Paléontologie Humaine, UMR 6046 CNRS, Université de Poitiers, 86022 Poitiers, France.
Nature (Impact Factor: 41.46). 01/2007; 444(7120):748-51. DOI: 10.1038/nature05314
Source: PubMed

ABSTRACT

Growth and development are both fundamental components of demographic structure and life history strategy. Together with information about developmental timing they ultimately contribute to a better understanding of Neanderthal extinction. Primate molar tooth development tracks the pace of life history evolution most closely, and tooth histology reveals a record of birth as well as the timing of crown and root growth. High-resolution micro-computed tomography now allows us to image complex structures and uncover subtle differences in adult tooth morphology that are determined early in embryonic development. Here we show that the timing of molar crown and root completion in Neanderthals matches those known for modern humans but that a more complex enamel-dentine junction morphology and a late peak in root extension rate sets them apart. Previous predictions about Neanderthal growth, based only on anterior tooth surfaces, were necessarily speculative. These data are the first on internal molar microstructure; they firmly place key Neanderthal life history variables within those known for modern humans.

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    • "Moreover, we performed a geometric morphometric (GM) investigation of both inner and outer aspects of the crown based on 3D coordinate data. In particular, we considered the occlusal ridge at the EDJ since this feature might carry a taxonomic signal (e.g., Corruccini, 1987, 1998; Olejniczak et al., 2004, 2007; Macchiarelli et al., 2006; Skinner et al., 2009; Fornai et al., 2015). From the outer aspect, we analyzed the crown and cervical outlines of the dental crown (Benazzi et al., 2012, 2014a) in order also to include specimens showing moderate degree of occlusal wear in our comparative sample. "
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    ABSTRACT: The Qesem Cave Middle Pleistocene hominin site has yielded a well preserved lower second deciduous molar (dm2-QC2), among several other human dental remains. It has been previously described by Hershkovitz et al. using traditional methods. In this study, we used multiple approaches in order to characterize the outer and inner morphology of dm2-QC2, namely a descriptive investigation of the inner morphology, analysis of the dental tissues, and comparative 3D geometric morphometric investigation of various aspects of the dental crown based on data gathered from μCT images. Dm2-QC2 was compared to a sample of 44 specimens, including recent and fossil modern humans, Neanderthals, and Homo erectus.
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    • "This unique morphology differs from the lower, more squat cuspsTable 6 Maximum molar cuspal enamel extension rates in extant and fossil catarrhine primates (decreasing values).Tableau 6 Taux d'extension maximal de l'émail des cuspides des molaires chez des primates catarrhiniens actuels et fossiles (valeurs décroissantes). and dentine horns enclosing a sub-concave occlusal basin commonly seen in fossil and extant hominoid molars, such as Ouranopithecus (Macchiarelli et al., 2009 ), Paranthropus and Australopithecus (Skinner et al., 2008a), Homo (Macchiarelli et al., 2006; Skinner et al., 2008b; Zanolli, 2014; Zanolli and Mazurier, 2013), and in the living great apes (Skinner et al., 2008bSkinner et al., , 2010). Assuming that Oreopithecus is closely related to the dryopithecines (Harrison and Rook, 1997; Moyà-Solà and Köhler, 1997), which almost invariably exhibit a low to only moderately elevated external crown topography (Alba et al., 2013; Begun, 2002), its tall occlusal reliefs could represent an autapomorphic feature developed under conditions of insular isolation. "
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    • "We investigated two components of enamel microstructure of the Moula-Guercy remains: perikymata and linear enamel hypoplasia. Perikymata are enamel surface manifestations of internal growth increments known as striae of Retzius (Hillson, 1996) representing 7 or 8 days' worth of enamel growth in Neanderthals (Macchiarelli et al., 2006; Smith et al., 2009; Smith et al., 2010). Perikymata cover the surface of lateral enamel, forming shallow grooves or waves approximately 100 lm apart (Hillson and Bond, 1997). "

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