Detection of sexual dimorphism in the human neurocranium at local scale

In physical anthropology sexual dimorphism refers to the morphological differences observed in female and male individuals belonging to the same species. In the human cranium a number of anatomical traits are known to be sexual dimorphic. In this work, we present a geometric morphometric approach to automatically detect the most sexual dimorphic on skeletal collections. We applied the workflow on the human neurocranium and we defined, without an a priori definition of modules, which portions are most sexually dimorphic. We used a large sample of sex-known human 3D skulls to analyse the rate of sexual dimorphism found in the human neurocranium. We applied the Procrustes ANOVA on the best dimorphic patch found using the proposed workflow. We calculated the accuracy in discriminating sex in a sex-known sample by using our proposed model and the traditional approach

Seeing the wood through the trees. Combining shape information from different landmark configurations

The geometric morphometric (GM) analysis of complex anatomical structures is an ever more powerful tool to study biological variability, adaptation and evolution. Here, we propose a new method (combinland), developed in R, meant to combine the morphological information contained in different landmark coordinate sets into a single dataset, under a GM context. combinland builds a common ordination space taking into account the entire shape information encoded in the starting configurations. We applied combinland to a Primate case study including 133 skulls belonging to 14 species. On each specimen, we simulated photo acquisitions converting the 3D landmark sets into six 2D configurations along standard anatomical views. The application of combinland shows statistically negligible differences in the ordination space compared to that of the original 3D objects, in contrast to a previous method meant to address the same issue. Hence, we argue combinland allows to correctly retrieve 3D-quality statistical information from 2D landmark configurations. This makes combinland a viable alternative when the extraction of 3D models is not possible, recommended, or too expensive, and to make full use of disparate sources (and views) of morphological information regarding the same specimens. The code and examples for the application of combinland are available in the Arothron R package

A computational re-assessment of sexual dimorphism in the human cranium beyond traditional morphometrics: geometric morphometric methods and neural network analysis

L'objectiu principal d'aquesta tesi de doctorat és avançar en l'estudi i la comprensió del dimorfisme sexual en els cranis humans moderns. Per aconseguir aquests objectius, primerament explorem quines són les característiques anatòmiques adequades per establir el dimorfisme sexual. En segon lloc, introduïm un mètode innovador per determinar el sexe dels cranis humans. Per complir aquests objectius, apliquem l'enfocament de Morfometria Geomètrica a una mostra geogràfica diversa de cranis. La nostra recerca abasta tres estudis diferents, un centrat en el neurocrani, un altre en l'os frontal i l'últim en el crani complet, amb un total de 228 individus, tant dones com homes. A la recerca del segon objectiu, realitzem un Neural Network Analysis utilitzant 10 mesures lineals. Emprarem un conjunt de dades global per a aquest anàlisi. Els resultats obtinguts d'aquests quatre estudis demostren la utilitat tant de la Morfometria Geomètrica com de la Neural Network Analysis en l'avanç de la nostra comprensió del dimorfisme sexual en els cranis humans.El objetivo principal de esta tesis de doctorado es avanzar en el estudio y la comprensión del dimorfismo sexual en los cráneos humanos modernos. Para lograr estos objetivos, primero exploramos cuáles son las características anatómicas adecuadas para establecer el dimorfismo sexual. En segundo lugar, introducimos un método novedoso para determinar el sexo de los cráneos humanos. Para cumplir con estos objetivos, aplicamos el enfoque de Morfometría Geométrica a una muestra de proveniencia geográficas variadas de cráneos. Nuestra investigación abarca tres estudios distintos, uno centrado en el neurocráneo, otro en el hueso frontal y el último en el cráneo completo, involucrando un total de 228 individuos, tanto mujeres como hombres. En busca del segundo objetivo, realizamos un Neural Network Analysis utilizando 10 mediciones lineales. Empleamos un conjunto de datos global para este análisis. Los resultados derivados de estos cuatro estudios demuestran la utilidad tanto de la Morfometría Geométrica como del Neural Network Analysis en el avance de nuestra comprensión del dimorfismo sexual en los cráneos humanos.The primary objective of this Ph.D. dissertation is to advance the study and understanding of sexual dimorphism in modern human crania. To achieve these objectives, we first explore which anatomical features are suitable for establishing sexual dimorphism. Secondly, we introduce a novel method for determining the sex of human crania. To fulfill these objectives, we apply the Geometric Morphometrics approach to a diverse geographical sample of crania. Our research encompasses three distinct studies, one focusing on the neurocranium, another on the frontal bone, and the final one on the entire cranium, involving a total of 228 individuals, both female and male. In pursuit of the second objective, we conduct a Neural Network Analysis using 10 linear measurements. We employ a craniometric worldwide dataset for this analysis

Sexual dimorphim in the human calvarium. A geometric morphometric approach

In human evolution the assessment of sex in fossil specimen is performed by transposing the information relative from extant species (e.g., Homo sapiens, Pan paniscus, Gorilla gorilla) to extinct ones. The cranium is considered a key component in establishing others types of biological information including age, state of health and provenience and is considered the second important skeletal structure for a determination of sex after the pelvis [1]. In this communication, we analysed the human calvarium in know-sex specimens to detect which anatomical traits are more sexual dimorphic. To reach the aim of this project, we collected digital models of 165 adult specimens and on each skull we acquired 50 landmark on the entire cranial morphology. The only use of landmarks does not allow to study some anatomical traits due to lack of anatomical point. For this reason, we opted to collect also a surface patch of 500 semi-landmarks. We performed the analysis in R environment by using the Morpho, Arothron and geomorph R packages [2]–[4]. After semi-landmark placing and sliding, we split the semi-landmark configuration into three sub-regions: the entire calvarium, the frontal bone and the supraorbital torus. On each sub-region, we perfomed the General Procrustes Analysis (GPA) and the rotated configurations were subjected to Procrustes Anova to calculate the relation between shape and sex. Subsequently, we calculated the shape variations associated to the female and male morphology. All the sub-regions resulted related to sex variable, the R-squared from Procrustes Anova are the following 0.014, 0.024 and 0.048 for calvaria, frontal bones and supraorbital torus respectively. The shape variation associated to female morphology highlights the presence of more vertical frontal bone, short brain case and more shortening part of posterior parietal bones. On the contrary the male morphology is characterized by more horizontal profile of frontal bone, larger brain case above all in posterior part of parietal bones. In sum a geometric morphometric approach applied on the study of sexual dimorphism resulted very useful in the determination of sex because the accuracy value are higher (82% for the entire calvarium, 85% for both frontal bone and supraorbital torus) than currently (i.e., traditional) methods used to establish sex in unknown sample. Future researc

A COMPARISON OF ENDOCRANIAL OCCIPITAL BONE MORPHOLOGY IN MODERN HUMAN AND FOSSIL HOMININS

The evolution of cranial morphology in the genus Homo has been characterized by a trend of encephalization [1]. The occipital bone is one of the most studied cranial regions to infer the taxonomic status of human fossil individuals. In fact, the evolution of the genus Homo has been characterized by a progressive increment of brain volume and external occipital morphology seems to record someway this trend. Beside the cranial capacity, the occipital bone shows specific diagnostic traits in different fossil human species like the robust torus in Homo erectus and the “occipital bun” combined to the presence of the supra-iniac fossa in Neanderthals [2]. In the last decades, thanks to the arisen of virtual anthropology, it has been possible to analyze by means of advanced morphometric methods also the endocranial morphology in fossil hominins. This communication aims to compare the endocranial occipital bone morphology in modern humans (N=31) and in fossil hominins (H. erectus, N=3; H. heidelbergensis, N=5; and H. neanderthalensis, N=4) by geometric morphometrics and to test the correlation between shape and brain volume in modern humans and fossil hominins. To acquire the endocranial morphology of the occipital bone we defined 13 fixed landmarks and a set of 40 bilateral surface semilandmarks. The configurations have been analyses via principal component analysis after performing the Procrustes registration. The plot of the first two principal components shows as modern humans occupy large part of the variability. Furthermore, Homo heidelbergensis fossil specimens are in between Homo erectus and Neanderthals along PC2. The 14.15% of the total variance is significantly linked to the taxonomic status and the correlation between endocranial morphology and brain volume is statistically significant only in modern humans (R 2 =0.19, p-value = 0.001). In conclusion our preliminary results show as the endocranial morphology of the occipital bone is different among different human species and there is not a significant correlation between brain volume and endocranial morphology

Mapping sexual dimorphism signal in the human cranium

Abstract The study of sexual dimorphism in human crania has important applications in the fields of human evolution and human osteology. Current, the identification of sex from cranial morphology relies on manual visual inspection of identifiable anatomical features, which can lead to bias due to user’s expertise. We developed a landmark-based approach to automatically map the sexual dimorphism signal on the human cranium. We used a sex-known sample of 228 individuals from different geographical locations to identify which cranial regions are most sexually dimorphic taking into account shape, form and size. Our results, which align with standard protocols, show that glabellar and supraciliary regions, the mastoid process and the nasal region are the most sexually dimorphic traits (with an accuracy of 73%). The accuracy increased to 77% if they were considered together. Surprisingly the occipital external protuberance resulted to be not sexually dimorphic but mainly related to variations in size. Our approach here applied could be expanded to map other variable signals on skeletal morphology

Digital Reconstructions Using Linear Regression: How Well Can It Estimate Missing Shape Data from Small Damaged Areas?

Skeletal remains analyzed by anthropologists, paleontologists and forensic scientists are usually found fragmented or incomplete. Accurate estimations of the original morphologies are a challenge for which several digital reconstruction methods have been proposed. In this study, the accuracy of reconstructing bones based on multiple linear regression (RM) was tested. A total of 150 digital models from complete zygomatics from recent past populations (European and African American) were studied using high-density geometric morphometrics. Some landmarks (i.e., 2, 3 and 6) were coded as missing to simulate incomplete zygomatics and the missing landmarks were estimated with RM. In the zygomatics, this simulated damage affects a few square centimeters or less. Finally, the predicted and original shape data were compared. The results indicate that the predicted landmark coordinates were significantly different from the original ones, although this difference was less than the difference between the original zygomatic and the mean zygomatic in the sample. The performance of the method was affected by the location and the number of missing landmarks, with decreasing accuracy with increasing damaged area. We conclude that RM can accurately estimate the original appearance of the zygomatics when the damage is small

A New Integrated Tool to Calculate and Map Bilateral Asymmetry on Three-Dimensional Digital Models

The observation and the quantification of asymmetry in biological structures are deeply investigated in geometric morphometrics. Patterns of asymmetry were explored in both living and fossil species. In living organisms, levels of directional and fluctuating asymmetry are informative about developmental processes and health status of the individuals. Paleontologists are primarily interested in asymmetric features introduced by the taphonomic process, as they may significantly alter the original shape of the biological remains, hampering the interpretation of morphological features which may have profound evolutionary significance. Here, we provide a new R tool that produces the numerical quantification of fluctuating and directional asymmetry and charts asymmetry directly on the specimens under study, allowing the visual inspection of the asymmetry pattern. We tested this show.asymmetry algorithm, written in the R language, on fossil and living cranial remains of the genus Homo. show.asymmetry proved successful in discriminating levels of asymmetry among sexes in Homo sapiens, to tell apart fossil from living Homo skulls, to map effectively taphonomic distortion directly on the fossil skulls, and to provide evidence that digital restoration obliterates natural asymmetry to unnaturally low levels

Grandir dans une communauté de l’âge du cuivre en Italie : le rôle des enfants dans la vie quotidienne

journées 2023 de la société d' anthropologie de ParisInternational audienceThe study of children’s role in past communities is difficult to face in archaeology. An active contribution of the children in everyday life varies within societies and cultures, as well as the social and biological definition of childhood. In Central Italy, specific funerary customs for subadults are documented in the Copper Age(4th-3rd millennia BCE) according to age classes. Here we propose to investigate childhood in an Italian Copper Age human group by a multi- isotope analysis (δ$^{13}$C, δ$^{15}$N,δ$^{34}$S and $^{87}$Sr/$^{86}$Sr) on dentine/enamel and bone of two adult individuals, from the funerary cave of Grotta Spinosa (Central Italy). The reconstruction of the dietary intake variation and of the displacements occurred during early-life was compared to the adult values and to those of the rest of the group analysed, as well as the few comparative data available from prehistoric Italy. The framework obtained from this multi-tissue and multi-isotope study helped to shed light on experiences previously only suggested by the archaeological and skeletal evidence (i.e. passage to adulthood, and children’s implication in community life). The interpretation of the isotopic data in the light of the archaeological and biological information available, from the cave and the region (Central Italy), allowed us to suggest an age interval (ca. 10-12 y.o.) in which the children were likely involved in the "adult’s" tasks. This exploratory study highlights the interest of geochemical tools applied on archaeological remains and the need to develop further high-resolution and multi-tissue sampling when investigating particular past population practices

A New Integrated Tool to Calculate and Map Bilateral Asymmetry on Three-Dimensional Digital Models

The observation and the quantification of asymmetry in biological structures are deeply investigated in geometric morphometrics. Patterns of asymmetry were explored in both living and fossil species. In living organisms, levels of directional and fluctuating asymmetry are informative about developmental processes and health status of the individuals. Paleontologists are primarily interested in asymmetric features introduced by the taphonomic process, as they may significantly alter the original shape of the biological remains, hampering the interpretation of morphological features which may have profound evolutionary significance. Here, we provide a new R tool that produces the numerical quantification of fluctuating and directional asymmetry and charts asymmetry directly on the specimens under study, allowing the visual inspection of the asymmetry pattern. We tested this show.asymmetry algorithm, written in the R language, on fossil and living cranial remains of the genus Homo. show.asymmetry proved successful in discriminating levels of asymmetry among sexes in Homo sapiens, to tell apart fossil from living Homo skulls, to map effectively taphonomic distortion directly on the fossil skulls, and to provide evidence that digital restoration obliterates natural asymmetry to unnaturally low levels