辽宁建平古人类肱骨形态结构分析

1957年,在辽宁省建平县发现了一根古人类肱骨化石,编号PA103。通过同一批龙骨中筛选的哺乳动物化石,吴汝康推断PA103应该为更新世晚期古人类,并对该化石进行了表面形态特征观察和描述。为了对PA103化石的内外结构进行更全面的了解,除了线性测量数据的对比,本文还通过计算机断层扫描技术,结合生物力学和形态示量图分析对建平古人类右侧肱骨化石PA103进行了分析。通过本研究发现,PA103骨干横断面的生物力学粗壮度和力学形状指数明显小于尼安德特人,而与同时期欧亚大陆古人类不利手侧最为接近,这说明建平人右侧肱骨可能不是惯用手,同时,建平人的行为活动应该与同时期同地区的古人类处于同一水平,而小于尼安德特人。整体来看,PA103骨干骨密质厚度和截面惯性矩与近现代人的分布模式较为接近,除局部数值增大外,其整体数值小于近现代人的平均水平,这可能与遗传或行为活动有关,由于缺少古人类化石对比数据,更详细的了解还需后期开展更多相关的研究。     

Incus facet morphology in carnivorous mammals from different ecosystems: Taxonomy vs. habitat

This study is prompted by the discovery of an incus of Hyaenodon, the first known auditory ossicle of this genus and thus of any hyaenodont mammal so far. A large set of incudes of recent Carnivora, including felids, hyaenids, viverrids, herpestids, nandiniid and canids of different ecosystems, was set up for morphological comparison. This study examines especially the incudo-mallear facet. Typically, the incudo-mallear facet is composed of: (1) three articular surfaces in felids, (2) a U-shaped surface in hyaenids and (3) four surfaces in canids. Both taxonomy (on family level) and habitat (open, closed or mixed habitat preference) might have an impact on the morphology of the incus facets, the former having a major impact in our sample. The Hyaenodon incus is small, delicate and possesses an incudo-mallear facet of a general saddle-shape with two articulation facets, a large superior articulation area and a circular, inferior articulation area. Herein, its general morphology and facet shape is most similar to the felid incus morphology.     

Neandertal postcranial remains from the Sima de las Palomas del Cabezo Gordo, Murcia, southeastern Spain

The Sima de las Palomas, southeastern Spain, has yielded a series of Neandertal postcranial remains, including immature and mature isolated elements and the fragmentary partial skeleton of a young adult (Palomas 92). The remains largely conform to the general late archaic/Neandertal morphological pattern in terms of humeral diaphyseal shape, pectoralis major tuberosity size and pillar thickness, ulnar coronoid process height, manual middle phalangeal epiphyseal breadth, manual distal phalangeal tuberosity shape and breadth, femoral diaphyseal shape, and probably body proportions. Palomas 92 contrasts with the Neandertals in having variably gracile hand remains, a more sellar trapezial metacarpal 1 facet, more anteroposteriorly expanded mid-proximal femoral diaphysis, and less robust pedal proximal phalanges. The Palomas Neandertals contrast with more northern European Neandertals particularly in various reflections of overall body size.     

Activity, climate, and postcranial robusticity: implications for modern human origins and scenarios of adaptive change

Postcranial robusticity--the massiveness of the skeleton--figures prominently in the debate over the origin of modern humans. Anthropologists use postcranial robusticity to infer the activity levels of prehistoric populations, and changes in robusticity are often used to support scenarios of adaptive change. These scenarios explain differences in morphology as the result of a change in lifestyle (habitual activity). One common scenario posits that early modern humans were more gracile than Neandertals because the modern humans' complex culture required less physical exertion. However, lifestyle is only one of many influences on morphology. Climate has clear correlations with physique and skeletal proportions. Analysis of recent humans that differ in terms of lifestyle and climatic adaptations reveals that limb bone robusticity varies with climate as much as or more than with lifestyle. Many of the differences in robusticity between Neandertals and early modern humans appear to be related to climatic adaptations. The results support the single-recent origin model of modern human origins. The differences in robusticity between Neandertals and early modern humans suggest that population replacement rather than local evolution best explains the emergence of modern humans in Europe. Both climatic adaptations (primarily body proportions) and lifestyle should be considered in analyses of robusticity.     

Body size, locomotion, and long bone cross-sectional geometry in indriid primates.

The geometry of the midshaft cross-sections of the femur and humerus of five indriid species was analysed. Internal (marrow cavity) and external diameters were measured on X-rays in the anteroposterior (a-p) and mediolateral (m-l) planes; cross-sectional areas, second moments of area, and section moduli were calculated using formulae for a hollow ellipse. Cortical thickness, robusticity indices (relating external diameters to the length of the bones), and a-p/m-l shape variables were also calculated. Model II regression was supplemented by analyses of correlation between size and shape. Indriids are saltatory, i.e., their locomotion is dominated by the hind limbs. Accordingly, the femur is more rigid than the humerus, and it shows a consistent difference between the a-p and m-l planes in measures related to bending strength. Cortical thickness varies considerably both within and across species. The type specimen of the new species Propithecus tattersalli is virtually indistinguishable from P. verreauxi on the basis of its long bone cross-sectional geometry. Femoral robusticity is uncorrelated with size, but humeral robusticity decreases significantly with increasing size. Femoral shape variables (a-p/m-l) are all negatively correlated with body size, indicating that m-l dimensions of the femur increase at a faster rate than do a-p dimensions. The highly loaded plane of movement seems to be more reinforced in the smaller species. Contrary to static biomechanical scaling predictions of positive allometry, all cross-sectional parameters scale relatively close to isometry. It is concluded that either changes in locomotor performance must compensate for the weight-related increase in forces and moments or that the larger-bodied animals operate appreciably closer to the limits of their safety margins.     

Hand biomechanics during simulated stone tool use

Human radial digits have derived features compared with apes, with long robust thumbs, relatively larger joint surfaces, and hypertrophic thenar muscles. Here we test the hypothesis that these features evolved in the context of making and using stone tools, specifically for producing large gripping forces and for countering large joint contact stresses. We used portable force plates simulating early stone tools to: 1) document and compare the magnitude of external/internal forces and joint stresses in the radial digits during hardhammer percussion and flake use, and 2) examine how variation in digit morphology affects muscle and joint mechanics during stone tool use. Force and kinematic data were collected from a sample representing normal variation in digit morphology (n = 25). The effects of digit size/shape on digit biomechanics were evaluated using partial correlations, controlling for tool reaction forces and impact velocities. Results show that individuals with longer digits require relatively less muscle force to stabilize digital joints, and are exposed to relatively lower joint contact stresses during stone tool use, due in part to an increase in the robusticity of metacarpals and phalanges in humans relative to chimpanzees. These analyses further suggest that Pan- or australopith-like pollical anatomy presents serious performance challenges to habitual tool use. Our data support the hypothesis that evolutionary increases in thumb length, robusticity, and thenar muscle mass enabled Homo to produce more force and to tolerate higher joint stresses during tool use.     

Obstetric implications of neanderthal robusticity and bone density

Neanderthal pelvic morphology is not well understood, despite the recent find and analysis of the Kebara 2 pelvis. Many of the proposed hypotheses focus on the possible need for a larger birth canal. A previously unexplored aspect involves possible direct obstetric implications of bone robusticity and density. These characteristics ocan affect obstetrics in modern humans, especially the molding of the neonate's head during parturition: engineering studies have shown that denser neonate cranial bones undergo less deformation, and thicker (more robust) cranial bones would also be expected to deform less during the birth process. These bone characteristics may also result in a less flexible birth canal. Thus, more robust or denser bones could result in the need for a larger birth canal or a smaller neonate head, due to decreased flexibility. Examples from modern populations are discussed and the conclusions applied to Neanderthals, who are known to have had high bone robusticity and may have had high bone density, given their heavy musculature. (A positive association between muscle mass and bone density has been observed repeatedly in modern humans.) We conclude that bone robusticity and density may have obstetrical implications for Neanderthals, with particular importance for neonate head molding during birth.     

Metacarpal proportions in Australopithecus africanus

Recent work has shown that, despite being craniodentally more derived, Australopithecus africanus had more apelike limb-size proportions than A. afarensis. Here, we test whether the A. africanus hand, as judged by metacarpal shaft and articular proportions, was similarly apelike. More specifically, did A. africanus have a short and narrow first metacarpal (MC1) relative to the other metacarpals? Proportions of both MC breadth and length were considered: the geometric mean (GM) of articular and midshaft measurements of MC1 breadth was compared to those of MC2-4, and MC1 length was compared to MC3 length individually and also to the GM of MC2 and 3 lengths. To compare the extant hominoid sample with an incomplete A. africanus fossil record (11 attributed metacarpals), a resampling procedure imposed sampling constraints on the comparative groups that produced composite intrahand ratios. Resampled ratios in the extant sample are not significantly different from actual ratios based on associated elements, demonstrating the methodological appropriateness of this technique. Australopithecus africanus metacarpals do not differ significantly from the great apes in the comparison of breadth ratios but are significantly greater than chimpanzees and orangutans in both measures of relative length. Conversely, A. africanus has a significantly smaller breadth ratio than modern humans, but does not significantly differ from this group in either measure of relative length. We conclude that the first metacarpals of A. africanus are more apelike in relative breadth while also being more humanlike in relative length, a finding consistent with previous work on A. afarensis hand proportions. This configuration would have likely promoted a high degree of manipulative dexterity, but the relatively slender, apelike first metacarpal suggests that A. africanus did not place the same mechanical demands on the thumb as more recent, stone-tool-producing hominins.     

Relationship of cranial robusticity to cranial form,geography and climate in Homo sapiens

Variation in cranial robusticity among modern human populations is widely acknowledged but not well‐understood. While the use of “robust” cranial traits in hominin systematics and phylogeny suggests that these characters are strongly heritable, this hypothesis has not been tested. Alternatively, cranial robusticity may be a response to differences in diet/mastication or it may be an adaptation to cold, harsh environments. This study quantifies the distribution of cranial robusticity in 14 geographically widespread human populations, and correlates this variation with climatic variables, neutral genetic distances, cranial size, and cranial shape. With the exception of the occipital torus region, all traits were positively correlated with each other, suggesting that they should not be treated as individual characters. While males are more robust than females within each of the populations, among the independent variables (cranial shape, size, climate, and neutral genetic distances), only shape is significantly correlated with inter‐population differences in robusticity. Two‐block partial least‐squares analysis was used to explore the relationship between cranial shape (captured by three‐dimensional landmark data) and robusticity across individuals. Weak support was found for the hypothesis that robusticity was related to mastication as the shape associated with greater robusticity was similar to that described for groups that ate harder‐to‐process diets. Specifically, crania with more prognathic faces, expanded glabellar and occipital regions, and (slightly) longer skulls were more robust than those with rounder vaults and more orthognathic faces. However, groups with more mechanically demanding diets (hunter‐gatherers) were not always more robust than groups practicing some form of agriculture. Am J Phys Anthropol, 2010. © 2009 Wiley‐Liss, Inc.     

Load-bearing role of facets in a lumbar segment under sagittal plane loadings

In the present work, the load-bearing role of the facet joints in a lumbar I2-3 segment is quantitatively determined by means of a three dimensional nonlinear finite element program. The analysis accounts for both material and geometric nonlinearities and treats the facet articulation as a nonlinear moving contact problem. The disc nucleus is considered as an inviscid incompressible fluid and the annulus as a composite of collagenous fibres embedded in a matrix of ground substance. The spinal ligaments are modelled as a collection of nonlinear axial elements. The loadings consist of axial compression and sagittal plane shears and bending moments, acting alone or combined. The results show that in pure compression, the external axial force is transmitted primarily by the intervertebral disc. The facet joints carry only a small percentage of the force. However, the facet joints carry large forces in extension, whereas in small flexion they carry none. Addition of compression tends to increase these contact forces in extension while it has no effect on them in flexion. In extension, the forces on the facet joints are transmitted by both the articular surfaces and the capsular ligaments. Although in small flexion the facets carry no load, large contact forces are predicted to develop as the segment is flexed beyond 7-8 degrees. These forces are of the same magnitude as those computed under large extension rotation and are oriented nearly in the horizontal plane with negligible component in the axial direction. The horizontal components of the contact forces generated during articulation are often larger than the axial components which directly resist the applied compressive force. The axial components of the contact forces, therefore, grossly underestimate the total forces acting on the facets. The transfer of forces from one facet to the adjacent one occurs through distinct areas in flexion and in extension loadings. That is, on the superior articular surface, the contact area shifts from the upper tip in large flexion to the lower margin in extension. On the inferior articular surface, the contact area shifts from the upper and central regions in large flexion to the lower tip in extension.     

Interspecific and intraspecific relationships between tooth size and jaw size in primates

The association between mandibular robusticity, postcanine megadontia, and canine reduction in hominins has led to speculation that large and robust jaws might be required to spatially accommodate large canine and molar teeth in hominins and other primates. If so, then variations in mandibular form that are generally regarded as biomechanical adaptations to masticatory demands might instead be incidental effects of functional requirements of tooth support. While the association between large teeth and deep, robust jaws in hominins is well known, the relationship between tooth size and jaw size has not been systematically evaluated in a comparative sample of primates. We evaluate the relationships between molar tooth size, canine tooth size, and mandibular corpus and symphyseal dimensions in a sample of adult anthropoids in interspecific (n=84 species) and intraspecific (n=36 species) contexts. For intraspecific comparisons, tooth size and jaw size are correlated, but for a majority of species this is a function of sexual size dimorphism. Interspecific comparisons lend little direct support to the hypothesis that jaw breadth directly covaries with molar tooth breadth, but they do support the hypothesis that mandibular depth is associated with canine tooth size in males. The latter observation suggests that if there is a causal association between canine size and mandibular depth, it is subject to a threshold effect. In contrast, neither corpus nor symphyseal robusticity, measured as a shape index of breadth/height, are correlated with tooth size. Our results suggest that further studies of the relationship between tooth size and corpus morphology should focus on tooth root size and corpus bony architecture, and that species-specific factors should have a strong impact on such relationships.     

Late pleistocene human femoral diaphyseal curvature

Anterior femoral curvature is a consistent characteristic of Pleistocene and recent humans, although variation exists in the degree of curvature among individuals and across populations. In particular, one group, the Neandertals, has been characterized for a century as having marked femoral curvature. To evaluate the degree of anterior femoral curvature in both Neandertals and other Late Pleistocene humans, their curvature subtenses and proximodistal positions were evaluated in the context of recent human variation. Recent human comparisons show little relationship between subtense (absolute curvature) and femoral length, suggesting that an index that incorporates subtense relative to the length of the femur is inappropriate for between-group assessments. Neandertals were statistically indistinguishable from Middle or earlier Upper Paleolithic modern humans in the degree of absolute curvature, all of whom had greater curvature on average than all later humans. Additionally, Neandertals and Qafzeh-Skhul early modern humans had a more distal point of maximum curvature than any other group. Curvature was not strongly correlated with functional considerations including body mass estimates, surrogate variables for body size, proximal femoral articular orientation, or knee anteroposterior dimensions. The functional role of femoral anterior curvature is unknown; however, the general decrease in curvature subtense closely parallels the between-group changes in inferred levels of mobility from femoral diaphyseal robusticity and shape, suggesting that femoral curvature may reflect mobility levels and patterns among Late Pleistocene and recent humans.     

The third metacarpal styloid process in humans: origin and functions

The development, mechanics, and pathology of the third carpometacarpal joint have been investigated in order to explain the unique presence in humans of a styloid process on the third metacarpal. Structure and functions of the joint are compared in a large series of Old World anthropoid hand skeletons, cadavers, and X-rays, and shown to differ in the three groups. Developmental anomalies reveal the source of the human styloid in a group of cells which fuse with the capitate in other Old World Anthropoidea. The absence of the process in Australopithecus afarensis and its presence in Neandertals suggest that an explanation for the evolution of the process may be sought in stresses on the hand in stone tool-use. Film analysis of stone tool-use shows that hammering and digging with hand-held stones direct forces on the palmar aspect of the metacarpal head. From a biomechanical analysis of these forces it may be seen that the styloid process prevents subluxation of the base. The effectiveness of the process in this function is reflected by the rarity of injury and arthritis in the region. Individuals lacking the process tend to undergo degeneration of bone at the joint. Since repetitive impulsive forces on joints are known to cause osteoarthritis, it is suggested that there may be a link between the increasing reliance of early hominids on manipulative behavior that stressed this region of the hand and the evolution of a structural pattern that protects the joint from these stresses.     

Postcranial robusticity in Homo. I: Temporal trends and mechanical interpretation

Temporal trends in postcranial robusticity within the genus Homo are explored by comparing cross-sectional diaphyseal and articular properties of the femur, and to a more limited extent, the humerus, in samples of Recent and earlier Homo. Using both theoretical mechanical models and empirical observations within Recent humans, scaling relationships between structural properties and bone length are developed. The influence of body shape on these relationships is considered. These scaling factors are then used to standardize structural properties for comparisons with pre-Recent Homo (Homo sp. and H. erectus, archaic H. sapiens, and early modern H. sapiens). Results of the comparisons lead to the following conclusions: 1) There has been a consistent, exponentially increasing decline in diaphyseal robusticity within Homo that has continued from the early Pleistocene through living humans. Early modern H. sapiens are closer in shaft robusticity to archaic H. sapiens than they are to Recent humans. The increase in diaphyseal robusticity in earlier Homo is a result of both medullary contraction and periosteal expansion relative to Recent humans. 2) There has been no similar temporal decline in articular robusticity within Homo–relative femoral head size is similar in all groups and time periods. Thus, articular to shaft proportions are different in pre-Recent and Recent Homo. 3) These findings are most consistent with a mechanical explanation (declining mechanical loading of the postcranium), that acted primarily through developmental rather than genetic means. The environmental (behavioral) factors that brought about the decline in postcranial robusticity in Homo are ultimately linked to increases in brain size and cultural-technological advances, although changes in robusticity lag behind changes in cognitive capabilities. © 1993 Wiley-Liss, Inc.     

Femoral curvature in Neanderthals and modern humans: a 3D geometric morphometric analysis

Since their discovery, Neanderthals have been described as having a marked degree of anteroposterior curvature of the femoral shaft. Although initially believed to be pathological, subsequent discoveries of Neanderthal remains lead femoral curvature to be considered as a derived Neanderthal feature. A recent study on Neanderthals and middle and early Upper Palaeolithic modern humans found no differences in femoral curvature, but did not consider size-corrected curvature. Therefore, the objectives of this study were to use 3D morphometric landmark and semi-landmark analysis to quantify relative femoral curvature in Neanderthals, Upper Palaeolithic and recent modern humans, and to compare adult bone curvature as part of the overall femoral morphology among these populations.Comparisons among populations were made using geometric morphometrics (3D landmarks) and standard multivariate methods. Comparative material involved all available complete femora from Neanderthal and Upper Palaeolithic modern human, archaeological (Mesolithic, Neolithic, Medieval) and recent human populations representing a wide geographical and lifestyle range. There are significant differences in the anatomy of the femur between Neanderthals and modern humans. Neanderthals have more curved femora than modern humans. Early modern humans are most similar to recent modern humans in their anatomy. Femoral curvature is a good indicator of activity level and habitual loading of the lower limb, indicating higher activity levels in Neanderthals than modern humans. These differences contradict robusticity studies and the archaeological record, and would suggest that femoral morphology, and curvature in particular, in Neanderthals may not be explained by adult behavior alone and could be the result of genetic drift, natural selection or differences in behavior during ontogeny.     

Hand osteoarthritis and bone loss: Is there an inverse relationship?

An inverse relationship between osteoarthritis (OA) and bone loss has been supported in clinical research, but there has been little research on bioarchaeological skeletal remains. The current study examines 115 adults from a prehistoric hunter–gatherer population to aid in determining whether hand OA and bone loss are negatively correlated. OA lipping is scored on a four-point scale on left and right trapezia, MC1s, and MC2s and then analyzed with regard to their relationships with sex, age, right MC2 cortical index, and left and right MC1 robusticity, midshaft circumference, and midshaft diameter values. With sexes and ages combined, higher OA scores are found in individuals with greater midshaft diameters. However, lower cortical indices were found in individuals with higher right MC2 OA scores. The data presented tenuously support that bone loss is lower in individuals with more severe osteoarthritis, but age-related changes in bone deposition may make cortical index and other external shaft dimensions an unsuitable variable to examine this relationship.     

Humeral epiphyseal shape in the felidae: The influence of phylogeny,allometry, and locomotion

Bone morphology of the cats (Mammalia: Felidae) is influenced by many factors, including locomotor mode, body size, hunting methods, prey size and phylogeny. Here, we investigate the shape of the proximal and distal humeral epiphyses in extant species of the felids, based on two‐dimensional landmark configurations. Geometric morphometric techniques were used to describe shape differences in the context of phylogeny, allometry and locomotion. The influence of these factors on epiphyseal shape was assessed using Principal Component Analysis, Linear Discriminant functions and multivariate regression. Phylogenetic Generalised Least Squares was used to examine the association between size or locomotion and humeral epiphyseal shape, after taking a phylogenetic error term into account. Results show marked differences in epiphyseal shape between felid lineages, with a relatively large phylogenetic influence. Additionally, the adaptive influences of size and locomotion are demonstrated, and their influence is independent of phylogeny in most, but not all, cases. Several features of epiphyseal shape are common to the largest terrestrial felids, including a relative reduction in the surface area of the humeral head and increased robusticity of structures that provide attachment for joint‐stabilising muscles, including the medial epicondyle and the greater and lesser tubercles. This increased robusticity is a functional response to the increased loading forces placed on the joints due to large body mass. J. Morphol., 2012. © 2012 Wiley Periodicals, Inc.     

Intensity,repetitiveness, and directionality of habitual adolescent mobility patterns influence the tibial diaphysis morphology of athletes

Mobility patterns affect the loads placed on the lower limbs during locomotion and may influence variation in lower limb diaphyseal robusticity and shape. This relationship commonly forms the basis for inferring mobility patterns from hominin fossil and skeletal remains. This study assesses the correspondence between athletic histories, varying by loading intensity, repetition and directionality, measured using a recall questionnaire, and peripheral quantitative computed tomography‐derived measurements of tibial diaphysis rigidity and shape. Participants included male university varsity cross‐country runners (n = 15), field hockey players (n = 15), and controls (n = 20) [mean age: 22.1 (SD +/? 2.6) years]. Measurements of tibial rigidity (including J, %CA, I_max, I_min, and average cortical thickness) of both runners and field hockey players were greater than controls (P ≤ 0.05). Differences in tibial shape (I_max/I_min, P ≤ 0.05) between runners and hockey players reflect pronounced maximum plane (I_max) rigidity in runners, and more symmetrical hypertrophy (I_max, I_min) among hockey players. This corresponds with the generally unidirectional locomotor patterns of runners, and the multidirectional patterns of hockey players. These results support the relationship between mobility and tibial diaphysis morphology as it is generally interpreted in the anthropological literature, with greater levels of mobility associated with increased diaphyseal robusticity and shape variation. Although exercise intensity may be the primary influence on these properties, the repetitiveness of the activity also deserves consideration. In conclusion, bone morphological patterns can reflect habitual behaviors, with adaptation to locomotor activities likely contributing to variation in tibial rigidity and shape properties in archaeological and fossil samples. Am J Phys Anthropol 2009. © 2009 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.