A geometric morphometric analysis of hominin upper first molar

Centro Nacional de Investigación sobre Evolución Humana (CENIEH), Avda. de la Paz, 28, 09006 Burgos, Spain.
Journal of Human Evolution (Impact Factor: 3.73). 10/2007; 53(3):272-85. DOI: 10.1016/j.jhevol.2007.02.002
Source: PubMed


Recent studies have revealed interesting differences in upper first molar morphology across the hominin fossil record, particularly significant between H. sapiens and H. neanderthalensis. Usually these analyses have been performed by means of classic morphometric methods, including the measurement of relative cusp areas or the angles defined between cusps. Although these studies have provided valuable information for the morphological characterization of some hominin species, we believe that the analysis of this particular tooth could be more conclusive for taxonomic assignment. In this study, we have applied geometric morphometric methods to explore the morphological variability of the upper first molar (M(1)) across the human fossil record. Our emphasis focuses on the study of the phenetic relationships among the European middle Pleistocene populations (designated as H. heidelbergensis) with H. neanderthalensis and H. sapiens, but the inclusion of Australopithecus and early Homo specimens has helped us to assess the polarity of the observed traits. H. neanderthalensis presents a unique morphology characterized by a relatively distal displacement of the lingual cusps and protrusion in the external outline of a large and bulging hypocone. This morphology can be found in a less pronounced degree in the European early and middle Pleistocene populations, and reaches its maximum expression with the H. neanderthalensis lineage. In contrast, modern humans retain the primitive morphology with a square occlusal polygon associated with a round external outline.


Available from: Aida Gomez-Robles
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    • "Detailed information on methods in GM can be found in numerous sources [Bookstein, 1989, 1991; Richtsmeier et al., 2002; Adams et al., 2004; Zelditch et al., 2004; Slice, 2007; Mitteroecker and Gunz, 2009]. The contribution of GM to phylogenetic studies depends on the correlation of shape variability with taxonomic affinities [Bailey, 2004; Macholán, 2006; Gómez-Robles et al., 2007; Astúa, 2009; White, 2009]. To date, most GM dental analyses of occlusal crown surfaces have focused on the Hominidae [Martinón-Torres et al., 2006; Gómez-Robles, 2007, 2008], and only a few have examined cercopithecoids . "
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    ABSTRACT: Morphometric variation of biological structures has been widely used to determine taxonomic affinities among taxa, and teeth are especially informative for both deep phylogenetic relationships and specific ecological signals. We report 2-dimensional geometric morphometrics (GM) analyses of occlusal crown surfaces of lower molars (M1, n = 141; M2, n = 158) of cercopithecoid primate species. A 12-landmark configuration, including cusp tips and 8 points of the molar crown contour, were used to evaluate patterns of variation in lower molar shape among cercopithecoid primates and to predict the taxonomic attribution of 2 archaeological macaques from Roman time periods. The results showed that the lower molar shape of cercopithecoid primates reflects taxonomic affinities, mostly at a subfamily level and close to a tribe level. Thus, the cusp positions and crown contour were important elements of the pattern related to interspecific variation. Additionally, the archaeological specimens, attributed to Macaca sylvanus based on osteological information, were classified using the GM molar shape variability of the cercopithecoid primates studied. The results suggest that their molar shape resembled both M. sylvanus and M. nemestrina, and species attribution varied depending on the comparative sample used.
    Folia Primatologica 02/2015; 2014(85):361-378. DOI:10.1159/000371633 · 0.89 Impact Factor
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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). GMM analyses the relative positions of anatomical landmarks used to approximate the outlines and surfaces of the tested object. "
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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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    • "However, these methods are less practical for quantifying tooth shape, as they require micro-CT data that are costly and time-consuming to collect, limiting the sampling potential. Two-dimensional morphometrics has been successfully used to examine occlusal morphology in hominins (G omez-Robles, 2008; Gomez-Robles et al., 2007), rodents (Macholan, 2006; Renaud, 1999), and primates (White, 2009), and has been found to provide more shape information than simple linear measures (Bernal, 2007). Twodimensional photographs of the lingual aspect of the tooth were deemed most appropriate for our analysis for several reasons: (1) the majority of shape variation in the taxa sampled occurs in this plane (roughly parasagittal); (2) the lateral aspect of the tooth is relatively flat, thus allowing repeatable positioning of the tooth for imaging; and (3) several homologous landmarks were identifiable on the lingual surfaces of these teeth. "
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    ABSTRACT: The earliest euprimates to arrive in North America were larger-bodied notharctids and smaller-bodied omomyids. Through the Eocene, notharctids generally continued to increase in body size, whereas omomyids generally radiated within small- and increasingly mid-sized niches in the middle Eocene. This study examines the influence of changing body size and diet on the evolution of the lower fourth premolar in Eocene euprimates. The P4 displays considerable morphological variability in these taxa. Despite the fact that most studies of primate dental morphology have focused on the molars, P4 can also provide important paleoecological insights. We analyzed the P4 from 177 euprimate specimens, representing 35 species (11 notharctids and 24 omomyids), in three time bins of approximately equal duration: early Wasatchian, late Wasatchian, and Bridgerian. Two-dimensional surface landmarks were collected from lingual photographs, capturing important variation in cusp position and tooth shape. Disparity metrics were calculated and compared for the three time bins. In the early Eocene, notharctids have a more molarized P4 than omomyids. During the Bridgerian, expanding body size range of omomyids was accompanied by a significant increase in P4 disparity and convergent evolution of the semimolariform condition in the largest omomyines. P4 morphology relates to diet in early euprimates, although patterns vary between families. Am J Phys Anthropol 153:15-28, 2014. © 2013 Wiley Periodicals, Inc.
    American Journal of Physical Anthropology 01/2014; 153(1):15-28. DOI:10.1002/ajpa.22387 · 2.38 Impact Factor
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