Is the lateral angle of the internal acoustic canal sexually dimorphic in non-adults? An investigation by routine cranial magnetic resonance imaging

The lateral angle of the internal acoustic canal is one of the measurements of petrous bone that has been previously studied for sex estimation, mostly in adults. We aimed at evaluating the effects of age, side, and sex on the lateral angle of the internal acoustic canal in pediatric patients.Pediatric routine cranial MRI studies were retrospectively investigated for this study. The lateral angle was measured on T2-weighted axial images when the anterior and posterior lips of the meatus and the cochlea were clearly visible on the same image. The data were evaluated for age, side and sex-related changes. Although 552 temporal bones from 273 patients were inspected, due to exclusion criteria lateral angle could be satisfactorily measured only in 101 temporal bones from 58 patients. The measurements did not differ significantly between sexes. An age-related, statistically significant decrease was observed for the entire pediatric sample studied, as well as for the males, but not for females. The measurements did not differ from side to side.The significant age-related decrease in lateral angle in male pediatric patients that was not detected in female counterparts may be the reflection of a sex-related difference in temporal bone development during childhood. Routine cranial MRI data may help investigators study age and sex-related changes in lateral angle in children.     

A biometric analysis of the pelvic acetabulum as an indicator of sex in bovids

Despite its potential importance in the reconstruction of hunting strategies and subsistence patterns, determining sex in zooarchaeological assemblages is a task that has been often neglected because the assemblages consist mainly of fragmentary bones. Only a limited amount of research has been focused on sexing individuals at archaeological sites. Although dimorphic elements in skeletal anatomy (e.g., horns) are the most widely used indicators for sexing, other skeletal parts, such as the pelvic acetabulum provide valuable information to identify sex. The present work builds upon previous research and indicates the most useful indicators in the pelvic acetabulum to distinguish sex in bovids, with the goal of providing an analytical basis to expand interpretations of carcass acquisition strategies by humans.     

Scoring system for estimating age in the foot skeleton

This study assesses chronological age of immature individuals from the degree of ossification evident in the foot skeleton. We considered all tarsal and ray bones in various combinations to determine the most sensitive indicators of chronological age. Skeletal maturity was rated according to a subjective but simple scoring system applied to radiographs of normal feet of children of known chronological age. Scales for assessing the primary center of ossification, secondary center of ossification, and state of fusion are defined. In general, as expected, females show earlier onset of skeletal maturity than males; in particular, females in our sample are skeletally mature in most elements beginning 48 months prior to the earliest incidence of skeletal maturity in males for the same bones. Females in our sample show a marked tendency toward skeletal maturity of all elements by 150 months of age, while males do not show the same tendency until approximately 200 months of age. In general within each sex, consecutive states of fusion show broad overlap in range of chronological age within each bone. Combining scores from several different bones enables a reasonable estimate of potential age in a test application of the model.     

Patterns of femoral bone remodeling dynamics in a medieval Nubian population

The relationship between age, sex and histomorphometry in femoral cortical bone was examined in a skeletal population of late Medieval antiquity (AD 1250–1450) from Kulubnarti, in Sudanese Nubia. These skeletal remains are naturally mummified and in an excellent state of preservation. The study sample consisted of femoral cross sections from 24 females and 19 males ranging in age from 20 to 50+ years. Femoral cross sections were examined using an image analysis system. Numbers of secondary osteons and osteon fragments were counted, osteon area and Haversian canal area were measured, and several variables were calculated to assess differences between sexes and among age groups in bone remodeling variables. The results indicate significant differences between the sexes in osteon number and size. Males had significantly more intact osteons than females, whereas females had significantly larger osteons than males. Haversian canal dimensions were not statistically significant between the sexes. Sex differences in activity patterns in which males were involved in more physically strenuous tasks may have contributed to differences in remodeling variables. Interpopulational comparisons suggest that mechanical strain affects the microstructural features examined in this study. In particular, small Haversian canals in some archaeological skeletal populations are associated with higher bone volume, which may result from high levels of mechanical strain. Am J Phys Anthropol 104:133–146, 1997. © 1997 Wiley-Liss, Inc.     

The bony labyrinth of Neanderthals

This paper presents a comprehensive comparative analysis of the Neanderthal bony labyrinth, a structure located inside the petrous temporal bone. Fifteen Neanderthal specimens are compared with a Holocene human sample, as well as with a small number of European Middle Pleistocene hominins, and early anatomically modern and European Upper Palaeolithic humans. Compared with Holocene humans the bony labyrinth of Neanderthals can be characterized by an anterior semicircular canal arc which is smaller in absolute and relative size, is relatively narrow, and shows more torsion. The posterior semicircular canal arc is smaller in absolute and relative size as well, it is more circular in shape, and is positioned more inferiorly relative to the lateral canal plane. The lateral semicircular canal arc is absolutely and relatively larger. Finally, the Neanderthal ampullar line is more vertically inclined relative to the planar orientation of the lateral canal. The European Upper Palaeolithic and early modern humans are most similar, although not fully identical to Holocene humans in labyrinthine morphology. The European Middle Pleistocene hominins show the typical semicircular canal morphology of Neanderthals, with the exception of the arc shape and inferiorly position of the posterior canal and the strongly inclined ampullar line. The marked difference between the labyrinths of Neanderthals and modern humans can be used to assess the phylogenetic affinities of fragmentary temporal bone fossils. However, this application is limited by a degree of overlap between the morphologies. The typical shape of the Neanderthal labyrinth appears to mirror aspects of the surrounding petrous pyramid, and both may follow from the phylogenetic impact of Neanderthal brain morphology moulding the shape of the posterior cranial fossa. The functionally important arc sizes of the Neanderthal semicircular canals may reflect a pattern of head movements different from that of modern humans, possibly related to aspects of locomotor behaviour and the kinematic properties of their head and neck.     

Study on long bones: variation in angular traits with sex, age, and laterality

The biological problems considered in this study are sexual dimorphism in angular osteometric traits, changes in these traits with aging and their bilateral asymmetry in the same individual. The sample comprises the right and left long bones of 200 skeletons (100 males and 100 females) of Sardinian adults (Frasetto collection) for whom the sex and age at death are known. As concerns the sexual dimorphism, some angular traits of upper limb (joint axis angle of the ulna in particular) and the lower limb (condylo-diaphyseal angle of the femur and retroversion angle of the tibia) are significantly different between males and females. Torsion angles of long bones (especially the femur) were found to change with age. In sides comparison revealed a clear right-left asymmetry in our sample. The asymmetry, sexual dimorphism and changes with age are discussed in relation to varying stresses of different living activities. Our data indicate that the angular traits of long bones could be very informative in biomechanical interpretations of human activities based on skeletal remains.     

Pelvic dimorphism in relation to body size and body size dimorphism in humans

Many mammalian species display sexual dimorphism in the pelvis, where females possess larger dimensions of the obstetric (pelvic) canal than males. This is contrary to the general pattern of body size dimorphism, where males are larger than females. Pelvic dimorphism is often attributed to selection relating to parturition, or as a developmental consequence of secondary sexual differentiation (different allometric growth trajectories of each sex). Among anthropoid primates, species with higher body size dimorphism have higher pelvic dimorphism (in converse directions), which is consistent with an explanation of differential growth trajectories for pelvic dimorphism. This study investigates whether the pattern holds intraspecifically in humans by asking: Do human populations with high body size dimorphism also display high pelvic dimorphism? Previous research demonstrated that in some small-bodied populations, relative pelvic canal size can be larger than in large-bodied populations, while others have suggested that larger-bodied human populations display greater body size dimorphism. Eleven human skeletal samples (total N: male = 229, female = 208) were utilized, representing a range of body sizes and geographical regions. Skeletal measurements of the pelvis and femur were collected and indices of sexual dimorphism for the pelvis and femur were calculated for each sample [ln(M/F)]. Linear regression was used to examine the relationships between indices of pelvic and femoral size dimorphism, and between pelvic dimorphism and female femoral size. Contrary to expectations, the results suggest that pelvic dimorphism in humans is generally not correlated with body size dimorphism or female body size. These results indicate that divergent patterns of dimorphism exist for the pelvis and body size in humans. Implications for the evaluation of the evolution of pelvic dimorphism and rotational childbirth in Homo are considered.     

A quantitative study of morphological and histological changes in the skeleton of Salmo salar during its anadromous migration

A quantitative study of morphological and histological changes in the skeleton (cranial bones and vertebrae) of adult Atlantic salmon Salmo salar during its anadromous migration was performed in order to specify various aspects of its skeletal biology in relationship to this migration. At the beginning of the ascent, there was no morphological difference in the cranial bones between males and females. As the spawning season approached, males showed marked secondary sexual characters particularly allometric breeding growth of some bones of the skull. The histological analysis of the vertebral bone tissue along the vertebral axis showed that bone compacity and number of trabeculae vary depending on their localization on the vertebral axis. Moreover, bone compacity decreased significantly with the sexual maturation of the fish whereas the number of trabeculae grew in both sexes. Thus, the vertebrae (like scales) represent an important source of calcium and other elements during anadromous migration in Atlantic salmon.     

Bony pelvic canal size and shape in relation to body proportionality in humans

Obstetric selection acts on the female pelvic canal to accommodate the human neonate and contributes to pelvic sexual dimorphism. There is a complex relationship between selection for obstetric sufficiency and for overall body size in humans. The relationship between selective pressures may differ among populations of different body sizes and proportions, as pelvic canal dimensions vary among populations. Size and shape of the pelvic canal in relation to body size and shape were examined using nine skeletal samples (total female n = 57; male n = 84) from diverse geographical regions. Pelvic, vertebral, and lower limb bone measurements were collected. Principal component analyses demonstrate pelvic canal size and shape differences among the samples. Male multivariate variance in pelvic shape is greater than female variance for North and South Africans. High‐latitude samples have larger and broader bodies, and pelvic canals of larger size and, among females, relatively broader medio‐lateral dimensions relative to low‐latitude samples, which tend to display relatively expanded inlet antero‐posterior (A‐P) and posterior canal dimensions. Differences in canal shape exist among samples that are not associated with latitude or body size, suggesting independence of some canal shape characteristics from body size and shape. The South Africans are distinctive with very narrow bodies and small pelvic inlets relative to an elongated lower canal in A‐P and posterior lengths. Variation in pelvic canal geometry among populations is consistent with a high degree of evolvability in the human pelvis. Am J Phys Anthropol 151:88–101, 2013. © 2013 Wiley Periodicals, Inc.     

A simple univariate technique for determining sex from fragmentary femora: its application to a Scottish short cist population

A simple univariate technique for sexing individuals represented by fragmentary skeletal remains is described. The results obtained were highly consistent (about 90%) with those obtained by conventional analysis of pelvic and cranial morphology. It is suggested that using maximum anteroposterior diameter of the femoral shaft as a sex discriminator has advantages over midshaft circumference even when intact femora are available.     

Protection of obstetric dimensions in a small-bodied human sample

In human females, the bony pelvis must find a balance between being small (narrow) for efficient bipedal locomotion, and being large to accommodate a relatively large newborn. It has been shown that within a given population, taller/larger-bodied women have larger pelvic canals. This study investigates whether in a population where small body size is the norm, pelvic geometry (size and shape), on average, shows accommodation to protect the obstetric canal. Osteometric data were collected from the pelves, femora, and clavicles (body size indicators) of adult skeletons representing a range of adult body size. Samples include Holocene Later Stone Age (LSA) foragers from southern Africa (n = 28 females, 31 males), Portuguese from the Coimbra-identified skeletal collection (CISC) (n = 40 females, 40 males) and European-Americans from the Hamann-Todd osteological collection (H-T) (n = 40 females, 40 males). Patterns of sexual dimorphism are similar in the samples. Univariate and multivariate analyses of raw and Mosimann shape-variables indicate that compared to the CISC and H-T females, the LSA females have relatively large midplane and outlet canal planes (particularly posterior and A-P lengths). The LSA males also follow this pattern, although with absolutely smaller pelves in multivariate space. The CISC females, who have equally small stature, but larger body mass, do not show the same type of pelvic canal size and shape accommodation. The results suggest that adaptive allometric modeling in at least some small-bodied populations protects the obstetric canal. These findings support the use of population-specific attributes in the clinical evaluation of obstetric risk.     

Anatomical and developmental bases for the ventral arc of the human pubis

The ventral arc of the pubis is frequently used for sexing adult human hip bones. This study addresses the issues of the anatomical and developmental bases for the ventral arc. Dissection of seven adult pelves (four females and three males) demonstrates that the sexes are identical in the muscular and ligamentous attachments to this ridge of bone. The tendons of gracilis and adductor brevis, which are fused for a variable extent, arise from the ridge of bone, and the fibers of the ventral pubic ligament attach to its medial border. Lateral placement of the ventral arc is defined in terms of the minimum distance between the ridge of bone and the inferior border of the symphyseal face of the pubis. The hypothesis that lateral placement of the ventral arc is positively correlated with pubic length was tested using two random samples of adult female hip bones (N = 50 for both whites and blacks) from the Hamann-Todd collection. The correlation between these variables is significant. The results support the argument that lateral placement of the ventral arc is related to the amount of postadolescent growth occurring at the symphyseal border of the pubis. Therefore, the ventral arc should not be considered as an independent criterion from pubic length in sexing adult hip bones.     

Sexual dimorphism in human lower limb bone structure: relationship to subsistence strategy and sexual division of labor

Cross-sectional geometric properties of the human femur and tibia are compared in males and females in a number of recent and archaeological population samples extending back to the Middle Paleolithic. There is a consistent decline in sexual dimorphism from hunting-gathering to agricultural to industrial subsistence strategy levels in properties which measure relative anteroposterior bending strength of the femur and tibia in the region about the knee. This trend parallels and is indicative of reductions in the sexual division of labor, in particular differences in the relative mobility of males and females. Sexual dimorphism in mediolateral bending strength near the hip shows no consistent temporal trend, probably reflecting relatively constant sex differences in pelvic structure related to the requirements of childbirth. Upper and Middle Paleolithic samples are indistinguishable in terms of sexual dimorphism from modern huntergatherers, suggesting a similar sexual division of labor. The results illustrate the utility of cross-sectional geometric parameters of long bone diaphyses in reconstructing behavioral differences within and between past populations. Some variations in the accuracy of sexing techniques based on diaphyseal measurements of the lower limb long bones may also be explained by these behavioral and structural factors.     

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.     

Gombe chimpanzee sex differences in the pelvis and observations of pubic and preauricular areas

The skeletons of Gombe chimpanzees provide an opportunity for analysis of bony tissue with reference to known sex and parity in combination with observations on other life history variables and behavior. Measurements of the pelvic bones show a mosaic of sex differences. Well-defined resorption areas on the dorsomedial aspect of the pubis and the preauricular area of the ilium have been associated with sex and parity in humans and other species. However, these are not present in either females or males in this chimpanzee skeletal series.     

The craniofacial skeleton in anencephalic human fetuses. I. Cranial floor

Twelve anencephalic and four normal fetuses 26 to 40 weeks gestational age were compared by anatomic, radiographic and histologic methods in order to gain information concerning morphogenesis. In the anencephalics, alterations located within the body of the sphenoid bone led to a reduced cranial floor angle and a more vertical clivus. The reduced lateral extension of the lesser and greater wings of the sphenoid constricted the anterior and middle cranial fossae respectively. The posterior cranial fossa tended to have an increased transverse dimension related to the supraoccipital and exoccipital bone orientation. The increased anterior and inferior position of the lateral end of the petrous temporal ridge was positively correlated with the degree of dorsal schisis in the anencephalics. Alterations in the size, form, or duration of the neural functional matrix are suggested as the cause of changes in the cranial floor.     

Morphological variation in adult chimpanzees (Pan troglodytes verus) of the Taï National Park, Côte d'Ivoire

Twenty five adult chimpanzee skeletons (Pan troglodytes verus) of known age and sex (15 females, 10 males) from a long‐term study site in Taï National Park, Cote d'Ivoire present new data on variation. These skeletons provide a rare opportunity to measure the cranium and postcranium from the same individuals. We compare measurements and indices of the Taï sample with those of relatively complete Pan troglodytes schweinfurthii skeletons from Gombe National Park, Tanzania. Measurements of Pan paniscus are included as an outside comparison. The Taï and Gombe samples are analyzed by sex; combined sex samples are compared between the two groups, and the two sexes to each other. Taï females and males do not differ in most long bone lengths or in pelvic dimensions, but do differ significantly in cranial capacity, facial measurements, clavicle length, scapular breadth, and femur length. Gombe females and males differ significantly in some facial measurements and in scapular breadth. In combined sex samples, Taï individuals have lower cranial capacity, longer palate and mandible, and greater dimensions in the trunk and limb lengths. Taï females account for most of the variation; males differ from each other only in greater length of humerus and femur. The Taï skeletons provide new data for assessing individual variation and sexual dimorphism within and between populations and species. The combination of cranial and postcranial data provides a clearer picture of chimpanzee intraspecific and interspecific variation than can be gained from either data set alone. Am J Phys Anthropol, 2008. © 2007 Wiley‐Liss, Inc.     

Age and Sex Determination in the Water Vole (<Emphasis Type="Italic">Arvicola amphibius</Emphasis>, Rodentia,Arvicolinae) Based on Measurements of the Pelvic Limb Bones

A method was developed for determining the age and sex of the water vole (Arvicola amphibius L.) based on the measurements of the pelvic limb bones. The material was obtained from captive-bred animals of a known age. By using discriminant analysis, classification functions were found for dividing the animals of the sample analyzed (n = 56) by sex and age with an accuracy equal to one year. Testing the control group (n = 34) showed that the age of 90.0% of males and of 92.9% of females was determined correctly. The correctness of the classification by sex is 100%.     

Development of the supraorbital and mandibular lateral line canals in the cichlid,Archocentrus nigrofasciatus

The development of two of the cranial lateral line canals is described in the cichlid, Archocentrus nigrofasciatus. Four stages of canal morphogenesis are defined based on histological analysis of the supraorbital and mandibular canals. "Canal enclosure" and "canal ossification" are defined as two discrete stages in lateral line canal development, which differ in duration, an observation that has interesting implications for the ontogeny of lateral line function. Canal diameter in the vicinity of individual neuromasts begins to increase before ossification of the canal roof in each canal segment; this increase in canal diameter is accompanied by an increase in canal neuromast size. The mandibular canal generally develops later than the supraorbital canal in this species, but in both of these canals development of the different canal segments contained within a single dermal bone is asynchronous. These observations suggest that a dynamic process requiring integration and interaction among different tissues, in both space and time, underlies the development of the cranial lateral line canal system. The supraorbital and mandibular canals appear to demonstrate a "one-component" pattern of development in Archocentrus nigrofasciatus, where the walls of each canal segment grow up from the underlying dermal bone and then fuse to form the bony canal roof. This is contrary to numerous published reports that describe a "two-component" pattern of development in teleosts where the bony canal ossifies separately and then fuses with an underlying dermal bone. A survey of the literature in which lateral line canal development is described using histological analysis suggests that the occurrence of two different patterns of canal morphogenesis ("one-component" and "two-component") may be due to phylogenetic variation in the pattern of the development of the lateral line canals.     

Growth of skeletal components in the young squirrel monkey (Saimiri sciureus boliviensis): a longitudinal experiment

A functional skeletal criterion, as an extension of the van der Klaauw's cranial theory, was adopted in the present study. The null hypothesis tested was: "The major skeletal components of the platyrrhine body grow linearly, regardless of their functional dependence to different demands." The acceptance of the hypothesis will imply that all Saimiri skeletal growth may be satisfactorily explained by independent variables in a single equation. The rejection will suggest that such skeletal growth patterns have to be explained by variables in several different equations, and perhaps these equations may vary with the effect of sex and undernutrition. Control and undernourished squirrel monkeys were radiographed monthly for 2 years; they were also measured; and their volumetric and morphometric neurocranial, facial, and pelvic indices were calculated. The curves that best described each of the 24-point sequences were obtained. Three main growth patterns were observed: 1) Simple linear (femur length for all groups, and pelvic index for control and undernourished females), for which the simple regression equation explained more than 95% of the variation; 2) Complex linear (pelvic index for control and undernourished males, and neurocranial and facial indices for all of the groups), for which more than 95% of the variation was explained by one of the four four-function type equations; and 3) Noncorrelated with age (neurofacial index for undernourished males, and pelviofemoral index for control females and undernourished males and females), which showed nonsignificant correlations with respect to age. The food intake and the oscillations of the environmental temperature might help to explain the undulating growth trajectory observed in the complex linear components.