Protective buttressing of the hominin face

When humans fight hand‐to‐hand the face is usually the primary target and the bones that suffer the highest rates of fracture are the parts of the skull that exhibit the greatest increase in robusticity during the evolution of basal hominins. These bones are also the most sexually dimorphic parts of the skull in both australopiths and humans. In this review, we suggest that many of the facial features that characterize early hominins evolved to protect the face from injury during fighting with fists. Specifically, the trend towards a more orthognathic face; the bunodont form and expansion of the postcanine teeth; the increased robusticity of the orbit; the increased robusticity of the masticatory system, including the mandibular corpus and condyle, zygoma, and anterior pillars of the maxilla; and the enlarged jaw adductor musculature are traits that may represent protective buttressing of the face. If the protective buttressing hypothesis is correct, the primary differences in the face of robust versus gracile australopiths may be more a function of differences in mating system than differences in diet as is generally assumed. In this scenario, the evolution of reduced facial robusticity in Homo is associated with the evolution of reduced strength of the upper body and, therefore, with reduced striking power. The protective buttressing hypothesis provides a functional explanation for the puzzling observation that although humans do not fight by biting our species exhibits pronounced sexual dimorphism in the strength and power of the jaw and neck musculature. The protective buttressing hypothesis is also consistent with observations that modern humans can accurately assess a male's strength and fighting ability from facial shape and voice quality.     

Habitual throwing and swimming correspond with upper limb diaphyseal strength and shape in modern human athletes

Variation in upper limb long bone cross‐sectional properties may reflect a phenotypically plastic response to habitual loading patterns. Structural differences between limb bones have often been used to infer past behavior from hominin remains; however, few studies have examined direct relationships between behavioral differences and bone structure in humans. To help address this, cross‐sectional images (50% length) of the humeri and ulnae of university varsity‐level swimmers, cricketers, and controls were captured using peripheral quantitative computed tomography. High levels of humeral robusticity were found in the dominant arms of cricketers, and bilaterally among swimmers, whereas the most gracile humeri were found in both arms of controls, and the nondominant arms of cricketers. In addition, the dominant humeri of cricketers were more circular than controls. The highest levels of ulnar robusticity were also found in the dominant arm of cricketers, and bilaterally amongst swimmers. Bilateral asymmetry in humeral rigidity among cricketers was greater than swimmers and controls, while asymmetry for ulnar rigidity was greater in cricketers than controls. The results suggest that more mechanically loaded upper limb elements––unilaterally or bilaterally––are strengthened relative to less mechanically loaded elements, and that differences in mechanical loading may have a more significant effect on proximal compared to distal limb segments. The more circular humerus in the dominant arm in cricketers may be an adaptation to torsional strain associated with throwing activities. The reported correspondence between habitual activity patterns and upper limb diaphyseal properties may inform future behavioral interpretations involving hominin skeletal remains. Am J Phys Anthropol 2009. © 2009 Wiley‐Liss, Inc.     

Robusticity and sexual dimorphism in the postcranium of modern hunter-gatherers from Australia

Throughout much of prehistory, humans practiced a hunting and gathering subsistence strategy. Elevated postcranial robusticity and sexually dimorphic mobility patterns are presumed consequences of this strategy, in which males are attributed greater robusticity and mobility than females. Much of the basis for these trends originates from populations where skeletal correlates of activity patterns are known (e.g., cross-sectional geometric properties of long bones), but in which activity patterns are inferred using evidence such as archaeological records (e.g., Pleistocene Europe). Australian hunter-gatherers provide an opportunity to critically assess these ideas since ethnographic documentation of their activity patterns is available. We address the following questions: do skeletal indicators of Australian hunter-gatherers express elevated postcranial robusticity and sexually dimorphic mobility relative to populations from similar latitudes, and do ethnographic accounts support these findings. Using computed tomography, cross-sectional images were obtained from 149 skeletal elements including humeri, radii, ulnae, femora, and tibiae. Cross-sectional geometric properties were calculated from image data and standardized for body size. Australian hunter-gatherers often have reduced robusticity at femoral and humeral midshafts relative to forager (Khoi-San), agricultural/industrialized (Zulu), and industrialized (African American) groups. Australian hunter-gatherers display more sexual dimorphism in upper limb robusticity than lower limb robusticity. Attributing specific behavioral causes to upper limb sexual dimorphism is premature, although ethnographic accounts support sex-specific differences in tool use. Virtually absent sexual dimorphism in lower limb robusticity is consistent with ethnographic accounts of equivalently high mobility among females and males. Thus, elevated postcranial robusticity and sexually dimorphic mobility do not always characterize hunter-gatherers.     

Hunter-gatherer postcranial robusticity relative to patterns of mobility, climatic adaptation, and selection for tissue economy

Human skeletal robusticity is influenced by a number of factors, including habitual behavior, climate, and physique. Conflicting evidence as to the relative importance of these factors complicates our ability to interpret variation in robusticity in the past. It remains unclear how the pattern of robusticity in the skeleton relates to adaptive constraints on skeletal morphology. This study investigates variation in robusticity in claviculae, humeri, ulnae, femora, and tibiae among human foragers, relative to climate and habitual behavior. Cross-sectional geometric properties of the diaphyses are compared among hunter-gatherers from southern Africa (n = 83), the Andaman Islands (n = 32), Tierra del Fuego (n = 34), and the Great Lakes region (n = 15). The robusticity of both proximal and distal limb segments correlates negatively with climate and positively with patterns of terrestrial and marine mobility among these groups. However, the relative correspondence between robusticity and these factors varies throughout the body. In the lower limb, partial correlations between polar second moment of area (J(0.73)) and climate decrease from proximal to distal section locations, while this relationship increases from proximal to distal in the upper limb. Patterns of correlation between robusticity and mobility, either terrestrial or marine, generally increase from proximal to distal in the lower and upper limbs, respectively. This suggests that there may be a stronger relationship between observed patterns of diaphyseal hypertrophy and behavioral differences between populations in distal elements. Despite this trend, strength circularity indices at the femoral midshaft show the strongest correspondence with terrestrial mobility, particularly among males.     

Neandertal energetics and foraging efficiency

Mechanical interpretations of Neandertal skeletal robusticity suggest extremely high activity levels compared to modern humans. Such activity patterns imply high energy requirements; yet it has been argued that Neandertals were also inefficient foragers. The present study addresses this apparent conflict by estimating energy needs in Neandertals and then evaluating those estimates in the context of energetic and foraging data compiled for contemporary human foragers and nonhuman primates. Energy demands for Neandertals were determined by first predicting basal metabolic rates (BMR) from body weight estimates using human standards developed by the World Health Organization [FAO/WHO/UNU (1985) Energy and Protein Requirements. Report of the Joint FAO/WHO/UNU Export Committee, Geneva: WHO]. Total daily energy expenditure (kcal/day) was then estimated assuming high levels of physical activity (i.e., 2--3 x BMR), comparable to those observed among subsistence-level populations today. These estimates of energy requirements (ranging from 3000--5500 kcal/day) were then used to determine Neandertal foraging efficiency assuming (1) minimal survival-level foraging returns, and (2) daily foraging times longer than those observed among any contemporary foraging group and comparable to a nonhuman primate. Even with these extremely conservative parameters, estimates of Neandertal foraging efficiency (approximately 800--1150 kcal/h foraged) were comparable to those observed among living hunter-gatherers. These results indicate that if Neandertals did have heavy activity levels, as implied by their skeletal robusticity, they would have required foraging efficiencies within the range observed among modern groups. Thus, Neandertals could have been either highly active or poor foragers, but they could not have been both.     

Virtual reconstruction of the Neandertal lower limbs with an estimation of hamstring muscle moment arms

A major problem of fossil hominid analysis is a lack of complete specimens. Many individual specimens have been damaged by the effects of diagenesis and excavation. Significant advances in the field of three dimensional image processing (3D) have enabled the creation of accurately scaled reconstructions of individual fossil bones using mirrored parts of the same fossil bone or human/fossil hominid equivalents. This study presents, for the first time, a method to reconstruct a 3D virtual model of the lower limb of the Neandertal using different bones from different fossil remains (Spy II, Neandertal 1 and Kebara 2) and integrating them into a single model of the Neandertal lower limb. A biomechanical analysis of the model was performed, including computer graphics visualization of the results, motion displacement graphs and muscle moment arms. The overall method has been implemented into an open-source customized software (lhpFusionBox) developed for the biomechanical study of the musculoskeletal system.     

Endocrine control of skeletal robusticity.

Changes of skeletal robusticity result from a mosaic response of various parts of the skeleton to given endocrine changes. The character of these reactions corresponds to that of muscles which act as selective target areas for specific hormones. Robusticity changes are mediated by increases or decreases of the length and weight of the bones. The changes are probably species- or even subspecies-specific.     

The anomalous archaic Homo femur from Berg Aukas, Namibia: a biomechanical assessment.

The probably Middle Pleistocene human femur from Berg Aukas, Namibia, when oriented anatomically and analyzed biomechanically, presents an unusual combination of morphological features compared to other Pleistocene Homo femora. Its midshaft diaphyseal shape is similar to most other archaic Homo, but its subtrochanteric shape aligns it most closely with earlier equatorial Homo femora. It has an unusually low neck shaft angle. Its relative femoral head size is matched only by Neandertals with stocky hyperarctic body proportions. Its diaphyseal robusticity is modest for a Neandertal, but reasonable compared to equatorial archaic Homo femora. Its gluteal tuberosity is relatively small. Given its derivation from a warm climatic region, it is best interpreted as having had relatively linear body proportions (affecting proximal diaphyseal proportions, shaft robusticity, and gluteal tuberosity size) combined with an elevated level of lower limb loading during development (affecting femoral head size and neck shaft angle).     

F-81 skeleton from Wadi Mataha, Jordan, and its bearing on human variability in the Epipaleolithic of the Levant

The discovery of a Middle Epipaleolithic adult skeleton (F-81) at the site of Wadi Mataha in southern Jordan provides new insights into human variability in the Epipaleolithic of the Levant. This paper analyzes the skeletal morphology of Wadi Mataha F-81 in the context of other Epipaleolithic remains from Jordan and Israel to assess the current evidence for morphological variability throughout this period. The F-81 skeleton shares morphological features with earlier Epipaleolithic skeletons from Ohalo and Nahal Ein Gev, and later Natufian populations. Despite the morphological similarities, F-81 extends the range of known variability prior to the Natufian with its unusually small stature and unique combination of morphological characteristics. High levels of cranial and postcranial robusticity suggest that the F-81 individual was physically active and terrestrially mobile. Pronounced bilateral asymmetry in the upper limb suggests significant lateralization of habitual activity. In the context of Epipaleolithic remains, the F-81 skeleton provides preliminary evidence for greater morphological variability, terrestrial mobility, and lateralized habitual behavior prior to the Natufian, and skeletal gracilization between the Middle and Late Epipaleolithic in the Levant.     

Sexual dimorphism in relation to big-game hunting and economy in modern human populations

Postcranial skeletal data from two recent Eskimo populations are used to test David Frayer's model of sexual dimorphism reduction in Europe between the Upper Paleolithic and Mesolithic. Frayer argued that a change from big-game hunting and adoption of new technology in the Mesolithic reduced selection for large body size in males and led to a reduction in skeletal sexual dimorphism. Though aspects of Frayer's work have been criticized in the literature, the association of big-game hunting and high sexual dimorphism is untested. This study employs univariate and multivariate analysis to test that association by examining sexual dimorphism of cranial and postcranial bones of two recent Alaskan Eskimo populations, one being big-game (whale and other large marine mammal) hunting people, and the second being salmon fishing, riverine people. While big-game hunting influences skeletal robusticity, it cannot be said to lead to greater sexual dimorphism generally. The two populations had different relative sexual dimorphism levels for different parts of the body. Notably, the big-game hunting (whaling) Eskimos had the lower multivariate dimorphism in the humerus, which could be expected to be the structure under greatest exertion by such hunting in males. While the exertions of the whale hunting economic activities led to high skeletal robusticity, as predicted by Frayer's model, this was true of the females as well as the males, resulting in low sexual dimorphism in some features. Females are half the sexual dimorphism equation, and they cannot be seen as constants in any model of economic behavior. © 1993 Wiley-Liss, Inc.     

A modern human humerus from the early aurignacian of Vogelherdhöhle (Stetten, Germany)

Implicit in much of the discussion of the cultural and population biological dynamics of modern human origins in Europe is the assumption that the Aurignacian, from its very start, was made by fully modern humans. The veracity of this assumption has been challenged in recent years by the association of Neandertal skeletal remains with a possibly Aurignacian assemblage at Vindija Cave (Croatia) and the association of Neandertals with distinctly Upper Paleolithic (but non-Aurignacian) assemblages at Arcy-sur-Cure and St. C?esaire (France). Ideally we need human fossil material that can be confidently assigned to the early Aurignacian to resolve this issue, yet in reality there is a paucity of well-provenanced human fossils from early Upper Paleolithic contexts. One specimen, a right humerus from the site of Vogelherd (Germany), has been argued, based on its size, robusticity, and muscularity, to possibly represent a Neandertal in an Aurignacian context. The morphological affinities of the Vogelherd humerus were explored by univariate and multivariate comparisons of humeral epiphyseal and diaphyseal shape and strength measures relative to humeri of Neandertals and Early Upper Paleolithic (later Aurignacian and Gravettian) modern humans. On the basis of diaphyseal cross-sectional geometry, deltoid tuberosity morphology, and distal epiphyseal morphology, the specimen falls clearly and consistently with European early modern humans and not with Neandertals. Along with the other Vogelherd human remains, the Vogelherd humerus represents an unequivocal association between the Aurignacian and modern human morphology in Europe.     

Paleopathological Study of Dwarfism-Related Skeletal Dysplasia in a Late Joseon Dynasty (South Korean) Population

Skeletal dysplasias related to genetic etiologies have rarely been reported for past populations. This report presents the skeletal characteristics of an individual with dwarfism-related skeletal dysplasia from South Korea. To assess abnormal deformities, morphological features, metric data, and computed tomography scans are analyzed. Differential diagnoses include achondroplasia or hypochondroplasia, chondrodysplasia, multiple epiphyseal dysplasia, thalassemia-related hemolytic anemia, and lysosomal storage disease. The diffused deformities in the upper-limb bones and several coarsened features of the craniofacial bones indicate the most likely diagnosis to have been a certain type of lysosomal storage disease. The skeletal remains of EP-III-4-No.107 from the Eunpyeong site, although incomplete and fragmented, provide important clues to the paleopathological diagnosis of skeletal dysplasias.     

Brief communication: A morphometric analysis of the neandertal upper second molar leuca I

The scarcity of Neandertal remains from Southern Europe hampers our understanding of Neandertal variability, and can bias interpretations about Neandertal geographic variation. To address this issue, it is often important to reassess human remains that, while discovered decades ago, remain relatively unknown to the scientific community. In this contribution, we provide a complete state‐of‐the‐art comparative morphometric analysis of Leuca I, an unworn left second upper molar (LM²) discovered in 1958 in Bambino's Cave (near Santa Maria di Leuca, Apulia, Italy) and attributed to Homo neanderthalensis. Our study includes comparisons of standard metric and nonmetric data, a 2D image analysis of the occlusal surface and measurements of both 2D and 3D enamel thickness and dental tissue proportions. Although Leuca I follows the Neandertal M²s trend in some morphometric aspects (i.e., small relative occlusal polygon area), in other cases it falls to the higher end (for 3D average enamel thickness) or even outside (for 3D‐relative enamel thickness) the Neandertal M² variability, thus increasing the known Neandertal range of variation. Am J Phys Anthropol 152:300–305, 2013. © 2013 Wiley Periodicals, Inc.     

Robusticity and osteoarthritis at the trapeziometacarpal joint in a Bronze Age population from Tell Abraq, United Arab Emirates

Osteoarthritis (OA) is a progressive disease of the joints and can cause pain, reduced range of motion and strength, and ultimately loss of function at affected joints. Osteoarthritis often occurs at sites where biomechanical stress is acutely severe or moderate but habitual over the course of a lifetime. Skeletal remains from an Umm an-Nar tomb at Tell Abraq, United Arab Emirates (ca. 2300 BC), were recovered and represented over 300 individuals of all ages. The remains were disarticulated, commingled, and mostly fragmented. An analysis of 650 well-preserved adult metacarpal and carpal bones, from the tomb's western chamber, revealed that over 53% of the trapeziometacarpal joint facets showed signs of OA varying from mild to severe. The first and second metacarpals and trapezium bones were sided and evaluated for OA at the trapeziometacarpal joint articulations. Osteoarthritis was detected on 53% of the first metacarpals, 40% of the second metacarpals, and 57% of the trapezium bones. All specimens appeared enlarged, and the first metacarpals were assessed for sexual identification and robusticity. Eighty-five percent of the bones were probable males, and more than 80% of them had a robusticity index of 60 or higher. A strong correlation was found between OA, sex, and robusticity. High levels of OA and robusticity at the thumb suggest that the people of Tell Abraq were habitually involved in biomechanically challenging work with their hands.     

Mechanical determinants of bone form: insights from skeletal remains

Analysis of skeletal remains from humans living in the past forms an important complement to observational and experimental studies of living humans and animal models. Including earlier humans in such analyses increases the range of variation in both behavior and body size and shape that are represented, and can provide insights into the adaptive potential of the modern human skeleton. I review here a variety of studies of archaeological and paleontological remains that have investigated differences in skeletal structure from a mechanical perspective, focusing in particular on diaphyseal strength of the limb bones. Several conclusions can be drawn from these studies: 1) there has been a decline in overall skeletal strength relative to body size over the course of human evolution that has become progressively steeper in recent millennia, probably due to increased sedentism and technological advancement; 2) differences in pelvic structure and hip mechanical loadings affect femoral shape; 3) activity patterns affect overall strength and shape of both the lower and upper limb bones; and 4) responsiveness to changes in mechanical loading varies between skeletal features (e.g., articulations versus diaphyses) and by age.     

The Pech-de-l'Azé I Neandertal child: ESR, uranium-series, and AMS 14C dating of its MTA type B context

The Pech-de-l'Azé I skull and mandible are included in the juvenile Neandertal remains from Europe. However, some preserved features in the cranial skeleton seem to distinguish the specimen from other Neandertal children. Unfortunately, the stratigraphic position and dating of this child has never been clear. Our recent work on unpublished archives show that the Pech-de-l'Azé I Neandertal child was discovered at the bottom of layer 6, attributed to the Mousterian of Acheulean tradition type B. These skull and mandible are the first diagnostic human remains (aside from an isolated tooth) attributed to the Mousterian of Acheulian tradition (MTA) type B. Consequently, we confirm that Neandertals were the makers of this Mousterian industry, which is characterized by unusual high frequencies of Upper Paleolithic type tools, elongated blanks and blades. We were able to date the context of the hominid remains by dating layer 6 and the layers above and beneath it using ESR, coupled ESR/(230)Th/(234)U (coupled ESR/U-series), and AMS (14)C. Coupled ESR/U-series results on 16 mammalian teeth constrain the age of the uppermost layer 7 to 41-58ka, and layer 6 to 37-51ka. The wide spread in each age estimate results mainly from uncertainties in the gamma-dose rate. These ages are concordant with AMS (14)C ages of two bones coming from the top of layer 6, which provide dates of about 41.7-43.6ka cal BP. A combination of stratigraphic arguments and dating results for layers 6 and 7 show that the Neandertal child cannot be older than 51ka or younger than 41ka. The lowermost layer 4 is shown to be older than 43ka by the principle of superposition and ESR dating in the immediately overlying layer 5. This study shows that the MTA type B had been manufactured by Neandertals before the arrival of anatomically modern humans in the local region. Additionally, by providing a firm chronological framework for the specific morphometric the features of Pech-de-l'Azé I Neandertal child, this study is a new step toward the understanding of temporal and spatial changes in the ontogenesis of Neandertals in south-western Europe during oxygen isotope stages 5-3.     

Osteoarchaeological evidence for leprosy from western Central Asia

Published reports of palaeopathological analyses of skeletal collections from Central Asia are, to date, scarce. During the macroscopic examination of skeletal remains dating to the early first millennium AD from the Ustyurt Plateau, Uzbekistan, diagnostic features suggestive of leprosy were found on one individual from Devkesken 6. This adult female exhibited rhinomaxillary changes indicative of leprosy: resorption of the anterior nasal spine, rounding and widening of the nasal aperture, erosion of the alveolar margin, loss of a maxillary incisor, and inflammatory changes in the hard palate. While it is unclear whether the bones of the hands and the feet from this individual were absent as a result of collection strategy or poor preservation, lesions affecting the tibia and fibula were recorded, and the ways in which they may be related to a diagnosis of leprosy are discussed. This is the first skeletal evidence of leprosy from Central Asia and raises questions not only about the spread of the disease in the past, but also about the living conditions of what traditionally were thought of as nomadic peoples.     

The ontogeny of Holocene and Late Pleistocene human postcranial strength

While a wide variety of studies have focused on population variation in adult cross‐sectional properties, relatively little is known about population variation in postcranial robusticity in immature individuals. Furthermore, the age at which the population differences readily detected in adults manifest during growth is also unknown. This research addresses these gaps in our current understanding through the analysis of immature humeral and femoral long bone strength. Cross‐sectional geometry was used to compare the developmental trajectories of diaphyseal strength in Late Pleistocene Neandertal and modern human subadults to a sample of immature humans from seven geographically diverse Holocene populations. Population differences in size‐standardized cross‐sectional properties appear to be systemic and develop very early in ontogeny in the Holocene sample. In many cases, these differences are present before one year of age. In general, the Late Pleistocene fossil samples fit within the range of recent human variation in long bone strength. Population differences detected here are likely related to a combination of factors including activity patterns, genetic propensities, and nutritional status. These results highlight the complex mosaic of processes that result in adult postcranial robusticity, and suggest that further exploration of the developmental interplay between intrinsic and extrinsic influences on skeletal robusticity will likely enhance our understanding of adult postcranial morphology. Am J Phys Anthropol 2010. © 2009 Wiley‐Liss, Inc.     

Developmental stress and cranial hypostosis by epigenetic trait occurrence and distribution: an exploratory study on the Italian Neandertals

The occurrence and distribution of 35 cranial epigenetic traits in the Italian Neandertals (Saccopastore 1 and 2, Guattari 1) were examined according to morpho-functional cranial regions and with respect to a distinction between hypostosis (i.e., weak osseous development, arrested morphogenesis, retention of infantile features) and hyperostosis (i.e. excess of ossification, not reaching the pathological condition). The results, expressed ashypostotic scores, showed higher levels of hypostosis in these Neandertal specimens than in recent European samples. The highest expressions of hypostotis were observed in those regions of the Neandertal cranium where disequilibrium between skeletal and cerebral growth factors was expected. These results—interpreted as expression of developmental stress—are consistent with a heterochronic interpretation of the development of the Neandertal cranium; namely, a faster ossification of the cranial vault relative to brain growth rates.