Variation of mandibular sexual dimorphism across human facial patterns

Received 2 March 2015Accepted 1 November 2015 Available online 23 January 2016This study analysed how sex-specific features differed in male and female adult mandibles throughout the spectrum of vertical facial patterns (i.e., meso-, dolicho- and brachyfacial) and sagittal variations (the so-called skeletal Classes I, II and III; normal maxillo-mandibular relationship, maxillary prognathism vs. mandibular retrognathism, and maxillary retrognathism vs. mandibular prognathism, respectively). Specifically, we test the hypothesis that sexual dimorphism in the mandible is independent of such facial vertical and sagittal patterns. A sample of 187 European adults (92 males, 95 females; age range, 20–30 years; mean age 25.6 years, sd = 4.2 years) from Granada (southern Spain) were randomly selected and grouped according to the standard cephalometric criteria of the sagittal and vertical patterns. Geometric morphometrics were used to analyse the size (centroid size) and shape (principal components analysis, mean shape comparisons) of the mandible. The patterns of sexual dimorphism were evaluated with a generalised linear model with interaction term. We found that sagittal and vertical facial patterns are associated with different mandibular morphologies (size and shape). Also, sexual dimorphism was present in all comparisons. The hypothesis was rejected only for vertical facial patterns. That is, the nature of sexual dimorphism was similar among the skeletal classes but different (e.g., distribution of dimorphic variables, interaction term) in meso-, dolicho-, and brachyfacial mandibles. In conclusion, sex-specific mandibular traits behave in a different way across vertical facial patterns. These results imply that an assessment of the vertical facial pattern of the individual is required before a sexual diagnosis of the mandible is proposed.This research was funded by the Spanish Ministry of Economy andCompetitiveness: Projects CGL2012-36682 and CGL2012-37279.Peer reviewe

Middle Cranial Fossa Anatomy and the Origin of Modern Humans

Anatomically, modern humans differ from archaic forms in possessing a globular neurocranium and a retracted face and in cognitive functions, many of which are associated with the temporal lobes. The middle cranial fossa (MCF) interacts during growth and development with the temporal lobes, the midface, and the mandible. It has been proposed that evolutionary transformations of the MCF (perhaps from modification of the temporal lobes) can have substantial influences on craniofacial morphology. Here, we use three-dimensional (3D) geometric morphometrics and computer reconstructions of computed tomography-scanned fossil hominids, fossil and recent modern humans and chimpanzees to address this issue further. Mean comparisons and permutation analyses of scaled 3D basicranial landmarks confirm that the MCF of Homo sapiens is highly significantly different (P < 0.001) from H. neanderthalensis, H. heidelbergensis, and Pan troglodytes. Modern humans have a unique configuration with relatively more anterolateral projection of the MCF pole relative to the optic chiasm and the foramen rotundum. These findings are discussed in the context of evolutionary changes in craniofacial morphology and the origins of modern human autapomorphies. In particular, the findings of this study point to variations in the temporal lobe, which, through effects on the MCF and face, are central to the evolution of modern human facial form.Anthropolog

Geometric morphometrics of rodent sperm head shape

Mammalian spermatozoa, particularly those of rodent species, are extremely complex cells and differ greatly in form and dimensions. Thus, characterization of sperm size and, particularly, sperm shape represents a major challenge. No consensus exists on a method to objectively assess size and shape of spermatozoa. In this study we apply the principles of geometric morphometrics to analyze rodent sperm head morphology and compare them with two traditional morphometry methods, that is, measurements of linear dimensions and dimensions-derived parameters calculated using formulae employed in sperm morphometry assessments. Our results show that geometric morphometrics clearly identifies shape differences among rodent spermatozoa. It is also capable of discriminating between size and shape and to analyze these two variables separately. Thus, it provides an accurate method to assess sperm head shape. Furthermore, it can identify which sperm morphology traits differ between species, such as the protrusion or retraction of the base of the head, the orientation and relative position of the site of flagellum insertion, the degree of curvature of the hook, and other distinct anatomical features and appendices. We envisage that the use of geometric morphometrics may have a major impact on future studies focused on the characterization of sperm head formation, diversity of sperm head shape among species (and underlying evolutionary forces), the effects of reprotoxicants on changes in cell shape, and phenotyping of genetically-modified individuals. © 2013 Varea Sánchez et al.This work was supported by the Spanish Ministry of Economy and Competitiveness.Peer Reviewe

Morphological integration of mandible and cranium: Orthodontic implications

Objectives: This study aimed at clarifying the morphological interactions among the cranial base, face, and mandible, to improve the assessment and treatment of skeletal malocclusions involving the mandible. Design Untreated adult subjects (n = 187) were grouped according to standard cephalometric criteria of vertical and sagittal relationships. Geometric morphometrics were used to test the null hypothesis that integration patterns between the mandible and its associated basicranial and upper midfacial counterparts would be similar among various vertical and sagittal facial patterns. Results: The null hypothesis was rejected for vertical groups, because the dolicho- and brachyfacial subjects showed significantly different integration patterns, but was accepted for sagittal groups, which showed identical covariation patterns. The morphological integration between the cranium-face and mandible were similarly high in the three skeletal classes, which explained the similarly large covariance between the two structures (57.80% in Class II to 60% in Class III). Conclusions: Dolicho- and brachi-facial subjects showed specific and different cranium-face and associated mandible configurations. The cranium-face configuration may have an important influence (∼60%) on the generation of sagittal (anteroposterior) skeletal malocclusions. The remaining morphological component of the skeletal malocclusion (∼40%) would be independent of this particular integration (PLS1) between the cranium-face and mandible. © 2013 Elsevier Ltd.This research was founded by the Spanish Ministry of Economy and Competitiveness (Projects CGL2012-36682 and CGL2012-37279).Peer Reviewe

Temporal lobe surface anatomy and the bony relieves in the middle cranial fossa. The case of the El Sidrón (Spain) Neandertal sample

Resumen del póster presentado en: 3rd Annual Meeting of the European Society for the study of Human Evolution, 19-21 September 2013, Vienna/AustriaCGL 2012-36682 and CGL 2012-37279 (MINECO, Spain). Field work is supported by Consejería de Cultura del Principado de Asturias, Grant sponsor: Convenio Universidad de Oviedo-CSIC, Grant number: 060501040023Peer reviewe

Investigating Human Torso Asymmetries: An Observational Longitudinal Study of Fluctuating and Directional Asymmetry in the Scoliotic Torso

The presence of directional and fluctuating asymmetry in adolescent idiopathic scoliosis has not been deeply studied. We aimed to test the presence of both in a scoliosis group and a control group. 24 patients with adolescent idiopathic scoliosis and 24 control subjects were subjected to geometric morphometrics analyses to address our main hypotheses and to make qualitative visualizations of the 3D shape changes in patients with scoliosis. Our results support the hypothesis that both asymmetric traits are present in the scoliosis and control groups, but to a greater degree in patients. A qualitative visualization tool that allows us to measure the impact that directional and fluctuating asymmetry have on the 3D shape of our patients has been developed. Adolescent idiopathic scoliosis is the result of developmental instabilities during growth and the visualization of the 3D shape changes in response to both asymmetric variables has shown different morphological behaviors. Measuring these variables is important, as they can prevent the localization and deformation that is expected to occur during the course of scoliosis in every individual patient and therefore acts as a key clinical finding that may be used in the prognosis of the condition.Funding: This research was funded by the Spanish Ministry of Science and Innovation, grant number PID2020-115854GB-I00 and the APC was funded by the Spanish Ministry of Science and Innovation, grant number PID2020-115854GB-I00

Fetal development of the modern human chin: The 3D shape variation is bounded to spatial arrangement of the hyoid bone, the tongue and suprahyoid muscles

Resumen del póster presentado en: 3rd Annual Meeting of the European Society for the study of Human Evolution, 19-21 September 2013, Vienna/AustriaPeer reviewe

Genetic evidence for patrilocal mating behaviour among Neandertal groups

The remains of 12 Neandertal individuals have been found at the El Sidrón site (Asturias, Spain), consisting of six adults, three adolescents, two juveniles, and one infant. Archaeological, paleontological, and geological evidence indicates that these individuals represent all or part of a contemporaneous social group of Neandertals, who died at around the same time and later were buried together as a result of a collapse of an underground karst. We sequenced phylogenetically informative positions of mtDNA hypervariable regions 1 and 2 from each of the remains. Our results show that the 12 individuals stem from three different maternal lineages, accounting for seven, four, and one individual(s), respectively. Using a Y-chromosome assay to confirm the morphological determination of sex for each individual, we found that, although the three adult males carried the same mtDNA lineage, each of the three adult females carried different mtDNA lineages. These findings provide evidence to indicate that Neandertal groups not only were small and characterized by low genetic diversity but also were likely to have practiced patrilocal mating behavior.C.L.-F. also is supported by an Intramural Grant from the Consejo Superior de Investigaciones Cientificas. A.R., A.E., M.B., A.G.-T., and S.G.-V. are supported by Grant CGL2009-09013 from the Ministry of Science and Innovation of Spain.Peer reviewe

Evolution of the base of the brain in highly encephalized human species

The increase of brain size relative to body size-encephalization-is intimately linked with human evolution. However, two genetically different evolutionary lineages, Neanderthals and modern humans, have produced similarly large-brained human species. Thus, understanding human brain evolution should include research into specific cerebral reorganization, possibly reflected by brain shape changes. Here we exploit developmental integration between the brain and its underlying skeletal base to test hypotheses about brain evolution in Homo. Three-dimensional geometric morphometric analyses of endobasicranial shape reveal previously undocumented details of evolutionary changes in Homo sapiens. Larger olfactory bulbs, relatively wider orbitofrontal cortex, relatively increased and forward projecting temporal lobe poles appear unique to modern humans. Such brain reorganization, beside physical consequences for overall skull shape, might have contributed to the evolution of H. sapiens' learning and social capacities, in which higher olfactory functions and its cognitive, neurological behavioral implications could have been hitherto underestimated factors. © 2011 Macmillan Publishers Limited. All rights reserved.Peer Reviewe

A preliminary assessment of the thoracic remains of the El Sidrón Neandertals (Asturias, Spain)

Resumen del póster presentado en: 3rd Annual Meeting of the European Society for the study of Human Evolution, 19-21 September 2013, Vienna/AustriaPeer reviewe