Geometric morphometric analysis of the crown morphology of the lower first premolar of hominins, with special attention to Pleistocene Homo

Centro Nacional de Investigación sobre Evolución Humana, Avda. de la Paz, 28, 09006, Burgos, Spain.
Journal of Human Evolution (Impact Factor: 3.73). 10/2008; 55(4):627-38. DOI: 10.1016/j.jhevol.2008.03.011
Source: PubMed

ABSTRACT This article is the third of a series that explores hominin dental crown morphology by means of geometric morphometrics. After the analysis of the lower second premolar and the upper first molar crown shapes, we apply the same technique to lower first premolar morphology. Our results show a clear distinction between the morphology seen in earlier hominin taxa such as Australopithecus and African early Homo, as well as Asian H. erectus, and more recent groups such as European H. heidelbergensis, H. neanderthalensis, and H. sapiens. The morphology of the earlier hominins includes an asymmetrical outline, a conspicuous talonid, and an occlusal polygon that tends to be large. The morphology of the recent hominins includes a symmetrical outline and a reduced or absent talonid. Within this later group, premolars belonging to H. heidelbergensis and H. neanderthalensis tend to possess a small and mesiolingually-displaced occlusal polygon, whereas H. sapiens specimens usually present expanded and centered occlusal polygons in an almost circular outline. The morphological differences among Paranthropus, Australopithecus, and African early Homo as studied here are small and evolutionarily less significant compared to the differences between the earlier and later homin taxa. In contrast to the lower second premolar and the upper first molar crown, the inclusion of a larger hominin sample of lower first premolars reveals a large allometric component.

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Available from: María Martinón-Torres, Sep 27, 2015
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    • "Shape information is extracted by removing any translational or rotational differences and then scaling to a best fit. Several authors emphasize the ability of geometric morphometric techniques to assess morphological differences precisely and have recommended the use of three-dimensional (3D) tools, avoiding possible complications derived from the analysis of 2D images (Gómez-Robles et al., 2007, 2008). "
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    ABSTRACT: Assessment of tooth morphology is an important part of the diagnosis and management of hypodontia patients. Several techniques have been used to analyze tooth form in hypodontia patients and these have shown smaller tooth dimensions and anomalous tooth shapes in patients with hypodontia when compared with controls. However, previous studies have mainly used 2D images and provided limited information. In the present study, 3D surface-imaging and statistical shape analysis were used to evaluate tooth form differences between hypodontia and control patients. Eighteen anatomical landmarks were recorded on the clinical crown of the lower left first permanent molar of 3D scanned study models of hypodontia and control subjects. The study sample group comprised of 120 hypodontia patients (40 mild, 40 moderate, and 40 severe hypodontia patients) and 40 age- and sex-matched controls. Procrustes coordinates were utilized to scale and superimpose the landmark coordinate data and then were subjected to principal component analysis (PCA). Subsequently, differences in shape as well as size were tested statistically using allometric analysis and MANOVA. Significant interaction was found between the two factor variables "group" and "sex" (p < 0.002). Overall expected accuracies were 66 and 56% for females and males, respectively, in the cross-validated discriminant-analysis using the first 20 PCs. Hypodontia groups showed significant shape differences compared with the control subjects (p < 0.0001). Significant differences in tooth crown shape were also found between sexes (p < 0.0001) within groups. Furthermore, the degree of variation in tooth form was proportional to the degree of the severity of the hypodontia. Thus, quantitative measurement of tooth shape in hypodontia patients may enhance the multidisciplinary management of those patients.
    Frontiers in Physiology 04/2014; 5:154. DOI:10.3389/fphys.2014.00154 · 3.53 Impact Factor
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    • "The intersection point between a fan line and the crown outline was treated as a semilandmark. For those teeth suffering from significant interproximal wear facets, the original crown outline was estimated by reference to overall shape of the preserved crown and the extent of the wear facets before the localization of semilandmarks (Wood and Uytterschaut, 1987; Gómez-Robles et al., 2008). A series of TPS software (Rohlf, 1998a, b, c) was employed to collect raw coordinate data of the landmarks and semilandmarks and to conduct superimposition and relative warp analyses (or principal component analysis). "
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    ABSTRACT: a b s t r a c t The hominin teeth and evidence of hominin activities recovered from 1991 to 2005 at the Panxian Dadong site in South China are dated to the late Middle Pleistocene (MIS 8e6 or ca. 130e300 ka), a period for which very little is known about the morphology of Asian populations. The present study provides the first detailed morphometric description and comparisons of four hominin teeth (I 1 , C 1 , P 3 and P 3) from this site. Our study shows that the Panxian Dadong teeth combine archaic and derived features that align them with Middle and Upper Pleistocene fossils from East and West Asia and Europe. These teeth do not display any typical Neanderthal features and they are generally more derived than other con-temporaneous populations from Asia and Africa. However, the derived traits are not diagnostic enough to specifically link the Panxian Dadong teeth to Homo sapiens, a common problem when analyzing the Middle Pleistocene dental record from Africa and Asia. These findings are contextualized in the dis-cussion of the evolutionary course of Asian Middle Pleistocene hominins, and they highlight the ne-cessity of incorporating the Asian fossil record in the still open debate about the origin of H. sapiens.
    Journal of Human Evolution 05/2013; 64(5):337-355. DOI:10.1016/j.jhevol.2012.10.012 · 3.73 Impact Factor
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    • "This hypothesis can be ruled out, however, in light of the aforementioned higher frequencies of molar reduction reported in other studies of dental characters (Bailey, 2002; Martinón-Torres, 2006), which are eventually driving the general morphologies described through geometric morphometric methods. The highly derived morphology observed in the European Middle Pleistocene sample can also be a populational characteristic of the SH sample (Gómez-Robles et al., 2008, 2011b) that perhaps cannot be extrapolated to other Middle Pleistocene specimens (Bailey, 2002; Bermúdez de Castro et al., 2003; Martinón-Torres, 2006). The more primitive morphologies of the Mauer or Arago fossils has led Tattersall (2007) to propose the coexistence of two different groups of hominins in Europe during the Middle Pleistocene: one including SH and the Steinheim fossils (which would eventually give rise to classic Neanderthals), and a geographically wider spread lineage including specimens such as those from Arago, Mauer and Petralona in Europe, Bodo and Kabwe in Africa, and, perhaps, Dali and Jinniushan in Asia. "
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    ABSTRACT: The study of dental morphology by means of geometric morphometric methods allows for a detailed and quantitative comparison of hominin species that is useful for taxonomic assignment and phylogenetic reconstruction. Upper second and third molars have been studied in a comprehensive sample of Plio- and Pleistocene hominins from African, Asian and European sites in order to complete our analysis of the upper postcanine dentition. Intraspecific variation in these two molars is high, but some interspecific trends can be identified. Both molars exhibit a strong reduction of the distal cusps in recent hominin species, namely European Homo heidelbergensis, Homo neanderthalensis and Homo sapiens, but this reduction shows specific patterns and proportions in the three groups. Second molars tend to show four well developed cusps in earlier hominin species and their morphology is only marginally affected by allometric effects. Third molars can be incipiently reduced in earlier species and they evince a significant allometric component, identified both inter- and intraspecifically. European Middle Pleistocene fossils from Sima de los Huesos (SH) show a very strong reduction of these two molars, even more marked than the reduction observed in Neanderthals and in modern human populations. The highly derived shape of SH molars points to an early acquisition of typical Neanderthal dental traits by pre-Neanderthal populations and to a deviation of this population from mean morphologies of other European Middle Pleistocene groups.
    Journal of Human Evolution 07/2012; 63(3):512-26. DOI:10.1016/j.jhevol.2012.06.002 · 3.73 Impact Factor
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