The primitive brain of early Homo

The brains of modern humans differ from those of great apes in size, shape, and cortical organization, notably in frontal lobe areas involved in complex cognitive tasks, such as social cognition, tool use, and language. When these differences arose during human evolution is a question of ongoing debate. Here, we show that the brains of early Homo from Africa and Western Asia (Dmanisi) retained a primitive, great ape-like organization of the frontal lobe. By contrast, African Homo younger than 1.5 million years ago, as well as all Southeast Asian Homo erectus, exhibited a more derived, humanlike brain organization. Frontal lobe reorganization, once considered a hallmark of earliest Homo in Africa, thus evolved comparatively late, and long after Homo first dispersed from Africa.

Early development of the Neanderthal ribcage reveals a different body shape at birth compared to modern humans

Ontogenetic studies provide clues for understanding important paleobiological aspects of extinct species. When compared to that of modern humans, the adult Neanderthal thorax was shorter, deeper, and wider. This is related to the wide Neanderthal body and is consistent with their hypothetical large requirements for energy and oxygen. Whether these differences were already established at birth or appeared later during development is unknown. To delve into this question, we use virtual reconstruction tools and geometric morphometrics to recover the 3D morphology of the ribcages of four Neanderthal individuals from birth to around 3 years old: Mezmaiskaya 1, Le Moustier 2, Dederiyeh 1, and Roc de Marsal. Our results indicate that the comparatively deep and short ribcage of the Neanderthals was already present at birth, as were other skeletal species-specific traits. This morphology possibly represents the plesiomorphic condition shared with Homo erectus, and it is likely linked to large energetic requirements.

Reconstructing the Neanderthal brain using computational anatomy

The present study attempted to reconstruct 3D brain shape of Neanderthals and early Homo sapiens based on computational neuroanatomy. We found that early Homo sapiens had relatively larger cerebellar hemispheres but a smaller occipital region in the cerebrum than Neanderthals long before the time that Neanderthals disappeared. Further, using behavioural and structural imaging data of living humans, the abilities such as cognitive flexibility, attention, the language processing, episodic and working memory capacity were positively correlated with size-adjusted cerebellar volume. As the cerebellar hemispheres are structured as a large array of uniform neural modules, a larger cerebellum may possess a larger capacity for cognitive information processing. Such a neuroanatomical difference in the cerebellum may have caused important differences in cognitive and social abilities between the two species and might have contributed to the replacement of Neanderthals by early Homo sapiens.

Identification of in vivo Sulci on the External Surface of Eight Adult Chimpanzee Brains: Implications for Interpreting Early Hominin Endocasts

The only direct source of information about hominin brain evolution comes from the fossil record of endocranial casts (endocasts) that reproduce details of the external morphology of the brain imprinted on the walls of the braincase during life. Surface traces of sulci that separate the brain's convolutions (gyri) are reproduced sporadically on early hominin endocasts. Paleoneurologists rely heavily on published descriptions of sulci on brains of great apes, especially chimpanzees (humans' phylogenetically closest living relatives), to guide their identifications of sulci on ape-sized hominin endocasts. However, the few comprehensive descriptions of cortical sulci published for chimpanzees usually relied on post mortem brains, (now) antiquated terminology for some sulci, and photographs or line drawings from limited perspectives (typically right or left lateral views). The shortage of adequate descriptions of chimpanzee sulcal patterns partly explains why the identities of certain sulci on australopithecine endocasts (e.g., the inferior frontal and middle frontal sulci) have been controversial. Here, we provide images of lateral and dorsal surfaces of 16 hemispheres from 4 male and 4 female adult chimpanzee brains that were obtained using in vivo magnetic resonance imaging. Sulci on the exposed surfaces of the frontal, parietal, temporal, and occipital lobes are identified on the images based on their locations, positions relative to each other, and homologies known from comparative studies of cytoarchitecture in primates. These images and sulcal identifications exceed the quantity and quality of previously published illustrations of chimpanzee brains with comprehensively labeled sulci and, thus, provide a larger number of examples for identifying sulci on hominin endocasts than hitherto available. Our findings, even in a small sample like the present one, overturn published claims that australopithecine endocasts reproduce derived configurations of certain sulci in their frontal lobes that never appear on chimpanzee brains. The sulcal patterns in these new images also suggest that changes in two gyri that bridge between the parietal and occipital lobes may have contributed to cortical reorganization in early hominins. It is our hope that these labeled in vivo chimpanzee brains will assist future researchers in identifying sulci on hominin endocasts, which is a necessary first step in the quest to learn how and when the external morphology of the human cerebral cortex evolved from apelike precursors.

Femoral ontogeny in humans and great apes and its implications for their last common ancestor

Inferring the morphology of the last common ancestor of humans, chimpanzees and gorillas is a matter of ongoing debate. Recent findings and reassessment of fossil hominins leads to the hypothesis that the last common ancestor was not extant African ape-like. However, an African great-ape-like ancestor with knuckle walking features still remains plausible and the most parsimonious scenario. Here we address this question via an evolutionary developmental approach, comparing taxon-specific patterns of shape change of the femoral diaphysis from birth to adulthood in great apes, humans, and macaques. While chimpanzees and gorillas exhibit similar locomotor behaviors, our data provide evidence for distinct ontogenetic trajectories, indicating independent evolutionary histories of femoral ontogeny. Our data further indicate that anthropoid primates share a basic pattern of femoral diaphyseal ontogeny that reflects shared developmental constraints. Humans escaped from these constraints via differential elongation of femur.

Brain development is similar in Neanderthals and modern humans

While the braincase of adult Neanderthals had a similar volume to that of modern humans from the same period, differences in endocranial shape suggest that brain morphology differed between modern humans and Neanderthals. When and how these differences arose during evolution and development is a topic of ongoing research, with potential implications for species-specific differences in brain and cognitive development, and in life history [1,2]. Earlier research suggested that Neanderthals followed an ancestral mode of brain development, similar to that of our closest living relatives, the chimpanzees [2-4]. Modern humans, by contrast, were suggested to follow a uniquely derived mode of brain development just after birth, giving rise to the characteristically globular shape of the adult human brain case [2,4,5]. Here, we re-examine this hypothesis using an extended sample of Neanderthal infants. We document endocranial development during the decisive first two years of postnatal life. The new data indicate that Neanderthals followed largely similar modes of endocranial development to modern humans. These findings challenge the notion that human brain and cognitive development after birth is uniquely derived [2,4].

Neomorphosis and heterochrony of skull shape in dog domestication

The overall similarity of the skull shape of some dog breeds with that of juvenile wolves begs the question if and how ontogenetic changes such as paedomorphosis (evolutionary juvenilisation) played a role in domestication. Here we test for changes in patterns of development and growth during dog domestication. We present the first geometric morphometric study using ontogenetic series of dog and wolf crania, and samples of dogs with relatively ancestral morphology and from different time periods. We show that patterns of juvenile-to-adult morphological change are largely similar in wolves and domestic dogs, but differ in two ways. First, dog skulls show unique (neomorphic) features already shortly after birth, and these features persist throughout postnatal ontogeny. Second, at any given age, juvenile dogs exhibit skull shapes that resemble those of consistently younger wolves, even in dog breeds that do not exhibit a 'juvenilized' morphology as adults. These patterns exemplify the complex nature of evolutionary changes during dog domestication: the cranial morphology of adult dogs cannot simply be explained as either neomorphic or paedomorphic. The key to our understanding of dog domestication may lie in a closer comparative examination of developmental phases.

Individual-based modelling of population growth and diffusion in discrete time

Individual-based models (IBMs) of human populations capture spatio-temporal dynamics using rules that govern the birth, behavior, and death of individuals. We explore a stochastic IBM of logistic growth-diffusion with constant time steps and independent, simultaneous actions of birth, death, and movement that approaches the Fisher-Kolmogorov model in the continuum limit. This model is well-suited to parallelization on high-performance computers. We explore its emergent properties with analytical approximations and numerical simulations in parameter ranges relevant to human population dynamics and ecology, and reproduce continuous-time results in the limit of small transition probabilities. Our model prediction indicates that the population density and dispersal speed are affected by fluctuations in the number of individuals. The discrete-time model displays novel properties owing to the binomial character of the fluctuations: in certain regimes of the growth model, a decrease in time step size drives the system away from the continuum limit. These effects are especially important at local population sizes of <50 individuals, which largely correspond to group sizes of hunter-gatherers. As an application scenario, we model the late Pleistocene dispersal of Homo sapiens into the Americas, and discuss the agreement of model-based estimates of first-arrival dates with archaeological dates in dependence of IBM model parameter settings.

Effects of cranial integration on hominid endocranial shape

Because brains do not fossilize, the internal surface of the braincase (endocast) serves as an important source of information about brain growth, development, and evolution. Recent studies of endocranial morphology and development in great apes, fossil hominins, and modern humans have revealed taxon-specific differences. However, it remains to be investigated to which extent differences in endocranial morphology reflect differences in actual brain morphology and development, and to which extent they reflect different interactions of the brain and its case with the cranial base and face. Here we address this question by analyzing the effects of cranial integration on endocranial morphology. We test the 'spatial packing' and 'facial orientation' hypotheses, which propose that size and orientation of the neurocranium relative to the viscerocranium influence endocranial shape. Results show that a substantial proportion of endocranial shape variation along and across ontogenetic trajectories is due to cranial integration. Specifically, the uniquely globular shape of the human endocast mainly results from the combination of an exceptionally large brain with a comparatively small face. Overall, thus, cranial integration has pervasive effects on endocranial morphology, and only a comparatively small proportion of inter- and intra-taxon variation can directly be associated with variation in brain morphology.

Comparative analysis of dentognathic pathologies in the Dmanisi mandibles

OBJECTIVES

Due to the scarcity of the fossil record, in vivo changes in the dentognathic system of early Homo are typically documented at the level of individual fossil specimens, and it remains difficult to draw population-level inferences about dietary habits, diet-related activities and lifestyle from individual patterns of dentognathic alterations. The Plio-Pleistocene hominin sample from Dmanisi (Georgia), dated to 1.77 million years ago, offers a unique opportunity to study in vivo changes in the dentognathic system of individuals belonging to a single paleodeme of early Homo.

MATERIALS AND METHODS

We analyze dentognathic pathologies in the Dmanisi sample, and in comparative samples of modern Australian and Greenlander hunter-gatherer populations, applying clinical protocols of dentognathic diagnostics.

RESULTS

The Dmanisi hominins exhibit a similarly wide diversity and similar incidence of dentognathic pathologies as the modern human hunter-gatherer population samples investigated here. Dmanisi differs from the modern population samples in several respects: At young age tooth wear is already advanced, and pathologies are more prevalent. At old age, hypercementosis is substantial.

CONCLUSIONS

Results indicate that dentognathic pathologies and disease trajectories are largely similar in early Homo and modern humans, but that the disease load was higher in early Homo, probably as an effect of higher overall stress on the dentognathic system. Am J Phys Anthropol 160:229-253, 2016. © 2016 Wiley Periodicals, Inc.

POPULATION GENETICS. Genomic evidence for the Pleistocene and recent population history of Native Americans

How and when the Americas were populated remains contentious. Using ancient and modern genome-wide data, we found that the ancestors of all present-day Native Americans, including Athabascans and Amerindians, entered the Americas as a single migration wave from Siberia no earlier than 23 thousand years ago (ka) and after no more than an 8000-year isolation period in Beringia. After their arrival to the Americas, ancestral Native Americans diversified into two basal genetic branches around 13 ka, one that is now dispersed across North and South America and the other restricted to North America. Subsequent gene flow resulted in some Native Americans sharing ancestry with present-day East Asians (including Siberians) and, more distantly, Australo-Melanesians. Putative "Paleoamerican" relict populations, including the historical Mexican Pericúes and South American Fuego-Patagonians, are not directly related to modern Australo-Melanesians as suggested by the Paleoamerican Model.

Let bone and muscle talk together: a study of real and virtual dissection and its implications for femoral musculoskeletal structure of chimpanzees

Proximal femoral morphology and associated musculature are of special relevance to the understanding of hominoid locomotor systems. Knowledge of bone-muscle correspondence in extant hominoids forms an important comparative basis for inferring structure-function relationships in fossil hominids. However, there is still a lack of consensus on the correspondence between muscle attachment sites and surface morphology of the proximal femoral diaphysis in chimpanzees. Two alternative observations have been proposed regarding the attachment site positions of gluteus maximus (GM) and vastus lateralis (VL) relative to two prominent surface features of the proximal femoral diaphysis, the lateral spiral pilaster and the inferolateral fossa. Here, we use a combination of virtual and physical dissection in an attempt to identify the exact correspondence between muscle attachment sites and osteological features in two specimens of Pan troglodytes verus. The results show that the insertion of the GM tendon is consistently inferolateral to the lateral spiral pilaster, and that a part of the inferolateral fossa consistently forms the attachment site of the VL muscular fibers. While overall musculoskeletal features are similar in the two specimens examined in this study, GM and VL exhibit different degrees of segregation at the level of the inferolateral fossa. One specimen exhibited tendinous GM fibers penetrating the posteromedial part of VL, with both GM and VL inserting at the inferolateral fossa. In the other specimen, GM and VL were separated by a lateral intermuscular septum, which inserted into the inferolateral fossa. Variation of proximal femoral muscle attachments in chimpanzees is thus greater than previously thought. Our results indicate that a conspicuous osteological feature such as the inferolateral fossa does not necessarily correspond to the attachment site of a single muscle, but could serve as a boundary region between two muscles. Caution is thus warranted when interpreting the surface topography of muscle attachment sites and inferring locomotor functions.

Phenotypic variation in infants, not adults, reflects genotypic variation among chimpanzees and bonobos

Studies comparing phenotypic variation with neutral genetic variation in modern humans have shown that genetic drift is a main factor of evolutionary diversification among populations. The genetic population history of our closest living relatives, the chimpanzees and bonobos, is now equally well documented, but phenotypic variation among these taxa remains relatively unexplored, and phenotype-genotype correlations are not yet documented. Also, while the adult phenotype is typically used as a reference, it remains to be investigated how phenotype-genotye correlations change during development. Here we address these questions by analyzing phenotypic evolutionary and developmental diversification in the species and subspecies of the genus Pan. Our analyses focus on the morphology of the femoral diaphysis, which represents a functionally constrained element of the locomotor system. Results show that during infancy phenotypic distances between taxa are largely congruent with non-coding (neutral) genotypic distances. Later during ontogeny, however, phenotypic distances deviate from genotypic distances, mainly as an effect of heterochronic shifts between taxon-specific developmental programs. Early phenotypic differences between Pan taxa are thus likely brought about by genetic drift while late differences reflect taxon-specific adaptations.

Mammalian skull heterochrony reveals modular evolution and a link between cranial development and brain size

The multiple skeletal components of the skull originate asynchronously and their developmental schedule varies across amniotes. Here we present the embryonic ossification sequence of 134 species, covering all major groups of mammals and their close relatives. This comprehensive data set allows reconstruction of the heterochronic and modular evolution of the skull and the condition of the last common ancestor of mammals. We show that the mode of ossification (dermal or endochondral) unites bones into integrated evolutionary modules of heterochronic changes and imposes evolutionary constraints on cranial heterochrony. However, some skull-roof bones, such as the supraoccipital, exhibit evolutionary degrees of freedom in these constraints. Ossification timing of the neurocranium was considerably accelerated during the origin of mammals. Furthermore, association between developmental timing of the supraoccipital and brain size was identified among amniotes. We argue that cranial heterochrony in mammals has occurred in concert with encephalization but within a conserved modular organization.

A complete skull from Dmanisi, Georgia, and the evolutionary biology of early Homo

The site of Dmanisi, Georgia, has yielded an impressive sample of hominid cranial and postcranial remains, documenting the presence of Homo outside Africa around 1.8 million years ago. Here we report on a new cranium from Dmanisi (D4500) that, together with its mandible (D2600), represents the world's first completely preserved adult hominid skull from the early Pleistocene. D4500/D2600 combines a small braincase (546 cubic centimeters) with a large prognathic face and exhibits close morphological affinities with the earliest known Homo fossils from Africa. The Dmanisi sample, which now comprises five crania, provides direct evidence for wide morphological variation within and among early Homo paleodemes. This implies the existence of a single evolving lineage of early Homo, with phylogeographic continuity across continents.

Shared human-chimpanzee pattern of perinatal femoral shaft morphology and its implications for the evolution of hominin locomotor adaptations

BACKGROUND

Acquisition of bipedality is a hallmark of human evolution. How bipedality evolved from great ape-like locomotor behaviors, however, is still highly debated. This is mainly because it is difficult to infer locomotor function, and even more so locomotor kinematics, from fossil hominin long bones. Structure-function relationships are complex, as long bone morphology reflects phyletic history, developmental programs, and loading history during an individual's lifetime. Here we discriminate between these factors by investigating the morphology of long bones in fetal and neonate great apes and humans, before the onset of locomotion.

METHODOLOGY/PRINCIPAL FINDINGS

Comparative morphometric analysis of the femoral diaphysis indicates that its morphology reflects phyletic relationships between hominoid taxa to a greater extent than taxon-specific locomotor adaptations. Diaphyseal morphology in humans and chimpanzees exhibits several shared-derived features, despite substantial differences in locomotor adaptations. Orangutan and gorilla morphologies are largely similar, and likely represent the primitive hominoid state.

CONCLUSIONS/SIGNIFICANCE

These findings are compatible with two possible evolutionary scenarios. Diaphyseal morphology may reflect retained adaptive traits of ancestral taxa, hence human-chimpanzee shared-derived features may be indicative of the locomotor behavior of our last common ancestor. Alternatively, diaphyseal morphology might reflect evolution by genetic drift (neutral evolution) rather than selection, and might thus be more informative about phyletic relationships between taxa than about locomotor adaptations. Both scenarios are consistent with the hypothesis that knuckle-walking in chimpanzees and gorillas resulted from convergent evolution, and that the evolution of human bipedality is unrelated to extant great ape locomotor specializations.

The effect of age, sex, and physical activity on entheseal morphology in a contemporary Italian skeletal collection

Entheseal changes are traditionally included in a large array of skeletal features commonly referred to as "skeletal markers of activity." However, medical studies and recent anthropological analyses of identified skeletal series suggest a complex combination of physiological and biomechanical factors underlying the variability of such "markers." The aim of this study is to examine the relationship between age, sex, physical activity, and entheseal variability. To this end, 23 postcranial entheses are examined in a large (N = 484) Italian contemporary skeletal series using standardized scoring methods. The sample comprises subjects of known age, sex and, mostly, occupation. Results show a strong relationship between age and entheseal changes. Differences between sexes are also highlighted, while the effects of physical activity appear moderate. Altogether, our study indicates that entheseal morphology primarily reflects the age of an individual, while correlation with lifetime activity remains ambiguous.

Evolution of hominin cranial ontogeny

Hominin evolution is characterized by two main trends, transition to bipedality and increase in brain size. Fossil evidence shows that both trends had a major impact on the structure and function of the hominin skull. This chapter asks how evolutionary modification of the cranial ontogenetic program led to morphological reorganization of the hominin skull and ultimately to hominin cranial diversity. Three major mechanisms of evolutionary developmental reorganization are proposed: modified prenatal development of the cranial base and face reflects adaptation to bipedality; high rates of neurocranial growth during early postnatal ontogeny are essential to attain large brain sizes; taxon-specific modification of facial development reflects dietary adaptation and-in the genus Homo-a general trend toward neoteny.

Interactive multiscale tensor reconstruction for multiresolution volume visualization

Large scale and structurally complex volume datasets from high-resolution 3D imaging devices or computational simulations pose a number of technical challenges for interactive visual analysis. In this paper, we present the first integration of a multiscale volume representation based on tensor approximation within a GPU-accelerated out-of-core multiresolution rendering framework. Specific contributions include (a) a hierarchical brick-tensor decomposition approach for pre-processing large volume data, (b) a GPU accelerated tensor reconstruction implementation exploiting CUDA capabilities, and (c) an effective tensor-specific quantization strategy for reducing data transfer bandwidth and out-of-core memory footprint. Our multiscale representation allows for the extraction, analysis and display of structural features at variable spatial scales, while adaptive level-of-detail rendering methods make it possible to interactively explore large datasets within a constrained memory footprint. The quality and performance of our prototype system is evaluated on large structurally complex datasets, including gigabyte-sized micro-tomographic volumes.

Femoral morphology and femoropelvic musculoskeletal anatomy of humans and great apes: a comparative virtopsy study

The proximal femoral morphology of fossil hominins is routinely interpreted in terms of muscular topography and associated locomotor modes. However, the detailed correspondence between hard and soft tissue structures in the proximal femoral region of extant great apes is relatively unknown, because dissection protocols typically do not comprise in-depth osteological descriptions. Here, we use computed tomography and virtopsy (virtual dissection) for non-invasive examination of the femoropelvic musculoskeletal anatomy in Pan troglodytes, P. paniscus, Gorilla gorilla, Pongo pygmaeus, and Homo sapiens. Specifically, we analyze the topographic relationship between muscle attachment sites and surface structures of the proximal femoral shaft such as the lateral spiral pilaster. Our results show that the origin of the vastus lateralis muscle is anterior to the insertion of gluteus maximus in all examined great ape specimens and humans. In gorillas and orangutans, the insertion of gluteus maximus is on the inferior (anterolateral) side of the lateral spiral pilaster. In chimpanzees, however, the maximus insertion is on its superior (posteromedial) side, similar to the situation in modern humans. These findings support the hypothesis that chimpanzees and humans exhibit a shared-derived musculoskeletal topography of the proximal femoral region, irrespective of their different locomotor modes, whereas gorillas and orangutans represent the primitive condition. Caution is thus warranted when inferring locomotor behavior from the surface topography of the proximal femur of fossil hominins, as the morphology of this region may contain a strong phyletic signal that tends to blur locomotor adaptation.

A bidirectional interface growth model for cranial interosseous suture morphogenesis

Interosseous sutures exhibit highly variable patterns of interdigitation and corrugation. Recent research has identified fundamental molecular mechanisms of suture formation, and computer models have been used to simulate suture morphogenesis. However, the role of bone strain in the development of complex sutures is largely unknown, and measuring suture morphologies beyond the evaluation of fractal dimensions remains a challenge. Here we propose a morphogenetic model of suture formation, which is based on the paradigm of Laplacian interface growth. Computer simulations of suture morphogenesis under various boundary conditions generate a wide variety of synthetic sutural forms. Their morphologies are quantified with a combination of Fourier analysis and principal components analysis, and compared with natural morphological variation in an ontogenetic sample of human interparietal suture lines. Morphometric analyses indicate that natural sutural shapes exhibit a complex distribution in morphospace. The distribution of synthetic sutures closely matches the natural distribution. In both natural and synthetic systems, sutural complexity increases during morphogenesis. Exploration of the parameter space of the simulation system indicates that variation in strain and/or morphogen sensitivity and viscosity of sutural tissue may be key factors in generating the large variability of natural suture complexity.

First evidence of a bipartite medial cuneiform in the hominin fossil record: a case report from the Early Pleistocene site of Dmanisi

A medial cuneiform exhibiting complete bipartition was discovered at the Early Pleistocene site of Dmanisi, Georgia. The specimen is the oldest known instance of this anatomical variant in the hominin fossil record. Here we compare developmental variation of the medial cuneiform in fossil hominins, extant humans and great apes, and discuss potential implications of bipartition for hominin foot phylogeny and function. Complete bipartition is rare among modern humans (< 1%); incomplete bipartition was found in 2 of 200 examined great ape specimens and also appears in the form of a divided distal articular surface in the Stw573c Australopithecus africanus specimen. Although various developmental pathways lead to medial cuneiform bipartition, it appears that the bipartite bone does not deviate significantly from normal overall morphology. Together, these data indicate that bipartition represents a phyletically old developmental variant of the medial cuneiform, which does not, however, affect the species-specific morphology and function of this bone.

Three-dimensional geometric morphometrics for studying floral shape variation

Variation in floral shape is of major interest to evolutionary and pollination biologists, plant systematists and developmental geneticists. Quantifying this variation has been difficult due to the three-dimensional (3D) complexity of angiosperm flowers. By combining 3D geometric representations of flowers obtained by micro-computed tomography scanning with geometric morphometric methods, well established in zoology and anthropology, floral shape variation can be analyzed quantitatively, allowing for powerful interpretation and visualization of the resulting patterns of variation.

The face of Siamopithecus: new geometric-morphometric evidence for its anthropoid status

Amphipithecids assume a key position in early primate evolution in Asia. Here we report on new maxillofacial and associated mandibular remains of Siamopithecus eocaenus, an amphipithecid primate from the Late Eocene of Krabi (Thailand) that currently represents the most complete specimen belonging to this group. We used synchrotron microtomography and techniques of virtual reconstruction to recover the three-dimensional morphology of the specimen. Geometric-morphometric analysis of the reconstructed specimen within a comparative sample of recent and fossil primates clearly associates Siamopithecus with the anthropoids. Like modern anthropoids, Siamopithecus displays a relatively short face and highly convergent and frontated orbits, the lower rim of which lies well above the alveolar plane. The cooccurrence of spatially correlated anthropoid features and classical anthropoid dental characters in one individual represents a strong argument to support the anthropoid status of Siamopithecus. It is, thus, highly unlikely that amphipithecids are specialized adapiforms exhibiting complete convergence with anthropoids.

New insights into mid-late Pleistocene fossil hominin paranasal sinus morphology

Mid-late Pleistocene fossil hominins such as Homo neanderthalensis and H. heidelbergensis are often described as having extensively pneumatized crania compared with modern humans. However, the significance of pneumatization in recognizing patterns of phyletic diversification and/or functional specialization has remained controversial. Here, we test the null hypothesis that the paranasal sinuses of fossil and extant humans and great apes can be understood as biological spandrels, i.e., their morphology reflects evolutionary, developmental, and functional constraints imposed onto the surrounding bones. Morphological description of well-preserved mid-late Pleistocene hominin specimens are contrasted with our comparative sample of modern humans and great apes. Results from a geometric morphometric analysis of the correlation between paranasal sinus and cranial dimensions show that the spandrel hypothesis cannot be refuted. However, visualizing specific features of the paranasal sinus system with methods of biomedical imaging and computer graphics reveals new aspects of patterns of growth and development of fossil hominins.

Postcranial evidence from early Homo from Dmanisi, Georgia

The Plio-Pleistocene site of Dmanisi, Georgia, has yielded a rich fossil and archaeological record documenting an early presence of the genus Homo outside Africa. Although the craniomandibular morphology of early Homo is well known as a result of finds from Dmanisi and African localities, data about its postcranial morphology are still relatively scarce. Here we describe newly excavated postcranial material from Dmanisi comprising a partial skeleton of an adolescent individual, associated with skull D2700/D2735, and the remains from three adult individuals. This material shows that the postcranial anatomy of the Dmanisi hominins has a surprising mosaic of primitive and derived features. The primitive features include a small body size, a low encephalization quotient and absence of humeral torsion; the derived features include modern-human-like body proportions and lower limb morphology indicative of the capability for long-distance travel. Thus, the earliest known hominins to have lived outside of Africa in the temperate zones of Eurasia did not yet display the full set of derived skeletal features.

Peştera cu Oase 2 and the cranial morphology of early modern Europeans

Between 2003 and 2005, the Peştera cu Oase, Romania yielded a largely complete early modern human cranium, Oase 2, scattered on the surface of a Late Pleistocene hydraulically displaced bone bed containing principally the remains of Ursus spelaeus. Multiple lines of evidence indicate an age of approximately 40.5 thousand calendar years before the present (approximately 35 ka 14C B.P.). Morphological comparison of the adolescent Oase 2 cranium to relevant Late Pleistocene human samples documents a suite of derived modern human and/or non-Neandertal features, including absence of a supraorbital torus, subrectangular orbits, prominent canine fossae, narrow nasal aperture, level nasal floor, angled and anteriorly oriented zygomatic bones, a high neurocranium with prominent parietal bosses and marked sagittal parietal curvature, superiorly positioned temporal zygomatic root, vertical auditory porous, laterally bulbous mastoid processes, superiorly positioned posterior semicircular canal, absence of a nuchal torus and a suprainiac fossa, and a small occipital bun. However, these features are associated with an exceptionally flat frontal arc, a moderately large juxtamastoid eminence, extremely large molars that become progressively larger distally, complex occlusal morphology of the upper third molar, and relatively anteriorly positioned zygomatic arches. Moreover, the featureless occipital region and small mastoid process are at variance with the large facial skeleton and dentition. This unusual mosaic in Oase 2, some of which is paralleled in the Oase 1 mandible, indicates both complex population dynamics as modern humans dispersed into Europe and significant ongoing human evolution once modern humans were established within Europe.

A fourth hominin skull from Dmanisi, Georgia

Newly discovered Homo remains, stone artifacts, and animal fossils from Dmanisi, Republic of Georgia, provide a basis for better understanding patterns of hominin evolution and behavior in Eurasia ca. 1.77 million years ago. Here we describe a fourth skull that is nearly complete, lacking all but one of its teeth at the time of death. Both the maxillae and the mandible exhibit extensive bone loss due to resorption. This individual is similar to others from the site but supplies information about variation in brain size and craniofacial anatomy within the Dmanisi paleodeme. Although this assemblage presents numerous primitive characters, the Dmanisi skulls are best accommodated within the species H. erectus. On anatomical grounds, it is argued that the relatively small-brained and lightly built Dmanisi hominins may be ancestral to African and Far Eastern branches of H. erectus showing more derived morphology.

New material of the earliest hominid from the Upper Miocene of Chad

Discoveries in Chad by the Mission Paleoanthropologique Franco-Tchadienne have substantially changed our understanding of early human evolution in Africa. In particular, the TM 266 locality in the Toros-Menalla fossiliferous area yielded a nearly complete cranium (TM 266-01-60-1), a mandible, and several isolated teeth assigned to Sahelanthropus tchadensis and biochronologically dated to the late Miocene epoch (about 7 million years ago). Despite the relative completeness of the TM 266 cranium, there has been some controversy about its morphology and its status in the hominid clade. Here we describe new dental and mandibular specimens from three Toros-Menalla (Chad) fossiliferous localities (TM 247, TM 266 and TM 292) of the same age. This new material, including a lower canine consistent with a non-honing C/P3 complex, post-canine teeth with primitive root morphology and intermediate radial enamel thickness, is attributed to S. tchadensis. It expands the hypodigm of the species and provides additional anatomical characters that confirm the morphological differences between S. tchadensis and African apes. S. tchadensis presents several key derived features consistent with its position in the hominid clade close to the last common ancestor of chimpanzees and humans.

Anthropology: the earliest toothless hominin skull

The site of Dmanisi in the Eurasian republic of Georgia has yielded striking hominin, faunal and archaeological material as evidence for the presence of early Homo outside Africa 1.77 million years ago, documenting an important episode in human evolution. Here we describe a beautifully preserved skull and jawbone from a Dmanisi hominin of this period who had lost all but one tooth several years before death. This specimen not only represents the earliest case of severe masticatory impairment in the hominin fossil record to be discovered so far, but also raises questions about alternative subsistence strategies in early Homo.

Virtual cranial reconstruction of Sahelanthropus tchadensis

Previous research in Chad at the Toros-Menalla 266 fossiliferous locality (about 7 million years old) uncovered a nearly complete cranium (TM 266-01-60-1), three mandibular fragments and several isolated teeth attributed to Sahelanthropus tchadensis. Of this material, the cranium is especially important for testing hypotheses about the systematics and behavioural characteristics of this species, but is partly distorted from fracturing, displacement and plastic deformation. Here we present a detailed virtual reconstruction of the TM 266 cranium that corrects these distortions. The reconstruction confirms that S. tchadensis is a hominid and is not more closely related to the African great apes. Analysis of the basicranium further indicates that S. tchadensis might have been an upright biped, suggesting that bipedalism was present in the earliest known hominids, and probably arose soon after the divergence of the chimpanzee and human lineages.

Evidence for interpersonal violence in the St. Cesaire Neanderthal

The St. Césaire 1 Neanderthal skeleton of a young adult individual is unique in its association with Châtelperronian artifacts from a level dated to ca. 36,000 years ago. Computer-tomographic imaging and computer-assisted reconstruction of the skull revealed a healed fracture in the cranial vault. When paleopathological and forensic diagnostic standards are applied, the bony scar bears direct evidence for the impact of a sharp implement, which was presumably directed toward the individual during an act of interpersonal violence. These findings add to the evidence that Neanderthals used implements not only for hunting and food processing, but also in other behavioral contexts. It is hypothesized that the high intra-group damage potential inherent to weapons might have represented a major factor during the evolution of hominid social behavior.

Visualizing patterns of craniofacial shape variation in Homo sapiens

The geometric morphometric analysis of shape variation in complex biological structures such as the human skull poses a number of specific challenges: the registration of homologous morphologies, the treatment of bilateral symmetry, the graphical representation of form variability in three dimensions and the interpretation of the results in terms of differential growth processes. To visualize complex patterns of shape change, we propose an alternative to classical Cartesian deformation grids in the style of D'Arcy W. Thompson. Reference to the surface structures of the organism under investigation permits a comprehensive visual grasp of shape change and its tentative interpretation in terms of differential growth. The application of this method to the analysis of human craniofacial shape variation reveals distinct modes of growth and development of the neurocranial and viscerocranial regions of the skull. Our data further indicate that variations in the orientation of the viscerocranium relative to the neurocranium impinge on the shapes of the face and the cranial vault.