Efficacy of diffeomorphic surface matching and 3D geometric morphometrics for taxonomic discrimination of Early Pleistocene hominin mandibular molars

Large deformation diffeomorphic mapping of 3D shape variation reveals two distinct mandible and head capsule morphs in Atta vollenweideri leaf-cutter worker ants

Ants are crucial ecosystem engineers, and their ecological success is facilitated by a division of labour among sterile "workers". In some ant lineages, workers have undergone further morphological differentiation, resulting in differences in body size, shape, or both. Distinguishing between changes in size and shape is not trivial. Traditional approaches based on allometry reduce complex 3D shapes into simple linear, areal, or volume metrics; modern approaches using geometric morphometrics typically rely on landmarks, introducing observer bias and a trade-off between effort and accuracy. Here, we use a landmark-free method based on large deformation diffeomorphic metric mapping (LDDMM) to assess the co-variation of size and 3D shape in the mandibles and head capsules of Atta vollenweideri leaf-cutter ants, a species exhibiting extreme worker size-variation. Body mass varied by more than two orders of magnitude, but a shape atlas created via LDDMM on μ-CT-derived 3D mesh files revealed only two distinct head capsule and mandibles shapes-one for the minims (body mass < 1 mg) and one for all other workers. We discuss the functional significance of the identified 3D shape variation, and its implications for the evolution of extreme polymorphism in Atta.

New craniodental fossils of Paranthropus robustus from Kromdraai, South Africa (2014-2017 excavations)

Since the initial discovery of Paranthropus robustus at the site of Kromdraai in 1938, the hypodigm of this species has been expanded by subsequent work at the localities of Swartkrans and Drimolen, with a few fossils also known from Cooper's D, Gondolin and Sterkfontein Member 5. Beginning in 2014, systematic excavations at Kromdraai uncovered a large and previously unknown fossiliferous area, shedding light on Units O and P in the earliest part of the site's stratigraphic sequence. The aim of this paper is to provide detailed descriptions and illustrations of 30 P. robustus craniodental specimens recovered between 2014 and 2017 within the Unit P deposits at Kromdraai. This new sample predates all prior conspecific specimens found at this site (including the holotype of P. robustus from Kromdraai, TM 1517). Its basic dental morphology dimensions and cranial features are compared in a preliminary analysis with other P. robustus samples. The P. robustus sample from Kromdraai Unit P documents previously unknown portions of the P. robustus juvenile cranium. The new dental and cranial remains aid in the exploration of potential morphological distinctions between site-specific P. robustus samples and are compared favorably in size and morphology with the small P. robustus specimens from Drimolen (e.g., DNH 7). These findings do not support the hypothesis that the specimens from Drimolen belong to a different taxonomic group. Instead, they reinforce the presence of a significant degree of sexual dimorphism within P. robustus. The Kromdraai Unit P specimens also contribute to the biodemographic profile of P. robustus. The notable prevalence of infants (i.e., juvenile individuals before the emergence of their first permanent molars) mirrors the natural mortality profiles observed in wild chimpanzees. This suggests a closer resemblance in the processes of accumulation in Kromdraai Unit P and Drimolen than at Swartkrans.

A reassessment of the distinctiveness of dryopithecine genera from the Iberian Miocene based on enamel-dentine junction geometric morphometric analyses

A vast diversity of catarrhines primates has been uncovered in the Middle to Late Miocene (12.5-9.6 Ma) of the Vallès-Penedès Basin (northeastern Spain), including several hominid species (Pierolapithecus catalaunicus, Anoiapithecus brevirostris, Dryopithecus fontani, Hispanopithecus laietanus, and Hispanopithecus crusafonti) plus some remains attributed to 'Sivapithecus' occidentalis (of uncertain taxonomic validity). However, Pierolapithecus and Anoiapithecus have also been considered junior synonyms of Dryopithecus by some authors, which entail a lower generic diversity and an inflated intrageneric variation of the latter genus. Since the distinction of these taxa partly relies on dental features, the detailed and quantitative analysis of tooth shape might help disentangling the taxonomic diversity of these Miocene hominids. Using diffeomorphic surface matching and three-dimensional geometric morphometrics, we investigate the enamel-dentine junction shape (which is a reliable taxonomic proxy) of these Miocene hominids, with the aim of investigating their degree of intra- and intergeneric variation compared with that of extant great ape genera. We conducted statistical analyses, including between-group principal component analyses, canonical variate analyses, and permutation tests, to investigate whether the individual and combined (i.e., Dryopithecus s.l.) variation of the extinct genera exceeds that of the extant great apes. Our results indicate that Pierolapithecus, Anoiapithecus, Dryopithecus, and Hispanopithecus show morphological differences of enamel-dentine junction shape relative to the extant great apes that are consistent with their attribution to different genera. Specifically, the variation displayed by the Middle Miocene taxa combined exceeds that of extant great ape genera, thus undermining the single-genus hypothesis. 'Sivapithecus' occidentalis specimens fall close to Dryopithecus but in the absence of well-preserved comparable teeth for Pierolapithecus and Anoiapithecus, their taxonomic attribution remains uncertain. Among the Hispanopithecus sample, IPS1802 from Can Llobateres stands out and might either be an outlier in terms of morphology, or represent another dryopithecine taxon.

New insights into the variability of upper airway morphology in modern humans

The biological adaptation of the human lineage to its environment is a recurring question in paleoanthropology. Particularly, how eco-geographic factors (e.g., environmental temperature and humidity) have shaped upper airway morphology in hominins have been subject to continuing debate. Nasal shape is the result of many intertwined factors that include, but are not limited to, genetic drift, sexual selection, or adaptation to climate. A quantification of nasal airway (NA) morphological variation in modern human populations is crucial to better understand these multiple factors. In the present research, we study 195 in vivo CT scans of adult individuals collected in five different geographic areas (Chile, France, Cambodia, Russia, and South Africa). After segmentation of the nasal airway, we reconstruct 3D meshes that are analyzed with a landmark-free geometric morphometrics method based on surface deformation. Our results highlight subtle but statistically significant morphological differences between our five samples. The two morphologically closest groups are France and Russia, whose NAs are longer and narrower, with an important protrusion of the supero-anterior part. The Cambodian sample is the most morphologically distinct and clustered sample, with a mean NA that is wider and shorter. On the contrary, the Chilean sample form the most scattered cluster with the greatest intra-population variation. The South African sample is morphologically close to the Cambodian sample, but also partially overlaps the French and Russian variation. Interestingly, we record no correlation between NA volume and geographic groups, which raises the question of climate-related metabolic demands for oxygen consumption. The other factors of variation (sex and age) have no influence on the NA shape in our samples. However, NA volume varies significantly according both to sex and age: it is higher in males than in females and tends to increase with age. In contrast, we observe no effect of temperature or humidity on NA volume. Finally, we highlight the important influence of asymmetries related to nasal septum deviations in NA shape variation.

New fossils from Kromdraai and Drimolen, South Africa, and their distinctiveness among Paranthropus robustus

Most fossil hominin species are sampled with spatial, temporal or anatomical biases that can hinder assessments of their paleodiversity, and may not yield genuine evolutionary signals. We use new fossils from the Kromdraai (Unit P) and Drimolen sites (South Africa) to provide insights into the paleodiversity of the Lower Pleistocene robust australopith, Paranthropus robustus. Our focus is the morphology of the temporal bone and the relationships between size and shape (allometry) of the semi-circular canals (SCC), an aspect that has not yet been investigated among southern African australopiths. We find significant size and shape SCC differences between P. robustus from Kromdraai, Drimolen and Swartkrans. This site-related variation is consistent with other differences observed on the temporal bone. P. robustus from Kromdraai Unit P is distinctive because of its smaller temporal bone and SCC, and its proportionally less developed posterior SCC, independently of age and sex. We emphasize the importance of allometry to interpret paleodiversity in P. robustus as either the consequence of differences in body size, or as yet unknown factors. Some features of the inner ear of P. robustus represent directional selection soon after its origin, whereas the size and shape variations described here may result from evolutionary changes.

Asymmetry of Endocast Surface Shape in Modern Humans Based on Diffeomorphic Surface Matching

Brain asymmetry is associated with handedness and cognitive function, and is also reflected in the shape of endocasts. However, comprehensive quantification of the asymmetry in endocast shapes is limited. Here, we quantify and visualize the variation of endocast asymmetry in modern humans using diffeomorphic surface matching. Our results show that two types of lobar fluctuating asymmetry contribute most to global asymmetry variation. A dominant pattern of local directional asymmetry is shared in the majority of the population: (1) the left occipital pole protrudes more than the right frontal pole in the left-occipital and right-frontal petalial asymmetry; (2) the left Broca’s cap appears to be more globular and bulges laterally, anteriorly, and ventrally compared to the right side; and (3) the asymmetrical pattern of the parietal is complex and the posterior part of the right temporal lobes are more bulbous than the contralateral sides. This study confirms the validity of endocasts for obtaining valuable information on encephalic asymmetries and reveals a more complicated pattern of asymmetry of the cerebral lobes than previously reported. The endocast asymmetry pattern revealed here provides more shape information to explore the relationships between brain structure and function, to re-define the uniqueness of human brains related to other primates, and to trace the timing of the human asymmetry pattern within hominin lineages.

Dental data challenge the ubiquitous presence of Homo in the Cradle of Humankind

The origins of Homo, as well as the diversity and biogeographic distribution of early Homo species, remain critical outstanding issues in paleoanthropology. Debates about the recognition of early Homo, first appearance dates, and taxonomic diversity within Homo are particularly important for determining the role that southern African taxa may have played in the origins of the genus. The correct identification of Homo remains also has implications for reconstructing phylogenetic relationships between species of Australopithecus and Paranthropus, and the links between early Homo species and Homo erectus. We use microcomputed tomography and landmark-free deformation-based three-dimensional geometric morphometrics to extract taxonomically informative data from the internal structure of postcanine teeth attributed to Early Pleistocene Homo in the southern African hominin-bearing sites of Sterkfontein, Swartkrans, Drimolen, and Kromdraai B. Our results indicate that, from our sample of 23 specimens, only 4 are unambiguously attributed to Homo, 3 of them coming from Swartkrans member 1 (SK 27, SK 847, and SKX 21204) and 1 from Sterkfontein (Sts 9). Three other specimens from Sterkfontein (StW 80 and 81, SE 1508, and StW 669) approximate the Homo condition in terms of overall enamel-dentine junction shape, but retain Australopithecus-like dental traits, and their generic status remains unclear. The other specimens, including SK 15, present a dominant australopith dental signature. In light of these results, previous dietary and ecological interpretations can be reevaluated, showing that the geochemical signal of one tooth from Kromdraai (KB 5223) and two from Swartkrans (SK 96 and SKX 268) is consistent with that of australopiths.

A Middle Pleistocene Denisovan molar from the Annamite Chain of northern Laos

The Pleistocene presence of the genus Homo in continental Southeast Asia is primarily evidenced by a sparse stone tool record and rare human remains. Here we report a Middle Pleistocene hominin specimen from Laos, with the discovery of a molar from the Tam Ngu Hao 2 (Cobra Cave) limestone cave in the Annamite Mountains. The age of the fossil-bearing breccia ranges between 164–131 kyr, based on the Bayesian modelling of luminescence dating of the sedimentary matrix from which it was recovered, U-series dating of an overlying flowstone, and U-series–ESR dating of associated faunal teeth. Analyses of the internal structure of the molar in tandem with palaeoproteomic analyses of the enamel indicate that the tooth derives from a young, likely female, Homo individual. The close morphological affinities with the Xiahe specimen from China indicate that they belong to the same taxon and that Tam Ngu Hao 2 most likely represents a Denisovan.

Evidence for the presence of Homo during the Middle Pleistocene is limited in continental Southeast Asia. Here, the authors report a hominin molar from Tam Ngu Hao 2 (Cobra Cave), dated to 164–131 kyr. They use morphological and paleoproteomic analysis to show that it likely belonged to a female Denisovan.

Shape analysis of the StW 578 calotte from Jacovec Cavern, Gauteng (South Africa)

The fossiliferous deposits within the lower-lying Jacovec Cavern in the locality of Sterkfontein yielded valuable hominin remains, including the StW 578 specimen. Because StW 578 mainly preserves the calotte, the taxonomic status of this specimen has been a matter of discussion. Within this context, here we employed high-resolution microtomography and a landmark-free registration method to explore taxonomically diagnostic features in the external surface of the StW 578 calotte. Our comparative sample included adult humans and common chimpanzees as well as one Australopithecus africanus specimen (Sts 5). We partially restored the StW 578 calotte digitally and compared it to extant specimens and Sts 5 using a landmark-free registration based on smooth and invertible surface deformation. Our comparative shape analysis reveals morphological differences with extant humans, especially in the frontal bones, and with extant chimpanzees, as well as intriguing specificities in the morphology of the StW 578 parietal bones. Lastly, our study suggests morphological proximity between StW 578 and Sts 5. Given the intimate relationship between the brain and the braincase, as well as the integration of the hominin face and neurocranium, we suggest that cranial vault shape differences between StW 578 and extant humans, if confirmed by further analyses, could be either explained by differences in brain surface morphology or in the face. Besides providing additional information about the morphology of the Jacovec calotte that will be useful in future taxonomic discussion, this study introduces a new protocol for the landmark-free analysis of fossil hominin cranial shape.

Use of Different Digitization Methods for the Analysis of Cut Marks on the Oldest Bone Found in Brittany (France)

Archaeological 3D digitization of skeletal elements is an essential aspect of the discipline. Objectives are various: archiving of data (especially before destructive sampling for biomolecular studies for example), study or for pedagogical purposes to allow their manipulation. As techniques are rapidly evolving, the question that arises is the use of appropriate methods to answer the different questions and guarantee sufficient quality of information. The combined use of different 3D technologies for the study of a single Mesolithic bone fragment from Brittany (France) is here an opportunity to compare different 3D digitization methods. This oldest human bone of Brittany, a clavicle constituted of two pieces, was dug up from the mesolithic shell midden of Beg-er-Vil in Quiberon and dated from ca. 8200 to 8000 years BP. They are bound to post-mortem processing, realized on fresh bone in order to remove the integuments, which it is necessary to better qualify. The clavicle was studied through a process that combines advanced 3D image acquisition, 3D processing, and 3D printing with the goal to provide relevant support for the experts involved in the work. The bones were first studied with a metallographic microscopy, scanned with a CT scan, and digitized with photogrammetry in order to get a high quality textured model. The CT scan appeared to be insufficient for a detailed analysis; the study was thus completed with a µ-CT providing a very accurate 3D model of the bone. Several 3D-printed copies of the collarbone were produced in order to support knowledge sharing between the experts involved in the study. The 3D models generated from µCT and photogrammetry were combined to provide an accurate and detailed 3D model. This model was used to study desquamation and the different cut marks, including their angle of attack. These cut marks were also studied with traditional binoculars and digital microscopy. This last technique allowed characterizing their type, revealing a probable meat cutting process with a flint tool. This work of crossed analyses allows us to document a fundamental patrimonial piece, and to ensure its preservation. Copies are also available for the regional museums.

Further analyses of the structural organization of Homo luzonensis teeth: Evolutionary implications

The species Homo luzonensis has recently been described based on a set of dental and postcranial elements found at Callao Cave (Northern Luzon, Philippines) and dated to at least 50-67 ka. Seven postcanine maxillary teeth are attributed to this taxon, five of them belonging to the same individual (CCH6) and representing the holotype of H. luzonensis, whereas the isolated upper premolar CCH8 and the upper third molar CCH9 are paratypes of the species. The teeth are characterized by their small dimensions associated with primitive features, as also found in Homo floresiensis, another hominin having evolved in an insular environment of Southeast Asia. Postcranial bones of the hands and feet of H. luzonensis and H. floresiensis show Homo habilis-like or australopith-like features, whereas cranial and dental morphology are more consistent with the Asian Homo erectus morphology. Due to this mosaic morphology, the origin and phylogenetic relationships of both H. luzonensis and H. floresiensis are still debated. To test the hypotheses that H. luzonensis derives from H. erectus or from an earlier small-brained hominin, we analyzed the µCT scans of the teeth. We investigated both external and internal tooth structure using morphometric methods including: crown outline shape, tooth crown tissue proportions, enamel-dentine junction shape, and pulp morphology. Homo luzonensis external crown morphology aligns more with H. erectus than with H. habilis/H. rudolfensis. The internal structural organization of H. luzonensis teeth exhibits more affinities with that of H. erectus and H. floresiensis than with Neanderthals and modern humans. Our results suggest that both H. floresiensis and H. luzonensis likely evolved from some H. erectus groups that dispersed in the various islands of this region and became isolated until endemic speciation events occurred at least twice during the Pleistocene in insular environments.

Variation in Middle Stone Age mandibular molar enamel-dentine junction topography at Klasies River Main Site assessed by diffeomorphic surface matching

The morphology and variability of the Middle Stone Age (MSA) hominin fossils from Klasies River Main Site have been the focus of investigation for more than four decades. The mandibular remains have figured prominently in discussions relating to robusticity, size dimorphism, and symphyseal morphology. Variation in corpus size between the robust SAM-AP 6223 and the diminutive SAM-AP 6225 mandibles is particularly impressive, and the difference between the buccolingual diameters of their M₂s significantly exceeds recent human sample variation. SAM-AP 6223 and SAM-AP 6225 are the only Klasies specimens with homologous teeth (M₂ and M₃) that permit comparisons of crown morphology. While the differences in dental trait expression at the outer enamel surfaces of these molars are slight, diffeomorphic surface analyses of their underlying enamel-dentine junction (EDJ) topographies reveal differences that are well beyond the means of pairwise differences among comparative samples of Later Stone Age (LSA) Khoesan and recent African homologues. The EDJs of both SAM-AP 6225 molars and the SAM-AP 6223 M₃ fall outside the envelopes that define the morphospace of these two samples. Although the radiocarbon dated LSA individuals examined here differ by a maximum of some 7000 years, and the two Klasies jaws may differ by perhaps as much as 18,000 years, it is difficult to ascribe their differences to time alone. With reference to the morphoscopic traits by which the SAM-AP 6223 and SAM-AP 6225 EDJs differ, the most striking is the expression of the protoconid cingulum. This is very weakly developed on the SAM-AP 6223 molars and distinct in SAM-AP 6225. As such, this diminutive fossil exhibits a more pronounced manifestation of what is likely a plesiomorphic feature, thus adding to the morphological mosaicism that is evident in the Klasies hominin assemblage. Several possible explanations for the variation and mosaicism in this MSA sample are discussed.

Cochlear shape distinguishes southern African early hominin taxa with unique auditory ecologies

Insights into potential differences among the bony labyrinths of Plio-Pleistocene hominins may inform their evolutionary histories and sensory ecologies. We use four recently-discovered bony labyrinths from the site of Kromdraai to significantly expand the sample for Paranthropus robustus. Diffeomorphometry, which provides detailed information about cochlear shape, reveals size-independent differences in cochlear shape between P. robustus and Australopithecus africanus that exceed those among modern humans and the African apes. The cochlea of P. robustus is distinctive and relatively invariant, whereas cochlear shape in A. africanus is more variable, resembles that of early Homo, and shows a degree of morphological polymorphism comparable to that evinced by modern species. The curvature of the P. robustus cochlea is uniquely derived and is consistent with enhanced sensitivity to low-frequency sounds. Combined with evidence for selection, our findings suggest that sound perception shaped distinct ecological adaptations among southern African early hominins.

Insect morphometry is reproducible under average investigation standards

Morphometric research is being applied to a growing number and variety of organisms. Discoveries achieved via morphometric approaches are often considered highly transferable, in contrast to the tacit and idiosyncratic interpretation of discrete character states. The reliability of morphometric workflows in insect systematics has never been a subject of focused research, but such studies are sorely needed. In this paper, we assess the reproducibility of morphometric studies of ants where the mode of data collection is a shared routine.We compared datasets generated by eleven independent gaugers, that is, collaborators, who measured 21 continuous morphometric traits on the same pool of individuals according to the same protocol. The gaugers possessed a wide range of morphometric skills, had varying expertise among insect groups, and differed in their facility with measuring equipment. We used intraclass correlation coefficients (ICC) to calculate repeatability and reproducibility values (i.e., intra- and intergauger agreements), and we performed a multivariate permutational multivariate analysis of variance (PERMANOVA) using the Morosita index of dissimilarity with 9,999 iterations.The calculated average measure of intraclass correlation coefficients of different gaugers ranged from R = 0.784 to R = 0.9897 and a significant correlation was found between the repeatability and the morphometric skills of gaugers (p = 0.016). There was no significant association with the magnification of the equipment in the case of these rather small ants. The intergauger agreement, that is the reproducibility, varied between R = 0.872 and R = 0.471 (mean R = 0.690), but all gaugers arrived at the same two-species conclusion. A PERMANOVA test revealed no significant gauger effect on species identity (R 2 = 0.69, p = 0.58).Our findings show that morphometric studies are reproducible when observers follow the standard protocol; hence, morphometric findings are widely transferable and will remain a valuable data source for alpha taxonomy.

Comparative morphometric analyses of the deciduous molars of Homo naledi from the Dinaledi Chamber, South Africa

OBJECTIVES

The purpose of this study is to help elucidate the taxonomic relationship between Homo naledi and other hominins.

MATERIALS AND METHODS

Homo naledi deciduous maxillary and mandibular molars from the Dinaledi Chamber, South Africa were compared to those of Australopithecus africanus, Australopithecus afarensis, Paranthropus robustus, Paranthropus boisei, early Homo sp., Homo erectus, early Homo sapiens, Upper Paleolithic H. sapiens, recent southern African H. sapiens, and Neanderthals by means of morphometric analyses of crown outlines and relative cusp areas. The crown shapes were analyzed using elliptical Fourier analyses followed by principal component analyses (PCA). The absolute and relative cusp areas were obtained in ImageJ and compared using PCA and cluster analyses.

RESULTS

PCA suggests that the crown shapes and relative cusp areas of mandibular molars are more diagnostic than the maxillary molars. The H. naledi deciduous mandibular first and second molar (dm₁ and dm₂ ) do not have a strong affinity to any taxon in the comparative sample in all analyses. While the H. naledi dm₂ plots as an outlier in the relative cusp analysis, the H. naledi specimen fall closest to Australopithecus due to their relatively large metaconid, a primitive trait for the genus Homo. Although useful for differentiating Neanderthals from recent southern African H. sapiens and UP H. sapiens, the PCA of the relative cusp areas suggests that the deciduous maxillary second molars (dm² ) do not differentiate other groups. The three H. naledi dm² cuspal areas are variable and fall within the ranges of other Homo, as well as Australopithecus, and Paranthropus suggesting weak diagnostic utility.

DISCUSSION

This research provides another perspective on the morphology of, and variation within, H. naledi. The H. naledi deciduous molars do not consistently align with any genus or species in the comparative sample in either the crown shape or relative cusp analyses. This line of inquiry is consistent with other cranial and postcranial studies suggesting that H. naledi is unique.

Hominin diversity in East Asia during the Middle Pleistocene: A premolar endostructural perspective

Following the recent studies of East Asian mid-Middle to early Late Pleistocene hominin material, a large spectrum of morphological diversity has been recognized and the coexistence of archaic ('Homo erectus-like') and derived ('modern-like') dental morphological patterns has been highlighted. In fact, for most of these Chinese fossils, generally categorized as 'archaic Homo sapiens' or 'post-H. erectus Homo', the taxonomic attribution is a matter of contention. With the help of μCT techniques and a deformation-based 3D geometric morphometric approach, we focused on the morphological variation in the enamel-dentine junction (EDJ) of 18 upper and lower premolars from Chinese Middle Pleistocene hominins. We then compared our results with a number of fossil and modern human groups, including Early Pleistocene H. erectus from Sangiran; late Early Pleistocene hominins from Tighenif, Algeria; classic Neanderthals; and modern humans. Our results highlight an evolutionary/chronological trend of crown base reduction, elevation of EDJ topography, and EDJ surface simplification in the hominin groups studied here. Moreover, this study brings insights to the taxonomy/phylogeny of 6 late Middle Pleistocene specimens whose evolutionary placement has been debated for decades. Among these specimens, Changyang premolars show features that can be aligned with the Asian H. erectus hypodigm, whereas Panxian Dadong and Tongzi premolars are more similar to Late Pleistocene Homo. Compared with early to mid-Middle Pleistocene hominins in East Asia, late Middle Pleistocene hominins evince an enlarged morphological variation. A persistence of archaic morphotypes and possible admixture among populations during the late Middle Pleistocene are discussed.

A novel identification method using perceptual degree of concordance of occlusal surfaces calculated by a Python program

One of the important issues during the response to a mass disaster is the identification of victims. In this study, we verified the use of the occlusal morphology of molars for individual identification. The aim of this study was to establish a simple new method for identifying individuals from molar data. Using Python, we developed programming that included the perceptual Hash (pHash) function and the Hamming distance (HD) between antemortem data (AMD) and postmortem data (PMD). The AMD comprised 2,215 dental models. The PMD were selected from the AMD set and comprised 17 models from the same individual with changes over time. As a result, 16 PMD models (over 90%) were ranked in the top 5%. Although identification using only a single molar is difficult, there is the possibility of narrowing down victims' identity with high accuracy through verification using multiple teeth. This system is expected to be useful as a very simple method of identification.

A data-driven classification of 3D foot types by archetypal shapes based on landmarks

The taxonomy of foot shapes or other parts of the body is important, especially for design purposes. We propose a methodology based on archetypoid analysis (ADA) that overcomes the weaknesses of previous methodologies used to establish typologies. ADA is an objective, data-driven methodology that seeks extreme patterns, the archetypal profiles in the data. ADA also explains the data as percentages of the archetypal patterns, which makes this technique understandable and accessible even for non-experts. Clustering techniques are usually considered for establishing taxonomies, but we will show that finding the purest or most extreme patterns is more appropriate than using the central points returned by clustering techniques. We apply the methodology to an anthropometric database of 775 3D right foot scans representing the Spanish adult female and male population for footwear design. Each foot is described by a 5626 × 3 configuration matrix of landmarks. No multivariate features are used for establishing the taxonomy, but all the information gathered from the 3D scanning is employed. We use ADA for shapes described by landmarks. Women’s and men’s feet are analyzed separately. We have analyzed 3 archetypal feet for both men and women. These archetypal feet could not have been recovered using multivariate techniques.

Cochlear shape reveals that the human organ of hearing is sex-typed from birth

Sex differences in behavioral and neural characteristics can be caused by cultural influences but also by sex-based differences in neurophysiological and sensorimotor features. Since signal-response systems influence decision-making, cooperative and collaborative behaviors, the anatomical or physiological bases for any sex-based difference in sensory mechanisms are important to explore. Here, we use uniform scaling and nonparametric representations of the human cochlea, the main organ of hearing that imprints its adult-like morphology within the petrosal bone from birth. We observe a sex-differentiated torsion along the 3D cochlear curve in samples of 94 adults and 22 juvenile skeletons from cross-cultural contexts. The cochlear sexual dimorphism measured in our study allows sex assessment from the human skeleton with a mean accuracy ranging from 0.91 to 0.93 throughout life. We conclude that the human cochlea is sex-typed from an early post-natal age. This, for the first time, allows nondestructive sex determination of juveniles' skeletal remains in which the biomolecules are too degraded for study but in which the petrosal is preserved, one of the most common bone within archaeological assemblages. Our observed sex-typed cochlear shape from birth is likely associated with complex evolutionary processes in modern humans for reasons not yet fully understood.