Quantitative analysis of human mandibular shape using three-dimensional geometric morphometrics

Shape variation and sex differences of the adult human mandible evaluated by geometric morphometrics

In cases of osseous defects, knowledge of the anatomy, and its age and sex-related variations, is essential for reconstruction of normal morphology. Here, we aimed at creating a 3D atlas of the human mandible in an adult sample using dense landmarking and geometric morphometrics. We segmented 50 male and 50 female mandibular surfaces from CBCT images (age range: 18.9-73.7 years). Nine fixed landmarks and 510 sliding semilandmarks were digitized on the mandibular surface, and then slid by minimizing bending energy against the average shape. Principal component analysis extracted the main patterns of shape variation. Sexes were compared with permutation tests and allometry was assessed by regressing on the log of the centroid size. Almost 49 percent of shape variation was described by the first three principal components. Shape variation was related to width, height and length proportions, variation of the angle between ramus and corpus, height of the coronoid process and inclination of the symphysis. Significant sex differences were detected, both in size and shape. Males were larger than females, had a higher ramus, more pronounced gonial angle, larger inter-gonial width, and more distinct antegonial notch. Accuracy of sexing based on the first two principal components in form space was 91 percent. The degree of edentulism was weakly related to mandibular shape. Age effects were not significant. The resulting atlas provides a dense description of mandibular form that can be used clinically as a guide for planning surgical reconstruction.

Finite element analysis of Neanderthal and early Homo sapiens maxillary central incisor

Neanderthal anterior teeth are very large and have a distinctive morphology characterized by robust 'shovel-shaped' crowns. These features are frequently seen as adaptive responses in dissipating heavy mechanical loads resulting from masticatory and non-masticatory activities. Although the long-standing debate surrounding this hypothesis has played a central role in paleoanthropology, is still unclear if Neanderthal anterior teeth can resist high mechanical loads or not. A novel way to answer this question is to use a multidisciplinary approach that considers together tooth architecture, dental wear and jaw movements. The aim of this study is to functionally reposition the teeth of Le Moustier 1 (a Neanderthal adolescent) and Qafzeh 9 (an early Homo sapiens adolescent) derived from wear facet mapping, occlusal fingerprint analysis and physical dental restoration methods. The restored dental arches are then used to perform finite element analysis on the left central maxillary incisor during edge-to-edge occlusion. The results show stress distribution differences between Le Moustier 1 and Qafzeh 9, with the former displaying higher tensile stress in enamel around the lingual fossa but lower concentration of stress in the lingual aspect of the root surface. These results seem to suggest that the presence of labial convexity, lingual tubercle and of a large root surface in Le Moustier 1 incisor helps in dissipating mechanical stress. The absence of these dental features in Qafzeh 9 is compensated by the presence of a thicker enamel, which helps in reducing the stress in the tooth crown.

Size and shape of human mandible: Sex differences and influence of age on sex estimation accuracy

The degree of sexual dimorphism expressed by human bones is of primary importance for the development of accurate methods for sex estimation. The objective of the present study was to investigate sex differences in shape and size of the mandible using geometric morphometric methods. The study also aimed to examine the impact of age on the sex classification ability of the size and shape of the mandible. Computed tomography images of 190 Bulgarians (98 males and 92 females) were used in the study. Polygonal surface models of the skulls were generated and used for digitizing 45 landmarks located on the mandible. The raw three-dimensional coordinates of the landmarks were processed via generalized Procrustes superimposition. The sex differences in mandibular size and shape were evaluated for statistical significance. Multivariate regression was applied for correction of the allometric effect. Principal component analysis, discriminant analysis, and canonical variate analysis were also used in the study. Mandibular size differed significantly between males and females and achieved a sex classification accuracy of 87%. The significance of the sex differences in mandibular shape depended on the type of shape variables used in the analysis. The shape variables provided different classification accuracy: 78% using the Procrustes coordinates and 53% using the regression residuals. The male and female mandibles differed significantly in size and shape, including the allometric component. Mandibular size is a more effective sex indicator than shape. Age has an ambiguous effect on the classification accuracy of the size and shape variables of the mandible.

Evaluation of sex dimorphism of the mandible with geometric morphometric analysis: conventional and reconstructed panoramic radiography study

PURPOSE

The purpose of the study was to investigate the mandible shape dimorphism between males and females both on conventional panoramic radiographs (cPR) and reconstructed panoramic radiographs obtained from cone beam computed tomography (rPR) with geometric morphometric method.

METHODS

Panoramic radiographs and cone beam computed tomography scans were performed on 33 males and 35 females with median age 23.0 (13.0-57.0) years old. The mandibular shape comparisons between genders were examined with Procrustes analysis, mandible shape classification analysis was made with principal component analysis and shape deformations were concluded from thin plate spline (TPS) analysis.

RESULTS

Age had no statistically significant difference between gender (p = 0.580). For the shape of mandible on cPR and rPR, there were statistically significant differences between males and females (p = 0.002, p = 0.032, respectively). The shape variabilities of mandible on cPR for females were 0.054 and for males 0.053. The shape variabilities of mandible on rPR for females were 0.051 and for males 0.049. Both on cPR and rPR, the shape variability of the females' mandible was similar within their group, the shape variability of the males' mandible was similar within their group. In the examination of mandibular dimorphism in cPR, maximal deformations were seen in the region between the mandibular notch, posterior ramus, anterior ramus, gonion, in both sides, in TPS graphs. On the other hand, a high level of deformations was observed in all landmarks that define the mandibular shape on rPR.

CONCLUSIONS

The mandible dimorphism can be detected in the examination performed with geometric morphometric methods on cPR and rPR. While mandible shape differences according to gender are seen most in the ramus region in cPR, differences can be detected in all landmarks in rRP.

Comparison of Six Different Methods for Measuring the Equine Hoof and Recording of its Three-Dimensional Conformation

Different measuring techniques have been used to objectify the classification of hoof shape. The MicroScribe is a novel tool that might prove useful for measuring hooves without prior reconstruction or compensation of projection artefacts. The aim of this study was to compare biometric data of the equine hoof collected by the MicroScribe tool and measurements collected directly from hooves, scaled photographs and radiographs, from photogrammetry models and computed tomography datasets. The suitability of MicroScribe generated data to differentiate individual hoof conformations was tested. A total of 62 measures were recorded from 16 forehooves. 21 linear and nine angular measures were collected by at least four methods each, and evaluated further by analysis of variance (ANOVA) and multivariate analysis of variance (MANOVA). Ratios and differences of these measures were calculated as suitable for the definition of hoof shapes and analysed as well. Absolute equivalency of methods was detected for five linear and none of the angular measurements. The precision of the tested measurement methods was comparable. In some cases, different methods measure different structures. Radiographs tended to overestimate, while computed tomography slides to underestimate distances. Photogrammetry and scaled photographs were less suitable for measuring hoof angles. The MicroScribe tool can readily be used for hoof measurements. Its values for linear measures showed good equivalency with other methods based on real hooves. For angular measurements, the uneven hoof surface might introduce imprecision. Not all hoof conformations could be detected based on measuring results alone. Diagnosis by a skilled veterinarian is still essential.

Reassessment of the human mandible from Banyoles (Girona, Spain)

Since the discovery of a human mandible in 1887 near the present-day city of Banyoles, northeastern Spain, researchers have generally emphasized its archaic features, including the lack of chin structures, and suggested affinities with the Neandertals or European Middle Pleistocene (Chibanian) specimens. Uranium-series and electron spin resonance dating suggest the mandible dates to the Late Pleistocene (Tarantian), approximately ca. 45-66 ka. In this study, we reassessed the taxonomic affinities of the Banyoles mandible by comparing it to samples of Middle Pleistocene fossils from Africa and Europe, Neandertals, Early and Upper Paleolithic modern humans, and recent modern humans. We evaluated the frequencies and expressions of morphological features and performed a three-dimensional geometric morphometric analysis on a virtual reconstruction of Banyoles to capture overall mandibular shape. Our results revealed no derived Neandertal morphological features in Banyoles. While a principal component analysis based on Euclidean distances from the first two principal components clearly grouped Banyoles with both fossil and recent Homo sapiens individuals, an analysis of the Procrustes residuals demonstrated that Banyoles did not fit into any of the comparative groups. The lack of Neandertal features in Banyoles is surprising considering its Late Pleistocene age. A consideration of the Middle Pleistocene fossil record in Europe and southwest Asia suggests that Banyoles is unlikely to represent a late-surviving Middle Pleistocene population. The lack of chin structures also complicates an assignment to H. sapiens, although early fossil H. sapiens do show somewhat variable development of the chin structures. Thus, Banyoles represents a non-Neandertal Late Pleistocene European individual and highlights the continuing signal of diversity in the hominin fossil record. The present situation makes Banyoles a prime candidate for ancient DNA or proteomic analyses, which may shed additional light on its taxonomic affinities.

Testing different 3D techniques using geometric morphometrics: Implications for cranial fluctuating asymmetry in humans

This study aimed to test the performance of 3D digitizer, CT scanner, and surface scanner in detecting cranial fluctuating asymmetry. Sets of 32 landmarks (6 in the midline and 13 bilateral) were acquired from 14 archeological crania using a 3D digitizer, and from 3D models generated from a CT scanner and surface scanner using Viewbox 4. Levels of shape variation were analyzed in MorphoJ using Procrustes analysis of variance and Principal component analysis. Intra-observer error accounted for 1.7%, 1.8%, and 4.5% of total shape variation for 3D digitizer, CT scanner, and surface scanner respectively. Fluctuating asymmetry accounted for 15%-16% of total shape variation. Variation between techniques accounted for 18% of total shape variation. We found a higher level of missing landmarks in our surface scan data than for both 3D digitizer and CT scanner data, and both 3D model-based techniques sometimes obscured taphonomic damage. All three 3D techniques are appropriate for measuring cranial fluctuating asymmetry. We advise against combining data collected with different techniques.

Merging morphological and genetic evidence to assess hybridization in Western Eurasian late Pleistocene hominins

Previous scientific consensus saw human evolution as defined by adaptive differences (behavioural and/or biological) and the emergence of Homo sapiens as the ultimate replacement of non-modern groups by a modern, adaptively more competitive group. However, recent research has shown that the process underlying our origins was considerably more complex. While archaeological and fossil evidence suggests that behavioural complexity may not be confined to the modern human lineage, recent palaeogenomic work shows that gene flow between distinct lineages (for example, Neanderthals, Denisovans, early H. sapiens) occurred repeatedly in the late Pleistocene, probably contributing elements to our genetic make-up that might have been crucial to our success as a diverse, adaptable species. Following these advances, the prevailing human origins model has shifted from one of near-complete replacement to a more nuanced view of partial replacement with considerable reticulation. Here we provide a brief introduction to the current genetic evidence for hybridization among hominins, its prevalence in, and effects on, comparative mammal groups, and especially how it manifests in the skull. We then explore the degree to which cranial variation seen in the fossil record of late Pleistocene hominins from Western Eurasia corresponds with our current genetic and comparative data. We are especially interested in understanding the degree to which skeletal data can reflect admixture. Our findings indicate some correspondence between these different lines of evidence, flag individual fossils as possibly admixed, and suggest that different cranial regions may preserve hybridization signals differentially. We urge further studies of the phenotype to expand our ability to detect the ways in which migration, interaction and genetic exchange have shaped the human past, beyond what is currently visible with the lens of ancient DNA.

A systematic review of treatment and outcomes in patients with mandibular coronoid process hyperplasia

Treatment of mandibular coronoid process hyperplasia (MCPH) has been described and explored in the literature. This systematic review aims to provide a comprehensive overview of the surgical and non-surgical treatment options for MCPH in pediatric and adult populations. Three databases were searched for treatment of MCPH patients (MEDLINE, Embase, and Web of Science). Two reviewers selected case reports and case series based on titles and abstracts. Finally, 55 studies reporting a total of 127 cases were included for qualitative synthesis and data extraction. The mean age at symptom onset was 15.6 years, while the mean age at diagnosis was 23.5 years. Of the included cases, 83.7% were male, and the condition was bilateral in more than 81% of the cases. Coronoidectomy was performed in 82.7% of the included cases, while coronoidotomy was performed in 3.9% of the cases. In 85.0% of the surgically treated cases, the approach was intraoral. The mean maximal intraoperative mouth opening was 38.1 mm compared with 16.5 mm at diagnosis. The mean maximal postoperative mouth opening was 35.3 mm, and the mean follow-up period was 16.3 months. Maximum mouth opening was achieved intraoperatively, and non-surgical treatment after surgery aims to reduce the risk of relapse. Additional research with a higher level of evidence is necessary to confirm these findings.

3D geometric morphometrics analysis of mandibular fragments of Ouranopithecus macedoniensis from the late Miocene deposits of Central Macedonia, Greece

OBJECTIVES

To explore mandibular shape differences between Ouranopithecus macedoniensis and a comparative sample of extant great apes using three-dimensional (3D) geometrics morphometrics. Other objectives are to assess mandibular shape variation and homogeneity within Ouranopithecus, explore the effects of size on mandibular shape, and explore the degree of mandibular sexual size dimorphism in Ouranopithecus.

MATERIALS AND METHODS

The comparative sample comprises digitized mandibles from adult extant great apes. The 3D analysis includes three datasets: one with landmarks registered on the mandibular corpus and symphysis of mandibles preserving both sides, one on hemimandibles only, and one focused on the ramus and gonial area. Multivariate statistical analyses were conducted, such as ordination analyses (PCA), intra-specific Procrustes distances pairs, pairwise male-female centroid size differences, and correlation analyses.

RESULTS

The male and female specimens of Ouranopithecus have mandibular shapes that are quite similar, although differences exist. The Procrustes distances results suggest more shape variation in Ouranopithecus than in the extant great apes. Ouranopithecus shows some similarities in mandibular shape to the larger great apes, Gorilla and Pongo. Moreover, the degree of sexual dimorphism in the small Ouranopithecus sample is greater than any of the great apes. Based on our correlation analyses of principal components (PC) with size, some PCs are significantly correlated with size, with correlation varying from moderate to substantial.

DISCUSSION

This study attempted to understand better the variation within the mandibles of O. macedoniensis and the expression of sexual dimorphism in this taxon in more detail than has been done previously. The overall mandibular morphology of Ouranopithecus shows some similarities to those of the larger great apes, which likely reflects similarities in size. Compared to Gorilla and Pongo, O. macedoniensis shows an elevated degree of morphological variation, although limitations relating to sample size apply. Sexual dimorphism in the mandibles of O. macedoniensis appears to be relatively high, seemingly greater than in Gorilla and high even in comparison to Pongo, but this again is possibly in part an artifact of a small sample size.

Sex and age biological variation of the mandible in a Portuguese population- a forensic and medico-legal approaches with three-dimensional analysis

The medico-legal identification is based on a set of discriminatory characteristics between individuals in their biological, social, cultural, religious, legal and economic framework. The purpose of this study was to characterize the biological variation, regarding gender and age, in a Portuguese population. A three-dimensional (3D) analysis of 215 mandibles (7-20 years old) from the database of the Laboratory of Forensic Dentistry, Faculty of Medicine, University of Coimbra (CE-112/2019) was performed. A total of 13 cephalometric points defined 10 linear variables and 7 angular variables, on 3D reconstructions from ConeBeam Computed Tomography (CBCT) images. Intra and inter-observer errors were analyzed by Technical Measurement Error test. A descriptive statistics was performed. To verify the influence of gender and age on the variables and to determine its predictive value, ANOVA and Logistic Regression Analysis were performed. Gender and age influence most of the linear variables, however, the same is not true for angular variables. In the analysis of all variables, the model has a reasonable level of sensitivity (67.8%) according to gender. For the age prediction, with all variables, the model presented a reasonable level of sensitivity, classifying 79.4% of the individuals. The results supported, with a high level of statistical significance, an adequate recognition of individuals highlighting the identification and criminal imputability of Portuguese individuals.

How did modern morphology evolve in the human mandible? The relationship between static adult allometry and mandibular variability in Homo sapiens

Key to understanding human origins are early Homo sapiens fossils from Jebel Irhoud, as well as from the early Late Pleistocene sites Tabun, Border Cave, Klasies River Mouth, Skhul, and Qafzeh. While their upper facial shape falls within the recent human range of variation, their mandibles display a mosaic morphology. Here we quantify how mandibular shape covaries with mandible size and how static allometry differs between Neanderthals, early H. sapiens, and modern humans from the Upper Paleolithic/Later Stone Age and Holocene (= later H. sapiens). We use 3D (semi)landmark geometric morphometric methods to visualize allometric trends and to explore how gracilization affects the expression of diagnostic shape features. Early H. sapiens were highly variable in mandible size, exhibiting a unique allometric trajectory that explains aspects of their 'archaic' appearance. At the same time, early H. sapiens share a suite of diagnostic features with later H. sapiens that are not related to mandibular sizes, such as an incipient chin and an anteroposteriorly decreasing corpus height. The mandibular morphology, often referred to as 'modern', can partly be explained by gracilization owing to size reduction. Despite distinct static allometric shape changes in each group studied, bicondylar and bigonial breadth represent important structural constraints for the expression of shape features in most Middle to Late Pleistocene hominin mandibles.

Sexual dimorphism of the mandibular conformational changes in aging human adults: A multislice computed tomographic study by geometric morphometrics

The aging process has an impact on mandibular bone morphology and can therefore affect shape sexual dimorphism. Understanding the effect of senescence on mandibular shape changes is particularly important to correctly estimate the sex of an individual and predict age-related conformational modifications. The purpose of this study was to assess age-related changes in mandibular shape and sexual dimorphism. The study sample comprised 160 Multi Slice Computed Tomography examinations of individuals aged 40 to 79 years. Geometric morphometric analysis of fourteen osteometric landmarks was used to examine sexual dimorphism and patterns of mandibular shape variation with age. Results showed that mandibular sexual dimorphism of shape remained significant with aging. Conformational changes occurred between 50 and 70 years and were different for male and female individuals. Females presented earlier and more marked age-related shape changes than males. These observations suggest that mandibular senescence is a sexually dimorphic process since its onset, rate, and the areas subjected to conformational changes differ from male to female individuals. Senescence-related changes present substantial variability, and further investigation is required to determine precisely the age that marks their onset.

Ontogenetic changes in magnitudes of integration in the macaque skull

OBJECTIVES

Magnitudes of morphological integration may constrain or facilitate craniofacial shape variation. The aim of this study was to analyze how the magnitude of integration in the skull of Macaca fascicularis changes throughout ontogeny in relation to developmental and/or functional modules.

MATERIALS AND METHODS

Geometric morphometric methods were used to analyze the magnitude of integration in the macaque cranium and mandible in 80 juvenile and 40 adult M. fascicularis specimens. Integration scores in skull modules were calculated using integration coefficient of variation (ICV) of eigenvalues based on a resampling procedure. Resultant ICV scores between the skull as a whole, and developmental and/or functional modules were compared using Mann-Whitney U tests.

RESULTS

Results showed that most skull modules were more tightly integrated than the skull as a whole, with the exception of the chondrocranium in juveniles without canines, the chondrocranium/face complex and the mandibular corpus in adults, and the mandibular ramus in all juveniles. The chondrocranium/face and face/mandibular corpus complexes were more tightly integrated in juveniles than adults, possibly reflecting the influences of early brain growth/development, and the changing functional demands of infant suckling and later masticatory loading. This is also supported by the much higher integration of the mandibular ramus in adults compared with juveniles.

DISCUSSION

Magnitudes of integration in skull modules reflect developmental/functional mechanisms in M. fascicularis. However, the relationship between "evolutionary flexibility" and developmental/functional mechanisms was not direct or simple, likely because of the complex morphology, multifunctionality, and various ossification origins of the skull.

Are geometric morphometric analyses replicable? Evaluating landmark measurement error and its impact on extant and fossil Microtus classification

Geometric morphometric analyses are frequently employed to quantify biological shape and shape variation. Despite the popularity of this technique, quantification of measurement error in geometric morphometric datasets and its impact on statistical results is seldom assessed in the literature. Here, we evaluate error on 2D landmark coordinate configurations of the lower first molar of five North American Microtus (vole) species. We acquired data from the same specimens several times to quantify error from four data acquisition sources: specimen presentation, imaging devices, interobserver variation, and intraobserver variation. We then evaluated the impact of those errors on linear discriminant analysis-based classifications of the five species using recent specimens of known species affinity and fossil specimens of unknown species affinity. Results indicate that data acquisition error can be substantial, sometimes explaining >30% of the total variation among datasets. Comparisons of datasets digitized by different individuals exhibit the greatest discrepancies in landmark precision, and comparison of datasets photographed from different presentation angles yields the greatest discrepancies in species classification results. All error sources impact statistical classification to some extent. For example, no two landmark dataset replicates exhibit the same predicted group memberships of recent or fossil specimens. Our findings emphasize the need to mitigate error as much as possible during geometric morphometric data collection. Though the impact of measurement error on statistical fidelity is likely analysis-specific, we recommend that all geometric morphometric studies standardize specimen imaging equipment, specimen presentations (if analyses are 2D), and landmark digitizers to reduce error and subsequent analytical misinterpretations.

Morphological consequences of artificial cranial deformation: Modularity and integration

The cranium is an anatomically complex structure. One source of its complexity is due to its modular organization. Cranial modules are distinct and partially independent units that interact substantially during ontogeny thus generating morphological integration. Artificial Cranial Deformation (ACD) occurs when the human skull is intentionally deformed, through the use of different deforming devices applied to the head while it is developing. Hence, ACD provides an interesting example to assess the degree to which biomechanical perturbations of the developing neurocranium impact on the degree of morphological integration in the skull as a whole. The main objective of this study was to assess how ACD affects the morphological integration of the skull. This was accomplished by comparing a sample of non-deformed crania and two sets of deformed crania (i.e. antero-posterior and oblique). Both developmental and static modularity and integration were assessed through Generalized Procrustes Analysis by considering the symmetric and asymmetric components of variation in adults, using 3D landmark coordinates as raw data. The presence of two developmental modules (i.e. viscero and neurocranium) in the skull was tested. Then, in order to understand how ACD affects morphological integration, the covariation pattern between the neuro and viscerocranium was examined in antero-posterior, oblique and non-deformed cranial categories using Partial Least-Squares. The main objective of this study was to assess how ACD affects the morphological integration of the skull. This was accomplished by comparing a sample of deformed (i.e. antero-posterior and oblique) and non-deformed crania. Hence, differences in integration patterns were compared between groups. The obtained results support the modular organization of the human skull in the two analyzed modules. The integration analyses show that the oblique ACD style differentially affects the static morphological integration of the skull by increasing the covariance between neuro and viscerocranium in a more constrained way than in antero-posterior and non-deformed skulls. In addition, the antero-posterior ACD style seems to affect the developmental integration of the skull by directing the covariation pattern in a more defined manner as compared to the other cranial categories.

Variability, agreement and reliability of MRI knee landmarks

Surface mesh reconstructions of bones are often required to define landmark-based coordinate systems, regions of interest and morphological features when studying the soft tissues of the knee from MRI scans. This study reports the variability, agreement and reliability of osseous landmarks to better understand their downstream effects. Fifteen landmarks were defined on the distal femur and twelve on the proximal tibia. Surface meshes were created from twenty right knee MRI scans with a mean subject age of 30.9 years. A single observer identified landmarks on all twenty knees, while three observers repeated the observations three times on a subset of eight knees. All observations were aligned to the Procrustes mean shapes. Principal component analysis was used to study inter-subject variability and two-way ANOVA for inter- and intra-observer agreement and reliability. Inter-subject landmark variation ranged from 0.6 to 5.26 mm, while inter- and intra-observer agreement were at most 5.1 and 5.69 mm respectively. Between-observer reliability ranged from 0.07 to 0.98 while within-observer values were between 0.51 and 0.98. Landmarks derived from fitted spheres or circles often performed well, while most others had their poorest agreement or greatest variation limited to only one or two cardinal directions.

Changes in human mandibular shape during the Terminal Pleistocene-Holocene Levant

The transition to food production, exploitation of 'secondary' products (e.g., milk), and advances in cookware technology have affected all aspects of human life. The aim of the present study was to follow changes in mandibular form and shape throughout the terminal Pleistocene-Holocene Levant. The hemimandibles of four populations were included in this study: Natufian hunter-gatherers (n = 10), Pre-pottery Neolithic early farmers (n = 6), Chalcolithic farmers (n = 9), Roman-Byzantine (n = 16), and modern (n = 63) populations. A surface mesh of each mandible was reconstructed from CT or surface scans. Changes in mandibular form and shape were studied using the Procrustes-based geometric morphometrics method. Univariate and multivariate analyses were carried out to examine differences in size and shape between the studied populations. Our results reveal considerable temporal changes in mandibular shape throughout the Holocene Levant, mainly between the pre-agricultural population (the Natufian) and the succeeding ones, and between the post-industrial (the Modern) and the pre-industrial populations. A tendency for a reduction in mandibular size was identified between the pre-agricultural population and the farmers. Most regions of the mandible underwent shape changes. In conclusion, substantial changes in mandibular shape occurred throughout the Holocene Levant, especially following the agricultural revolution. These changes can be explained by the "masticatory-functional hypothesis".

Exploratory study of the three-dimensional morphological variation of the jaw associated to teeth loss

PURPOSE

The aim of this study is to evaluate the morphological variability in mandibles with different types of edentulism, comparing the use of traditional morphometrics and tridimensional geometric morphometrics.

METHODS

Traditional morphometrics and geometric morphometrics (GM) exploratory analysis, by principal components (PCs) and PC scores, were performed on a sample of 24 cadaveric hemi mandibles. A digital reconstruction of 3D surfaces of each specimen was obtained by CT scans segmentation. The mandibles were divided in three groups: full dentition (G1), partial edentition (G2) and total edentition (G3). The results of the two methods were compared in relation to the morphological variability determined with each method.

RESULTS

Both methods were consistent in terms of morphological variability between the defined groups. The main shape variations observed were a decrease in mandibular body height, a widening of the cross sectional morphology on the symphysis, a shorten-narrowed Ramus and a deeper sigmoid notch, in the partially or totally edentition groups, compared to the full dentition group.

DISCUSSION

The general patterns of morphological variations associated with edentulism that have been reported in literature could be visualized with GM method, which had not been previously used for this purpose. The GM methods could offer a more detailed definition of shape variations, which is critical in a clinical context. Moreover, GM allowed defining configurations of mean morphologies and an image library with different types of morphological variations.

The morphology of the human mandible: A computational modelling study

Cephalometric methods have been used to evaluate morphometric measurements of the mandible and quantify sex-related anatomical features; however, most studies to date employ a limited set of location-specific measurements without considering the entire three-dimensional anatomy of the mandible. The aims of this study were to develop statistical shape models (SSMs) of partially edentulous male and female mandibles to evaluate inter-subject morphological variability and secondly to assess the effectiveness of discrete clinical morphometric measurements in prediction of complete three-dimensional mandible geometry. Computed tomography images of forty partially edentulous female and twenty-five male subjects were obtained, and SSM developed using mesh fitting, rigid body registration and principal component analysis. Analysis of female and male SSMs showed that the variation along their first principal components was size-related. Sex-differentiating pure shape variations were found along the first principal component of size-normalised SSM and were observed to be most prominent in the symphysis and posterior ramus regions of the mandible. Seven morphometric measurements were found to characterise female and male shape prediction optimally. The capability to rapidly generate accurate patient-specific shape-predictive models of the mandible may be useful for implant development and pre-operative planning, particularly in the absence of bony structures following trauma or tumour resection.

Morphometric analysis of shape differences in Windover and Point Hope archaic human mandibles

OBJECTIVES

The mandible can provide valuable information on both the life history and genetic makeup of Archaic human populations. The following analysis tests two hypotheses: (a) that there are significant differences in morphology in mandibular shape between the genders amongst Archaic North American Homo sapiens and (b) that there is a significant difference in variance in mandibular shape between Archaic Windover and Point Hope.

MATERIALS AND METHODS

A sample made from mandible specimens taken from both populations is subjected to Principal Component Analyses (PCA). The component scores from the PCAs are subjected to both a Multivariate Analysis of Covariance (mancova) and a general Multivariate Analysis of Variance (manova) to determine whether significant differences in variance exist between the sexes and the populations.

RESULTS

The mancova found that there are no significant interactions between the PC scores in population, sex, or size. Significant differences in variance were found between males and females and between the Windover and Point Hope populations.

CONCLUSIONS

Differences in variance observed between the populations are suspected to be due to differences in subsistence strategies and possibly non-masticatory utilizations of teeth. Differences in variance between the genders are suspected to be genetic in origin.

Sex estimation from cranial morphological traits: Use of the methods across American Indians, modern North Americans, and ancient Egyptians

This paper focuses on estimating sex by visual assessment of human cranial morphology. Practitioners in the field report variation in sexual dimorphism across populations. This study evaluates again the general hypothesis that populations vary in their pattern of sexual dimorphism. Specifically, the study tests the degree of expression of four cranial morphological traits (glabella, supraorbital margins, nuchal crest, and mastoid process) across three samples from different time periods and which vary in sociocultural transitions: 1) modern Americans of rural and urban areas spanning the last 186 years; 2) Dynastic Egyptians; and 3) Averbuch American Indians, spanning approximately 1255 CE to 1425 CE, from the southeastern United States. These three populations were specifically chosen for sampling as they represent distinct temporal and groups of varied ancestral composition. Crania from these samples were scored 1-5, with 1 being consistent with expected female morphology. The estimated sex was compared to either documented sex (when available) or discriminant functions derived from craniometrics. Freeman-Fisher-Halton tests examined sample differences, within sexes, affecting the visual assessment method. Post hoc tests were applied to pinpoint where the differences lie between the samples. The findings of this study support the hypothesis that the method does not estimate the sex of crania from all populations in the same manner, indicating that populations display differing patterns of sexual dimorphism. However, understanding these patterns and adjusting for how the method is applied will lead to reliable assessments. A relative frequency table and graphs of distributions are provided for practitioners who can use the information to make successful assessments of sex.

A 3D characterization method of geometric variation in edentulous mandibles

PURPOSE

The aim of this study was to perform an exploratory analysis of the morphological variations of mandibles at diverse states of edentulousness using tridimensional geometric morphometrics.

METHODS

Twelve cadaveric mandibles were selected and divided in three groups: dentate (G1), partially edentate (G2) and totally edentate (G3). CT scans, segmentation and digital reconstruction of 3D surfaces of each specimen was made. Thirteen landmarks were defined; the measurement error was determined and 3D morphometrics exploratory analysis by principal components (PCs) and PC scores was performed.

RESULTS

The principal shape variations in G2 and G3 compared to G1 can be summarized as follows: (1) decrease in the mid body mandibular height of 24% in G2 and 41% in G3, (2) decrease of symphysis height of 16% in G2 and 37% in G3, (3) a decrease in posterior mandibular height of 30% in both G1 and G2, (4) a deeper sigmoid notch also in both groups and finally (5) a widening of 7.7% in the cross sectional morphology on the symphysis in G3.

CONCLUSIONS

The 3D morphometric methods, combined with surface morphing tools confirmed the main patterns of bone changes in edentulous mandibles, referenced in the literature. The average 3D mandibular morphologies of each edentulousness state group was also defined. These methods could offer more accurate definition of shape variations, which is critical in a clinical context. This study provides clinicians with highlights of 3D morphological mandibular variations at different states of edentulism and not only in 2D projections as they are currently described. The 3D surface model for each group in PDF3D file format, are include in supplementary material.

Who were the Nataruk people? Mandibular morphology among late Pleistocene and early Holocene fisher-forager populations of West Turkana (Kenya)

Africa is the birthplace of the species Homo sapiens, and Africans today are genetically more diverse than other populations of the world. However, the processes that underpinned the evolution of African populations remain largely obscure. Only a handful of late Pleistocene African fossils (∼50-12 Ka) are known, while the more numerous sites with human fossils of early Holocene age are patchily distributed. In particular, late Pleistocene and early Holocene human diversity in Eastern Africa remains little studied, precluding any analysis of the potential factors that shaped human diversity in the region, and more broadly throughout the continent. These periods include the Last Glacial Maximum (LGM), a moment of extreme aridity in Africa that caused the fragmentation of population ranges and localised extinctions, as well as the 'African Humid Period', a moment of abrupt climate change and enhanced connectivity throughout Africa. East Africa, with its range of environments, may have acted as a refugium during the LGM, and may have played a critical biogeographic role during the heterogene`ous environmental recovery that followed. This environmental context raises a number of questions about the relationships among early Holocene African populations, and about the role played by East Africa in shaping late hunter-gatherer biological diversity. Here, we describe eight mandibles from Nataruk, an early Holocene site (∼10 Ka) in West Turkana, offering the opportunity of exploring population diversity in Africa at the height of the 'African Humid Period'. We use 3D geometric morphometric techniques to analyze the phenotypic variation of a large mandibular sample. Our results show that (i) the Nataruk mandibles are most similar to other African hunter-fisher-gatherer populations, especially to the fossils from Lothagam, another West Turkana locality, and to other early Holocene fossils from the Central Rift Valley (Kenya); and (ii) a phylogenetic connection may have existed between these Eastern African populations and some Nile Valley and Maghrebian groups, who lived at a time when a Green Sahara may have allowed substantial contact, and potential gene flow, across a vast expanse of Northern and Eastern Africa.

Human mandibular shape is associated with masticatory muscle force

Understanding how and to what extent forces applied to the mandible by the masticatory muscles influence its form, is of considerable importance from clinical, anthropological and evolutionary perspectives. This study investigates these questions. Head CT scans of 382 adults were utilized to measure masseter and temporalis muscle cross-sectional areas (CSA) as a surrogate for muscle force, and 17 mandibular anthropometric measurements. Sixty-two mandibles of young individuals (20–40 years) whose scans were without artefacts (e.g., due to tooth filling) were segmented and landmarked for geometric morphometric analysis. The association between shape and muscle CSA (controlled for size) was assessed using two-block partial least squares analysis. Correlations were computed between mandibular variables and muscle CSAs (all controlled for size). A significant association was found between mandibular shape and muscle CSAs, i.e. larger CSAs are associated with a wider more trapezoidal ramus, more massive coronoid, more rectangular body and a more curved basal arch. Linear measurements yielded low correlations with muscle CSAs. In conclusion, this study demonstrates an association between mandibular muscle force and mandibular shape, which is not as readily identified from linear measurements. Retrodiction of masticatory muscle force and so of mandibular loading is therefore best based on overall mandibular shape.

Mechanical implications of the mandibular coronoid process morphology in Neandertals

OBJECTIVES

Among the diagnostic features of the Neandertal mandible are the broad base of the coronoid process and its straight posterior margin. The adaptive value of these (and other) anatomical features has been linked to the Neandertal's need to cope with a large gape. The present study aims to test this hypothesis with regard to the morphology of the coronoid process.

MATERIALS AND METHODS

This admittedly simple, intuitive hypothesis was tested here via a comparative finite-element study of the primitive versus modified state of the coronoid process, using two-dimensional models of the mandible.

RESULTS

Our simulations demonstrate that a large gape has an unfavorable effect on the primitive state of the coronoid process: the diagonal, almost horizontal, component of the temporalis muscle resultant (relative to the long axis of the coronoid process) bends the process in the sagittal plane. Furthermore, we show that the modification of the coronoid process morphology alone reduces the process' bending in a wide gape increasing the compression to tension ratio.

DISCUSSION

These results provide indirect evidence in support of the hypothesis that the modification of the coronoid process in Neandertals is necessary for enabling their mandible to cope with a large gape.

A reassessment of the Montmaurin-La Niche mandible (Haute Garonne, France) in the context of European Pleistocene human evolution

We here present a comparative study of the Montmaurin-LN Middle Pleistocene mandible (Haute-Garonne, France). This mandible, of which its right and left molar series are preserved in situ, was found in La Niche cave (Montmaurin's karst system) in 1949, and was first attributed to the 'Mindel-Riss' interglacial (= MIS 9 to 11) based on its geological context. Later studies based on geological and faunal evidence have attributed the Montmaurin-LN mandible to MIS 7. Following a detailed morphological and metric comparative study of the mandible in the 1970s, it was interpreted in the light of a still limited fossil record and the prevailing paradigm back then. Waiting for geochronological studies in the forthcoming years, here we review the main morphological and metrical features of this mandible and its molars, which have been reassessed in the framework of a remarkably enlarged Pleistocene fossil record since the mandible was first described, and our current, more in-depth understanding of human evolution in Europe. Using a selection of mandibular features with potential taxonomic signal we have found that the Montmaurin-LN mandible shares only a few derived traits with Neandertals. Our analyses reveal that this mandible is more closely related to the ancient specimens from the African and Eurasian Early and Middle Pleistocene, particularly due to the presence of primitive features of the Homo clade. In contrast, the external morphology of the molars is clearly similar to that of Neandertals. The results are assessed in the light of the present competing hypotheses used to explain the European hominin fossil record.

Size, shape, and sex-dependent variation in force production by crayfish chelae

The ability to generate large closing forces is important for many animals. Several studies have demonstrated that bite or pinching force capacity is usually related to the linear dimensions of the closing apparatus. However, relatively few studies have applied geometric morphometrics to examine the effects of size-independent shape on force production, particularly in studies of crustacean pinching force. In this study, we utilized traditional and geometric morphometric techniques to compare the pinching force of Procambarus clarkii crayfish to their chela morphology. We found that males possessed larger chelae and pinched harder than females, but that their chela shape and size were weak predictors of strength. Female pinching force was significantly affected by both chela size and shape, with shape variation along the short axis of the claw contributing most to pinching force. We discuss our results in the context of reliable signaling of strength by males and females, and the different selective forces acting on chela shape in the two sexes.

Environment-Related Variation in the Human Mid-Face

Previous studies that have examined mid-facial morphology in geographically dispersed and genetically diverse groups of humans have shown a strong adaptation of the nasal part to extreme cold environments, which was not observed in non-Arctic regions. However, it remains unclear whether different parts of the mid-face area show independent adaptation to nonpolar climates, and if so, how this adaptation impacted the morphology. To address this question, we investigated potential associations between climatic variables and the mid-facial shape in 14 populations, focusing on four aspects of the morphology: total shape, zygomatic, nasal and alveolar. The results show that when the genetic distance between populations is not considered, all aspects of the morphology are strongly correlated with all climatic variables. When the genetic distance is considered, significant correlations remain only for the zygomatic, and nasal parts with temperature, and for the nasal part and alveolar with sunshine exposure. A strong but probably artificial correlation of the alveolar with atmospheric pressure is also observed. Additionally, partial least square analyses indicate that tropical and subtropical environments are associated with smaller zygomatic and more triangular nose aperture compared to more temperate environments. These findings suggest that temperate and tropical climates have induced adaptation of zygomatic and nasal parts of the mid-face in humans, and that this adaptation was probably driven by temperature and sunlight exposure conditions. Anat Rec, 300:238-250, 2017. © 2016 Wiley Periodicals, Inc.

A PCA-Based method for determining craniofacial relationship and sexual dimorphism of facial shapes

Previous studies have used principal component analysis (PCA) to investigate the craniofacial relationship, as well as sex determination using facial factors. However, few studies have investigated the extent to which the choice of principal components (PCs) affects the analysis of craniofacial relationship and sexual dimorphism. In this paper, we propose a PCA-based method for visual and quantitative analysis, using 140 samples of 3D heads (70 male and 70 female), produced from computed tomography (CT) images. There are two parts to the method. First, skull and facial landmarks are manually marked to guide the model's registration so that dense corresponding vertices occupy the same relative position in every sample. Statistical shape spaces of the skull and face in dense corresponding vertices are constructed using PCA. Variations in these vertices, captured in every principal component (PC), are visualized to observe shape variability. The correlations of skull- and face-based PC scores are analysed, and linear regression is used to fit the craniofacial relationship. We compute the PC coefficients of a face based on this craniofacial relationship and the PC scores of a skull, and apply the coefficients to estimate a 3D face for the skull. To evaluate the accuracy of the computed craniofacial relationship, the mean and standard deviation of every vertex between the two models are computed, where these models are reconstructed using real PC scores and coefficients. Second, each PC in facial space is analysed for sex determination, for which support vector machines (SVMs) are used. We examined the correlation between PCs and sex, and explored the extent to which the choice of PCs affects the expression of sexual dimorphism. Our results suggest that skull- and face-based PCs can be used to describe the craniofacial relationship and that the accuracy of the method can be improved by using an increased number of face-based PCs. The results show that the accuracy of the sex classification is related to the choice of PCs. The highest sex classification rate is 91.43% using our method.

Talking heads: Morphological variation in the human mandible over the last 500 years in the Netherlands

The primary aim of this paper is to assess patterns of morphological variation in the mandible to investigate changes during the last 500 years in the Netherlands. Three-dimensional geometric morphometrics is used on data collected from adults from three populations living in the Netherlands during three time-periods. Two of these samples come from Dutch archaeological sites (Alkmaar, 1484-1574, n=37; and Middenbeemster, 1829-1866, n=51) and were digitized using a 3D laser scanner. The third is a modern sample obtained from MRI scans of 34 modern Dutch individuals. Differences between mandibles are dominated by size. Significant differences in size are found among samples, with on average, males from Alkmaar having the largest mandibles and females from Middenbeemster having the smallest. The results are possibly linked to a softening of the diet, due to a combination of differences in food types and food processing that occurred between these time-periods. Differences in shape are most noticeable between males from Alkmaar and Middenbeemster. Shape differences between males and females are concentrated in the symphysis and ramus, which is mostly the consequence of sexual dimorphism. The relevance of this research is a better understanding of the anatomical variation of the mandible that can occur over an evolutionarily short time, as well as supporting research that has shown plasticity of the mandibular form related to diet and food processing. This plasticity of form must be taken into account in phylogenetic research and when the mandible is used in sex estimation of skeletons.

Of Kith and Kin: Perceptual Enrichment, Expectancy, and Reciprocity in Face Perception

Race powerfully affects perceivers' responses to faces, promoting biases in attention, classification, and memory. To account for these diverse effects, we propose a model that integrates social cognitive work with two prominent accounts of visual processing: perceptual learning and predictive coding. Our argument is that differential experience with a racial ingroup promotes both (a) perceptual enrichment, including richer, more well-integrated visual representations of ingroup relative to outgroup faces, and (b) expectancies that ingroup faces are normative, which influence subsequent visual processing. By allowing for "top-down" expectancy-based processes, this model accounts for both experience- and non-experience-based influences, such as motivation, context, and task instructions. Fundamentally, we suggest that we treat race as an important psychological dimension because it structures our social environment, which in turn structures mental representation.

Spatial determinants of the mandibular curve of Spee in modern and archaic Homo

OBJECTIVES

The curve of Spee (COS) is a mesio-distally curved alignment of the canine through distal molar cusp tips in certain mammals including modern humans and some fossil hominins. In humans, the alignment varies from concave to flat, and previous studies have suggested that this difference reflects craniofacial morphology, including the degree of alveolar prognathism. However, the relationship between prognathism and concavity of the COS has not been tested in craniofacially variant populations. We tested the hypothesis that greater alveolar prognathism covaries with a flatter COS in African-American and European-American populations. We further examined this relationship in fossil Homo including Homo neanderthalensis and early anatomically modern Homo sapiens, which are expected to extend the amount of variation in the COS from the extant sample.

METHODS AND MATERIALS

These hypotheses were tested using three-dimensional geometric morphometrics. Landmarks were recorded from the skulls of 166 African-Americans, 123 European-Americans, and 10 fossil hominin mandible casts. Landmarks were subjected to generalized Procrustes analysis, principal components analysis, and two-block partial least squares analysis.

RESULTS

We documented covariation between the COS and alveolar prognathism such that relatively prognathic individuals have a flatter COS. Mandibular data from the fossil hominin taxa generally confirm and extend this correlation across a greater range of facial size and morphology in Homo.

DISCUSSION

Our results suggest that the magnitude of the COS is related to a suite of features associated with alveolar prognathism in modern humans and across anthropoids. We also discuss the implications for spatial interactions between the dental arches.

The relative correspondence of cranial and genetic distances in papionin taxa and the impact of allometric adjustments

The reconstruction of phylogenetic relationships in the primate fossil record is dependent upon a thorough understanding of the phylogenetic utility of craniodental characters. Here, we test three previously proposed hypotheses for the propensity of primate craniomandibular data to exhibit homoplasy, using a study design based on the relative congruence between cranial distance matrices and a consensus genetic distance matrix ("genetic congruence") for papionin taxa: 1) matrices based on cranial regions subjected to less masticatory strain are more genetically congruent than high-strain cranial matrices; 2) matrices based on cranial regions developing earlier in ontogeny are more genetically congruent than matrices based on regions that develop later; and 3) matrices based on cranial regions with greater anatomical/functional complexity are more genetically congruent than matrices based on anatomically simpler regions. Morphological distance matrices based on the shape of 15 different cranial regions, delineated on the basis of previous catarrhine studies, were statistically compared to a matrix of known genetic distances in papionins. Since sexual dimorphism and allometry are known to characterize this clade, several analytical iterations were conducted: 1) mixed-sex, male-only, and female-only analyses and 2) with and without an allometric scaling adjustment. Across all datasets, the chondrocranium matrix was the most consistently correlated with genetic distances, which is also consistent with previous studies of cercopithecoid taxa; however, there was no support for the internal predictions of the three hypotheses tested. Allometric scaling corrections had the largest impact on the genetic congruence of facial shape matrices, a result consistent with previous studies that have described facial homoplasy in papionin taxa. These findings differ from patterns described for hominoid taxa, suggesting that no single predictive criterion can explain phylogenetic utility of cranial datasets across catarrhine primate taxa. Many of the differences in morphological-genetic matrix correlations could result from different levels of phenotypic integration and evolvability in cercopithecoids and hominoids, suggesting that further study of these phenomena in extant primates is warranted.

Functional geometric morphometric analysis of masticatory system ontogeny in papionin primates

The three-dimensional configuration of the primate masticatory system is constrained by the need to maximize bite forces while avoiding distraction of the temporomandibular joint (TMJ). Within these bounds, shape variation has predictable effects on functional capacities such as mechanical advantage and gape. In this study, geometric morphometric analysis is used to investigate the ontogeny of masticatory function in papionin monkeys and test the hypothesis that biomechanical constraints determine the location of molar eruption. This "constrained eruption hypothesis" predicts that the distalmost molar (DMX) will occupy a consistent location anterior to the TMJ and that jaw adductor muscles will maintain consistent positions relative to both DMX and TMJ. Craniometric landmarks were digitized on cross-sectional ontogenetic series of nine papionin species. Form-space PCA of Procrustes residuals, visualization of Bookstein shape coordinates, and nonparametric ANOVA were used to identify ontogenetic shape trends and test for significant ontogenetic changes in relative landmark positions. In most taxa, DMX maintains a consistent position relative to the TMJ while the anterior dentition migrates anteriorly. Where significant intraspecific ontogenetic differences occur, they involve anterior migration of DMX in later dental stages, likely due to late adolescent growth of the posterior palate. Attachments of the anterior temporalis and deep masseter also maintain consistent positions relative to the TMJ; however, the superficial masseter migrates anteriorly throughout ontogeny. All muscle attachments migrate laterally relative to the TMJ, reflecting positive scaling of adductor PCSA. Overall, results support the constrained eruption hypothesis and suggest mechanisms by which functional capacity is maintained during ontogeny.

The ontogeny of the chin: an analysis of allometric and biomechanical scaling

The presence of a prominent chin in modern humans has been viewed by some researchers as an architectural adaptation to buttress the anterior corpus from bending stresses during mastication. In contrast, ontogenetic studies of mandibular symphyseal form suggest that a prominent chin results from the complex spatial interaction between the symphysis and surrounding soft tissue and skeletal anatomy during development. While variation in chin prominence is clearly influenced by differential growth and spatial constraints, it is unclear to what degree these developmental dynamics influence the mechanical properties of the symphysis. That is, do ontogenetic changes in symphyseal shape result in increased symphyseal bending resistance? We examined ontogenetic changes in the mechanical properties and shape of the symphysis using subjects from a longitudinal cephalometric growth study with ages ranging from 3 to 20+ years. We first examined whether ontogenetic changes in symphyseal shape were correlated with symphyseal vertical bending and wishboning resistance using multivariate regression. Secondly, we examined ontogenetic scaling of bending resistance relative to bending moment arm lengths. An ontogenetic increase in chin prominence was associated with decreased vertical bending resistance, while wishboning resistance was uncorrelated with ontogenetic development of the chin. Relative to bending moment arm lengths, vertical bending resistance scaled with significant negative allometry whereas wishboning resistance scaled isometrically. These results suggest a complex interaction between symphyseal ontogeny and bending resistance, and indicate that ontogenetic increases in chin projection do not provide greater bending resistance to the mandibular symphysis.

Early modern humans and morphological variation in Southeast Asia: fossil evidence from Tam Pa Ling, Laos

Little is known about the timing of modern human emergence and occupation in Eastern Eurasia. However a rapid migration out of Africa into Southeast Asia by at least 60 ka is supported by archaeological, paleogenetic and paleoanthropological data. Recent discoveries in Laos, a modern human cranium (TPL1) from Tam Pa Ling‘s cave, provided the first evidence for the presence of early modern humans in mainland Southeast Asia by 63-46 ka. In the current study, a complete human mandible representing a second individual, TPL 2, is described using discrete traits and geometric morphometrics with an emphasis on determining its population affinity. The TPL2 mandible has a chin and other discrete traits consistent with early modern humans, but it retains a robust lateral corpus and internal corporal morphology typical of archaic humans across the Old World. The mosaic morphology of TPL2 and the fully modern human morphology of TPL1 suggest that a large range of morphological variation was present in early modern human populations residing in the eastern Eurasia by MIS 3.