Technical note: Development of regression equations to reassociate upper limb bones from commingled contexts.

The major upper limb skeletal elements (scapulae, humeri, ulnae and radii) are frequently utilized for sex determination and stature estimation. Consequently, in forensic cases that involve commingled remains, it is crucial to reassociate the aforementioned bones and attribute them to the right individual. The aim of the present study is to develop simple and multiple regression equations for sorting commingled human skeletal elements of the upper limb. In that context, ten common anthropological linear measurements of the articular surfaces of scapulae, humeri, ulnae, and radii were performed on 222 adult skeletons from the Athens Collection. The functions developed for sorting adjoining bones presented a strong positive linear relationship (r=0.69-0.93, p<0.05). The values of the determination coefficient statistics (r2=0.47-0.86) were found to be high and those of the standard errors of the estimate were found to be low (SEE=0.88-1.61). Blind tests indicated that when metric and morphoscopic sorting techniques are combined, a reliable sorting of the skeletal elements of the upper limbs is possible.

Statistical shape analysis of hand and wrist in paediatric population on radiographs

Background/aim: The goal of this study was to compare differences in hand and wrist shapes and to evaluate these according to growth and allometry in children on radiographs related to bone age. Materials and methods: The study included 263 males and 189 females. A total of 452 left hand and wrist radiographs were retrospectively collected. Standard anatomical landmarks marked on radiographs. Results: There were seen to be significant differences in comparisons of hand and wrist shapes according to sex (P = 0.009). The most suitable model in the growth models was seen as the Gompertz growth model for both females and males (model P < 0.001). For the relationship between shape and size to evaluate allometry, significant models were obtained in females (model P = 0.017, MSE = 0.0002) and in males (model P < 0.001, MSE = 0.0002). In our study, the difference between the sexes was found mostly in the radiocarpal region. It was observed that the deformation of the carpal bones started in the distal row carpal bones. Conclusion: Significant differences were found in hand and wrist shapes according to sex. Models for growth and allometry of hand and wrist shapes were found to be significant in children.

Covariation between forelimb muscle anatomy and bone shape in an Australian scratch-digging marsupial: Comparison of morphometric methods.

The close association between muscle and bone is broadly intuitive; however, details of the covariation between the two has not been comprehensively studied. Without quantitative understanding of how muscle anatomy influences bone shape, it is difficult to draw conclusions of the significance of many morphological traits of the skeleton. In this study, we investigated these relationships in the Quenda (Isoodon fusciventer), a scratch-digging marsupial. We quantified the relationships between forelimb muscle anatomy and bone shape for animals representing a range of body masses (124-1,952 g) using two-block partial least square analyses. Muscle anatomy was quantified as muscle mass and physiological cross-sectional area (PCSA), and we used two morphometric methods to characterize bone shape: seven indices of linear bone proportions, and landmarks analysis. Bone shape was significantly correlated with body mass, reflecting allometric bone growth. Of the seven bone indices, only shoulder moment index (SMI) and ulna robustness index (URI) showed a significant covariation with muscle anatomy. Stronger relationships between muscle anatomy and forelimb bone shape were found using the landmark coordinates: muscle mass and PCSA were correlated with the geometric shape of the scapula, humerus, and third metacarpal, but to a lesser extent with shape of the ulna. Overall, our data show that landmark coordinates are more sensitive than bone indices to capturing shape changes evident throughout ontogeny, and is therefore a more appropriate method to investigate covariation with forelimb muscle anatomy. Single-species studies investigating ontogeny require refined methods to accurately develop understanding of the important relationships between muscle force generation and bone shape remodeling. Landmark analyses provide such a method.

Development of discriminant functions to estimate sex in upper limb bones for mixed ancestry South Africans.

South Africa has one of the highest murder rates in the world, which is associated with an increasing number of unidentified individuals. Forensic anthropologists can assist in these cases to reduce the number of potential victims the remains may belong to. Sex estimation potentially decreases the number of possible victims by half. The mixed ancestry population in South Africa is the second largest group of people; however, there remains a paucity of data and population-specific methods for sex estimation in this group. The aim of this study was to assess the potential for metrices obtained around the nutrient foramen and the maximum length of upper limb long bones to estimate sex in mixed ancestry South Africans using discriminant function analysis. A total of 328 humeri, radii and ulnae from individuals of mixed ancestry were analysed. Sex was correctly classified with an average classification accuracy of 84.3% in the humeri, 88.3% for radii and 83.5% for the ulnae. Total length was the single best predictor of sex; the combination of total length with dimensions related to the nutrient foramen produced high classification accuracies in the current study. Overall, sexual dimorphism was observed in mixed ancestry South Africans upper limb long bones. The findings of this study further emphasise the need for population-specific standards of sexing in an attempt to improve current methods of forensic identification of descendants.

Anatomia óssea e muscular do antebraço e mão de Chrysocyon brachyurus (carnivora, canidae) / Bone and muscular anatomy of the antibone and hand of Chrysocyon brachyurus (carnivora, canidae)

O lobo-guará Chrysocyon brachyurus Illiger, 1815, é o maior canídeo da América do Sul, pesa cerca de 25 kg quando adulto e está ameaçado de extinção. Descrições anatômicas contribuem para a complementação das informações sobre espécies silvestres e para implicações conservacionistas, clínicas e cirúrgicas. Objetivou-se descrever os ossos e os músculos do antebraço e mão do lobo-guará. A preparação das peças foi feita a partir dos métodos usuais de dissecação, em animais preservados em solução de formol a 10%. Os espécimes pertencem ao acervo didático do Laboratório de Ensino e Pesquisa em Animais Silvestres da UFU e são provenientes de indivíduos atropelados. Os ossos descritos foram: rádio, ulna, ossos cárpico acessório, cárpico ulnar e cárpico intermédio; ossos cárpicos I, II, III e IV; ossos metacárpicos I, II, III, IV, V; falanges proximais, falanges médias e falanges distais do primeiro ao quinto dedo. Os músculos observados foram: extensor radial do carpo; pronador redondo; braquiorradial; extensor comum dos dedos; extensor ulnar do carpo; extensor lateral dos dedos;supinador; abdutor longo do dedo I; flexor radial do carpo; flexor profundo dos dedos; flexor superficial dos dedos; flexor ulnar do carpo; pronador quadrado; interflexor; lumbricais; abdutor curto dos dedos I e II e flexor curto do dedo I.

The maned wolf Chrysocyon brachyurus (Illiger, 1815) is the largest canid in South America, weighs about 25 kg as an adult and is threatened of extinction. Anatomical descriptions contribute to the complementation of information on wild species and for conservation, clinical and surgical implications. The purpose of this study was to describe the bones and muscles of the forearm and hand of the maned wolf. The methodology was through the usual dissecting methods in animals preserved in 10% formalin solution. The animals belong to the didactic collection of the Laboratory of Teaching and Research in Wild Animals of the UFU and come from run over. The bones evaluated were: radius, ulna, carpal accessory, carpi ulnar and carpi intermedium; carpal bones I, II, III and IV; metacarpal bones I, II, III, IV, V; proximal phalanges, middle phalanges and distal phalanges from first to fifth finger. The muscles observed were: radial extensor carpal; pronator round; brachioradial; common extensor of fingers; ulnar carpal extensor; lateral extensor of the fingers; supinator; abductor long finger I; flexor carpi radialis; flexor deep fingers; superficial flexor of the fingers; ulnar flexor of the carpus; square pronator; interflexor; lumbrils; short abductor of fingers I and II and short flexor of finger I.

The long limb bones of the StW 573 Australopithecus skeleton from Sterkfontein Member 2: Descriptions and proportions.

Due to its completeness, the A.L. 288-1 ('Lucy') skeleton has long served as the archetypal bipedal Australopithecus. However, there remains considerable debate about its limb proportions. There are three competing, but not necessarily mutually exclusive, explanations for the high humerofemoral index of A.L. 288-1: (1) a retention of proportions from an Ardipithecus-like chimp/human last common ancestor (CLCA); (2) indication of some degree of climbing ability; (3) allometry. Recent discoveries of other partial skeletons of Australopithecus, such as those of Australopithecus sediba (MH1 and MH2) and Australopithecus afarensis (KSD-VP-1/1 and DIK-1/1), have provided new opportunities to test hypotheses of early hominin body size and limb proportions. Yet, no early hominin is as complete (>90%), as is the ∼3.67 Ma 'Little Foot' (StW 573) skeleton from Sterkfontein Member 2. Here, we provide the first descriptions of its upper and lower long limb bones, as well as a comparative context of its limb proportions. We found that StW 573 possesses absolutely longer limb lengths than A.L. 288-1, but both skeletons show similar limb proportions. This finding seems to argue against a purely allometric explanation for A.L. 288-1 limb proportions. In fact, our multivariate allometric analysis suggests that limb lengths of Australopithecus, as represented by StW 573 and A.L. 288-1, exhibit a significantly different (p < 0.001) allometric pattern than that which typifies modern humans and African apes. Like some previous analyses, our results also suggest that hominin limb evolution occurred in two stages with: first, a modest increase in lower limb length and a concurrent shortening of the antebrachium between Ardipithecus and Australopithecus, followed by a considerable lengthening of the lower limb along with a decrease of both upper limb elements occurring between Australopithecus and Homo sapiens.

Variations in epiphyseal fusion and persistence of the epiphyseal line in the appendicular skeleton of two identified modern (19th-20th c.) adult Portuguese and Italian samples.

OBJECTIVES: The aim of this work is to study age, sex, and population variations in epiphyseal fusion and persistence of the epiphyseal line in the appendicular skeleton of two identified modern (19th-20th c.) adult skeletal samples, using a specifically designed macroscopic scoring method. The use of epiphyseal closure and persistence of the epiphyseal line as an adult-age marker is also discussed. MATERIALS AND METHODS: This study examined 981 adult skeletons of both sexes from two identified modern (20th c.) skeletal samples from the Sassari Collection (Museum of Anthropology, University of Bologna, Italy) and the Colecção de Esqueletos Identificados (Museum of Anthropology, University of Coimbra, Portugal). Our scoring method considers a five-degree scale, from nonfusion (Degree 0) to complete fusion (Degree 4). In addition, the persistence of the epiphyseal line, a feature that is not commonly collected during routine anthropological analyses, is taken into account here as Degree 3. RESULTS: Intra- and interobserver errors of 1.2% and 5.2%, respectively, were found, suggesting a good reproducibility of this scoring method. Some sites show variable degrees of epiphyseal fusion still in adult skeletons (e.g., secondary center of ossification of the clavicle, iliac crest, ischial tuberosity, distal epiphysis of the radius and ulna). CONCLUSIONS: Population differences have been observed, showing a delay in the complete epiphyseal closure for the Sassari sample compared to the Coimbra sample. Degree 3 seems to be a good adult-age indicator for individuals less than 35-year-old.

Hominin vertebrae and upper limb bone fossils from Sterkfontein Caves, South Africa (1998-2003 excavations).

OBJECTIVES: We provide descriptions and functional interpretations of 11 >2.0 Ma hominin vertebral and upper limb fossils from Sterkfontein. MATERIALS AND METHODS: We employed taphonomic methods to describe postmortem damage observed on the fossils. We used osteometric tools and measurements to generate quantitative descriptions, which were added to qualitative descriptions of the fossils. These observations were then interpreted using published data on the same skeletal elements from extant and extinct hominoid taxa. RESULTS: Six of the fossils carry carnivore tooth marks. Two vertebrae show morphologies that are consistent with fully developed lordosis of the lumbar spine, but which are not completely consistent with bipedal loading of the same intensity and/or frequency as reflected in the lumbars of modern humans. A clavicle shows a combination of humanlike and apelike features, the latter of which would have endowed its hominin with good climbing abilities. When combined, analyses of fragmentary radius and ulna fossils yield more ambiguous results. DISCUSSION: The new fossil collection presents a mix of bipedal and climbing features. It is unclear whether this mix indicates that all Sterkfontein hominins of >2.0 Ma were terrestrial bipeds who retained adaptations for climbing or whether the collection samples two differently adapted, coeval hominins, Australopithecus africanus and Australopithecus prometheus, both of which are represented at Sterkfontein by skull remains. Regardless, the significant frequency of tooth-marked fossils in the sample might indicate that predation was a selection pressure that maintained climbing adaptations in at least some Sterkfontein hominins of this period.

Do forelimb shape and peak forces co-vary in strepsirrhines?

OBJECTIVES: In this study, we explore whether ground reaction forces recorded during horizontal walking co-vary with the shape of the long bones of the forelimb in strepsirrhines. To do so, we quantify (1) the shape of the shaft and articular surfaces of each long bone of the forelimb, (2) the peak vertical, mediolateral, and horizontal ground reaction forces applied by the forelimb during arboreal locomotion, and (3) the relationship between the shape of the forelimb and peak forces. MATERIALS AND METHODS: Geometric morphometric approaches were used to quantify the shape of the bones. Kinetic data were collected during horizontal arboreal walking in eight species of strepsirrhines that show variation in habitual substrate use and morphology of the forelimb. These data were then used to explore the links between locomotor behavior, morphology, and mechanics using co-variation analyses in a phylogenetic framework. RESULTS: Our results show significant differences between slow quadrupedal climbers (lorises), vertical clinger and leapers (sifaka), and active arboreal quadrupeds (ring-tailed lemur, ruffed lemur) in both ground reaction forces and the shape of the long bones of the forelimb, with the propulsive and medially directed peak forces having the highest impact on the shape of the humerus. Co-variation between long bone shape and ground reaction forces was detected in both the humerus and ulna even when accounting for differences in body mass. DISCUSSION: These results demonstrate the importance of considering limb-loading beyond just peak vertical force, or substrate reaction force. A re-evaluation of osseous morphology and functional interpretations is necessary in light of these findings.

Comparison of musculoskeletal networks of the primate forelimb.

Anatomical network analysis is a framework for quantitatively characterizing the topological organization of anatomical structures, thus providing a way to compare structural integration and modularity among species. Here we apply this approach to study the macroevolution of the forelimb in primates, a structure whose proportions and functions vary widely within this group. We analyzed musculoskeletal network models in 22 genera, including members of all major extant primate groups and three outgroup taxa, after an extensive literature survey and dissections. The modules of the proximal limb are largely similar among taxa, but those of the distal limb show substantial variation. Some network parameters are similar within phylogenetic groups (e.g., non-primates, strepsirrhines, New World monkeys, and hominoids). Reorganization of the modules in the hominoid hand compared to other primates may relate to functional changes such as coordination of individual digit movements, increased pronation/supination, and knuckle-walking. Surprisingly, humans are one of the few taxa we studied in which the thumb musculoskeletal structures do not form an independent anatomical module. This difference may be caused by the loss in humans of some intrinsic muscles associated with the digits or the acquisition of additional muscles that integrate the thumb more closely with surrounding structures.

Forearm pronation efficiency in A.L. 288-1 (Australopithecus afarensis) and MH2 (Australopithecus sediba): Insights into their locomotor and manipulative habits.

OBJECTIVES: The locomotor and manipulative abilities of australopithecines are highly debated in the paleoanthropological context. Australopithecus afarensis and Australopithecus sediba likely engaged in arboreal locomotion and, especially the latter, in certain activities implying manipulation. Nevertheless, their degree of arboreality and the relevance of their manipulative skills remain unclear. Here we calculate the pronation efficiency of the forearm (Erot ) in these taxa to explore their arboreal and manipulative capabilities using a biomechanical approach. MATERIALS AND METHODS: Three-dimensional humeral images and upper limb measurements of A.L. 288-1 (Au. afarensis) and MH2 (Au. sediba) were used to calculate Erot using a previously described biomechanical model. RESULTS: Maximal Erot in elbow flexion occurs in a rather supinated position of the forearm in Au. afarensis, similarly to Pan troglodytes. In elbow extension, maximal Erot in this fossil taxon occurs in the same forearm position as in Pongo spp. In Au. sediba the forearm positions where Erot is maximal are largely coincident with those for Hylobatidae. CONCLUSIONS: The pattern in Au. afarensis suggests relevant arboreal capabilities, which would include vertical climbing, although it is suggestive of poorer manipulative skills than in modern humans. The similarity between Au. sediba and Hylobatidae is difficult to interpret, but the differences between Au. sediba and Au. afarensis suggest that the capacity to rotate the forearm followed different evolutionary processes in these australopithecine species. Although functional inferences from the upper limb are complex, the observed differences between both taxa point to the existence of two distinct anatomical models.

Sex estimation using dimensions around the nutrient foramen of the long bones of the arm and forearm in South Africans.

South Africa has had an increase in rates of crime, interpersonal violence and homicide since the introduction of democracy in 1994. Forensic osteological standards was lacking for South Africans of different population groups necessitating the generation of new standards for forensic identification of individuals from skeletal remains. For these reasons, there is a concerted demand for methods of identifying skeletal remains with sex being amongst the most important of the biological characteristics required. The nutrient foramen has been used to estimate sex in lower limb long bones with much accuracy but this has not been demonstrated in the upper limb long bones. The aim of this study was to develop osteometric standards for sex estimation from measurements around the nutrient foramen of the arm and forearm bones of South Africans of different population affinities. A total of 660 bones consisting of humeri, radii and ulnae of black South Africans and white South Africans were assessed for sex estimation using dimensions related to the nutrient foramen. Sex was correctly classified with a range of 84-85% for the humerus and 83-88% for the arm bones. The study showed that length measurements were more sexually dimorphic than width dimensions in South Africans, as length was consistently selected as the best predictor of sex in all bones. However, the average accuracy increased when length was used in combination with measurements related to the nutrient foramen. In conclusion, the dimensions of upper limb long bones that are directly related to the nutrient foramen are sexually dimorphic and are useful in the estimation of sex in South Africans, with the highest accuracy shown in the white South African population group.

Pronation and supination of the hand: Anatomy and biomechanics.

Proper functioning of the hand relies on its capacity to rotate and point the palm upward (i.e. supination) or downward (i.e. pronation) when standing up with the elbow in 90° flexion. Hand rotation is possible because of forearm rotation and also rotation of the whole upper limb at the shoulder. Two distinct mechanisms contribute to hand rotation: one in which the ulna is immobile and another in which the ulna is mobile. In this review, we first summarize how evolution of the human species has led to the progressive development of specific forearm anatomy that allows for pronation and supination. Then we analyze how the three joints of the forearm (i.e. proximal, middle and distal radioulnar joints), in association with the characteristic shape of both forearm bones, allow the forearm to rotate around a single axis. Lastly, we describe the neuromuscular anatomy that controls these complex rotational movements. The anatomical and biomechanical points developed in this paper are analyzed while considering clinical applications.

The upper limb of Homo naledi.

The evolutionary transition from an ape-like to human-like upper extremity occurred in the context of a behavioral shift from an upper limb predominantly involved in locomotion to one adapted for manipulation. Selection for overarm throwing and endurance running is thought to have further shaped modern human shoulder girdle morphology and its position about the thorax. Homo naledi (Dinaledi Chamber, Rising Star Cave, Cradle of Humankind, South Africa) combines an australopith-like cranial capacity with dental characteristics akin to early Homo. Although the hand, foot, and lower limb display many derived morphologies, the upper limb retains many primitive traits. Here, we describe the H. naledi upper extremity (excluding the hand) in detail and in a comparative context to evaluate the diversity of clavicular, scapular, humeral, radial, and ulnar morphology among early hominins and later Homo. Homo naledi had a scapula with a markedly cranially-oriented glenoid, a humerus with extremely low torsion, and an australopith-like clavicle. These traits indicate that the H. naledi scapula was situated superiorly and laterally on the thorax. This shoulder girdle configuration is more similar to that of Australopithecus and distinct from that of modern humans, whose scapulae are positioned low and dorsally about the thorax. Although early Homo erectus maintains many primitive clavicular and humeral features, its derived scapular morphology suggests a loss of climbing adaptations. In contrast, the H. naledi upper limb is markedly primitive, retaining morphology conducive to climbing while lacking many of the derived features related to effective throwing or running purported to characterize other members of early Homo.

Secular Changes in the Postcranial Skeleton of American Whites.

Secular change in height has been extensively investigated, but size and shape of the postcranial skeleton much less so. The availability of large, documented collections of nineteenth- and twentieth-century skeletons makes it possible to examine changes in skeletal structure over the past 150 years. We examined secular changes in long bone lengths and proportions, their allometric relationship to stature, and crosssectional properties of long bone shafts. Bone measurements and stature were organized into 10-year birth cohorts, ranging from 1840 to 1989. Variation among cohorts was tested by one-way ANOVA, and secular trend was examined visually by plotting mean measurements by birth decade. Allometry was examined by regressing log bone lengths onto log stature, using least squares regression. Allometry was also examined using the geometric mean of log bone lengths as the size variable. All bone lengths and stature showed positive secular change. Stature and the distal long bones showed the most pronounced changes. Proportions also changed, as revealed by the brachial and crural indices. Both indices increased, but the brachial index change was the most pronounced. Allometric relationships suggest that brachial index changes result from positive allometry of the radius and negative allometry of the humerus. Similar but less marked allometric relationships were found in the tibia and femur. Long bone shaft properties changed in the following ways: femur midshafts and tibia shafts at the nutrient foramen became more mediolaterally narrowed, and the femur became more mediolaterally thickened at the subtrochanteric level, approaching platymeria. All major long bones became more gracile. These remarkable changes in the postcranial skeleton are a response to the unparalleled changes in the environment in which modern Americans now live. Changes in growth resulting from plentiful and secure nutrition, reduced disease load, and marked reduction in bone loading from reduced activity levels are mainly responsible.

An alternative approach for estimating stature from long bones that is not population- or group-specific.

An accurate and precise estimate of stature can be very useful in the analysis of human remains in forensic cases. A problem with many stature estimation methods is that an unknown individual must first be assigned to a specific group before a method can be applied. Group membership has been defined by sex, age, year of birth, race, ancestry, continental origin, nationality or a combination of these criteria. Univariate and multivariate sex-specific and generic equations are presented here that do not require an unknown individual to be assigned to a group before stature is estimated. The equations were developed using linear regression with a sample (n=244) from the Terry Collection and tested using independent samples from the Forensic Anthropology Databank (n=136) and the Lisbon Collection (n=85). Tests with these independent samples show that (1) the femur provides the best univariate results; (2) the best multivariate equation includes the humerus, femur and tibia lengths; (3) a generic equation that does not require an unknown to first be assigned to a given category provides the best results most often; (4) a population-specific equation does not provide better results for estimating stature; (5) sex-specific equations can provide slightly better results in some cases; however, estimating the wrong sex can have a negative impact on precision and accuracy. With these equations, stature can be estimated independently of age at death, sex or group membership.

Developmental patterns of bilateral asymmetry in ancestral puebloans.

OBJECTIVES: Producing and maintaining a bilaterally symmetric phenotype throughout the lifespan is energetically demanding. Over the course of an individual's life, various intrinsic and external stressors impact the growth trajectory. These perturbations can compromise the allocation of energetic resources to processes that maintain developmental precision, potentially resulting in bilateral asymmetry (BA). Because different stressors are present during the lifespan, BA is a valuable tool for examining the unique factors impacting symmetrical growth and development. This study examines BA in paired long bones across a developmental skeletal series. METHODS: The humeri, radii, femora, and tibiae of 198 individuals from Ancestral Puebloan New Mexico (919-1670 CE) are analyzed to explore BA across development. Individuals are separated into five age categories, and by sex when possible, to explore patterns of BA. RESULTS: Significant BA is found in the bones of the upper limb when the interaction between bone and age is examined. Results suggest that BA in the humerus and radius becomes more right-biased with age. These directional trends are not observed in the lower limbs. Division into age categories illuminates patterns of asymmetry associated with age-related activities and physiological maturity, indicating that BA is differentially affected by varying environmental stressors across development. CONCLUSIONS: Our findings support the hypothesis that BA in long bones is influenced by environmental stressors that impact an individual's ability to produce symmetric morphological traits over the lifespan. Right-biased BA in the upper limb bones indicates that this variation from a symmetric ideal is strongly influenced by handedness resulting from habitual manual activities. Am. J. Hum. Biol. 28:421-430, 2016. © 2015 Wiley Periodicals, Inc.

Activity-related sexual dimorphism in Alaskan foragers from Point Hope: Evidences from the upper limb.

Ipiutak (100BCE-500CE) and Tigara (1200 - 1700CE) are two populations from Point Hope, Alaska. As commonly observed in forager communities, it may be expected males and females to have been involved in markedly different daily activities. Nevertheless, activity-related sexual dimorphism in these populations has been scarcely studied. Using humeral diaphyseal cross-sectional properties and forearm rotational efficiency, which are activity-dependent characteristics, we aim to assess differences between sexes and discuss what activities could have triggered them. Our results suggest that in Ipiutak males and females did not differ meaningfully in their cross-sectional properties. Conversely, in Tigara males had a greater rigidity of the entire humeral diaphysis than females, which suggests the existence of greater relative activity levels and more physically demanding tasks, possibly related to hunting activities. Concerning the differences between sexes in the forearm rotational efficiency, in Tigara females rotational efficiency in elbow flexion is maximal in a more supinated position than in males, which leads to an improvement of efficiency in those stages related to manipulation, and so improves the manipulative capacities of the upper limb. These differences in efficiency are caused by a more proximally oriented humeral medial epicondyle in females, which is thus confirmed to be a good feature to assess differences in labor. Therefore females in Tigara probably performed in a daily basis household activities, such as hide processing and other manipulative labors. In Ipiutak, the analysis of forearm rotational efficiency did not reveal differences between sexes. Overall, the results suggest that division of labor in Ipiutak was not as marked as in Tigara, where upper limb skeletal structure supports the idea that both sexes were involved in different daily activities. Nevertheless, the generalized lack of results in Ipiutak could be due to the small sample size, and thus interpretations should be considered with caution.

Sexual dimorphism in directional asymmetry of the upper limb bones among Khoe-San skeletons.

Right side-biased directional asymmetries in upper limb bones are described for non-human primates, modern humans and also for historical populations. According to numerous studies the degree of bilateral asymmetries varies by sex, possibly due to sex-typical labor division. The present study focused on sexual dimorphism in bilateral asymmetries of the upper limb bones among a historical Khoe-San skeletal sample, the Pöch Collection housed at the Department of Anthropology at the University of Vienna. Forty metric dimensions of humeri, ulnae, radii and clavicles of 83 adult Khoe-San individuals were measured. Directional and absolute asymmetries of each measurement were calculated. With the exception of maximal clavicle length, a significant right-biased asymmetry could be documented for both sexes. Regarding sex differences, it could be shown that a markedly greater percentage of right side dominant asymmetry of humerus length and upper limb length was found among females, while male skeletons exhibited a significantly greater percentage of absolute asymmetry in breadth and circumference dimensions, indicating a greater asymmetry in traits of robustness. These sex differences can be interpreted as a result of sex-typical labor division in this traditional historical population.

Cross-sectional structural variation relative to midshaft along hominine diaphyses. I. The forelimb.

OBJECTIVES: Analyses of hominine forelimb diaphyseal structure typically employ sections located at midshaft. This study addresses three questions. First, how accurately must midshaft be defined to yield comparable data? Second, does variation in midshaft location due to alternative definitions fall within error ranges such that data gathered using different length measurements are comparable? Third, do error ranges and length metric effects differ between elements or taxa such that certain bones or species are more prone to issues of comparability? MATERIALS AND METHODS: Humeri, radii, and ulnae of Homo, Pan, and Gorilla were CT-scanned at full length and error ranges for three structural parameters (CSA, J, Imax /Imin ) were calculated around midshafts. RESULTS: Distances proximally and distally from midshaft where structural values become significantly different from midshaft values vary between elements, taxa, and structural parameters. Error ranges are largest for the humerus and smallest for the ulna. Among taxa, error ranges for gorillas are largest and those for humans are smallest. Among structural parameters, error ranges depend on element and taxon such that no parameter consistently exhibits larger or smaller error ranges across all bones or species. Variation in midshaft locations originating from different length definitions is small and falls within error ranges defined by maximum length across all elements and taxa. DISCUSSION: Including fragmentary specimens for which midshaft location is uncertain in comparisons of forelimb diaphyseal structure requires evaluation on a case-by-case basis, with consideration to element, taxon, and structural traits of interest. However, midshaft data for all three structural parameters considered here that are recorded using different length measurements can be reasonably compared.