Pronosupination is a component of the hominoid orthograde corporal plane that enables primates to execute efficient and sure locomotion in their habitat and is an essential movement for the development of manipulative capacities. We analyze human variability in the rotational efficiency of the pronator teres muscle by applying the biomechanical model created by Galt es et al. (Am J Phys Anthropol 2008; 135:293-300; Am J Phys Anthropol 2009a; 140:589-594) to skeletal remains of a human sample (N ¼ 29) and three nonhuman hominoid specimens (chimpanzee, gorilla, and orangutan) by means of 3D technology. We aim to examine whether there is a distinctive human pattern of rotational efficiency and determine which structural features of the upper-limb bones have the greatest influence on the determination of rotational efficiency. Our results show that the human pattern differs from efficiencies observed in nonhuman hominoids, which may be interpreted in the light of morphofunctional adaptations. We identify medial epicondylar form as the key structure of the upper-limb bones for the determination of the rotational efficiency of the forearm. Results indicate that the more medially projected epicondyle of nonhuman hominoids relative to humans leads to higher values of maximum rotational efficiency. Moreover, the orientation of the medial epicondyle determines the pronounced differences in the position of the maximum efficiencies in the pronosupination range between humans and the studied nonhuman hominoids. Proximodistal orientation of the medial epicondyle is suggested to be a more appropriate feature for distinguishing between humans and nonhuman hominoids than anteroposterior orientation and, therefore, for inferring behavioral aspects from skeletal remains and fossils of primate upper-limb bones.

The relationship between the mechanical loading undergone by a bone and its form has been widely assumed as a premise in studies aiming to reconstruct behavioral patterns from skeletal remains. Nevertheless, this relationship is complex due to the existence of many factors affecting bone structure and form, and further research combining structural and shape characteristics is needed. Using two-block PLS, which is a test to analyze the covariance between two sets of variables, we aim to investigate the relationship between upper-limb entheseal changes, cross-sectional properties, and contour shape of the humeral diaphysis. Our results show that individuals with strongly marked entheseal changes have increased diaphyseal rigidities. Bending rigidities are mainly related to entheseal changes of muscles that cross the shoulder. Moreover, the entheseal changes of muscles that participate in the rotation of the arm are related to mediolaterally flatter and ventrodorsally broader humeral shapes in the mid-proximal diaphysis. In turn, this diaphyseal shape is related to diaphyseal rigidity, especially to bending loadings. The shape of the diaphysis of the rest of the humerus does not covary either with rigidity or with entheseal changes. The results indicate that large muscular scars, such as those found in the mid-proximal diaphyses, seem to be related to diaphyseal shape, whereas this relationship is not seen for areas with less direct influences of powerful muscles.

Longitudinal rotation of the forearm (pronosupination) is an essential component of human manipulative tasks. The efficiency of this movement is dependent not only on the rotatory muscles but also on several morphological and structural features of the upper limb. In a recent study, we observed that the size and orientation of the humeral medial epicondyle played an important role in forearm rotatory ability. We further observed that the forearm muscular activity, specifically the motion of pronation, promotes radial curvature, which, in turn, enhances rotational efficiency. In this study, we aim to test whether the orientation of the medial epicondyle is an activity‐dependent parameter or whether it is an invariable morphological feature characteristic of the human skeleton. We analysed the upper limb entheseal changes in 30 human skeletons and assessed the role of several functional groups in the anteroposterior and proximo‐distal orientation of the medial epicondyle. Our results indicate that the orientation of the medial epicondyle is partially an activity‐dependent feature basically determined by elbow flexor‐extensors and hand and wrist flexors. The orientation of the medial epicondyle towards more posterior and proximal positions causes a gain of efficiency in the pronation range when the elbow is extended and in the supination range when the elbow is flexed. Therefore, we suggest that the medial epicondyle of the humerus is a structure involved in the manipulative capacities of the human upper limb, and its orientation presents a range of variation that may be associated with the functional enhancement of these abilities. Copyright © 2012 John Wiley & Sons, Ltd.

Biomechanical models are useful to assess the effect of muscular forces on bone structure. Using skeletal remains, we analyze pronator teres rotational efficiency and its force components throughout the entire flexion-extension and pronation-supination ranges by means of a new biomechanical model and 3D imaging techniques, and we explore the relationship between these parameters and skeletal structure. The results show that maximal efficiency is the highest in full elbow flexion and is close to forearm neutral position for each elbow angle. The vertical component of pronator teres force is the highest among all components and is greater in pronation and elbow extension. The radial component becomes negative in pronation and reaches lower values as the elbow flexes. Both components could enhance radial curvature, especially in pronation. The model also enables to calculate efficiency and force components simulating changes in osteometric parameters. An increase of radial curvature improves efficiency and displaces the position where the radial component becomes negative towards the end of pronation. A more proximal location of pronator teres radial enthesis and a larger humeral medial epicondyle increase efficiency and displace the position where this component becomes negative towards forearm neutral position, which enhances radial curvature. Efficiency is also affected by medial epicondylar orientation and carrying angle. Moreover, reaching an object and bringing it close to the face in a close-to-neutral position improve efficiency and entail an equilibrium between the forces affecting the elbow joint stability. When the upper-limb skeleton is used in positions of low efficiency, implying unbalanced force components, it undergoes plastic changes, which improve these parameters. These findings are useful for studies on ergonomics and orthopaedics, and the model could also be applied to fossil primates in order to infer their locomotor form. Moreover, activity patterns in human ancient populations could be deduced from parameters reported here.

RESUMENTrabajos recientes han descrito la existencia de diferencias sexuales y de edad en la anchura de las crestas epidérmicas en huellas dactilares humanas. El potencial forense de esta característica es muy amplio y se ha empezado a utilizar para obtener información a partir de las huellas encontradas tanto en el lugar del crimen como en objetos cerámicos antiguos. El objetivo de este estudio es determinar el sexo y la edad aproximada del autor de los dermatoglifos encontrados en un fragmento cerámico de La Canal dels Avellaners, Berga, Cataluña. Las huellas fueron comparadas con una muestra de población española contemporánea que incluía individuos de entre 6 y 58 años. Los resultados indican que el artesano fue un hombre adulto y demuestran que este tipo de investigaciones informan sobre la persona que las dejó y, por tanto, presenta un gran potencial en estudios sobre aspectos sociales de la elaboración de cerámicas en culturas antiguas. ABSTRACT