#Human vs chimpanzee hand series#

But as the human arm elevates, the width of the subacromial space decreases further, reducing the space the supraspinatus tendon occupies. This space is narrow, as a result of a laterally projecting acromion that often slopes inferiorly ( Voisin et al., 2014). The subacromial space is the area between the humeral head and the acromion of the scapula, through which the supraspinatus tendon passes ( Bey et al., 2007). The modern human shoulder is primarily adapted for non-locomotor, below shoulder-height behaviors, despite a possible arboreal ancestry ( Arias-Martorell, 2019 Larson, 2007 Lewis et al., 2001 Oxnard, 1969 Thorpe et al., 2007 Veeger and van der Helm, 2007 Young et al., 2015). Computational biomechanical models offer an alternative to morphological and experimental approaches by incorporating properties of musculoskeletal function and motor control dynamics using information obtained from musculoskeletal structure to simulate functionality ( Hutchinson, 2012). Comparative experimental work, while highly valuable, has been limited by subject availability and compliance, and procedural modifications for non-human subjects may reduce data precision and generalizability ( Stevens and Carlson, 2008). Although bone shape has been linked to function ( Oxnard, 1969), the individual plasticity of skeletal features and the effect of external stimuli in altering morphological features reduce the correlation ( Collard and Wood, 2000 Young, 2005). However, both methods include problematic aspects. Experimental research quantifies differences between species in locomotor behavior, and provides clues as to probable adaptions following divergence from a common ancestor.

Experimental studies complement morphometric analyses, typically by quantifying and comparing locomotor and evolutionarily relevant tasks between different primate species ( Bertram and Chang, 2001 Demes and Carlson, 2009 Larson, 1988 Larson and Stern, 2013 Stern and Larson, 2001).

#Human vs chimpanzee hand series#

This often involves comparisons of single skeletal features, or a series of skeletal features from fossils for association of form with function with extant hominids such as humans and the great apes ( Young, 2008). For evolutionary science, comparative morphometric assessment persistently emerges as a primary historical method to quantify the physical abilities and locomotion of human relatives and ancestors. Studies of evolution and biomechanics typically fall into three categories – comparative, experimental and modeling ( Pontzer et al., 2009). These results agree with previous work on inter-species differences that inform basic human rotator cuff function and pathology. Compared with chimpanzees, the human model predicted a 2 mm narrower subacromial space, deltoid muscle forces that were often double those of chimpanzees and a strong reliance on infraspinatus and teres minor (60–100% maximal force) over other rotator cuff muscles. Using static postural data of a horizontal bimanual suspension task, predicted muscle forces and subacromial space were compared between chimpanzees and humans. Together, these modules use postural kinematics, subject-specific anthropometrics, a novel shoulder rhythm, glenohumeral stability ratios, hand forces, musculoskeletal geometry and an optimization routine to estimate joint reaction forces and moments, subacromial space dimensions, and muscle and tissue forces. The chimpanzee glenohumeral model consists of three modules – an external torque module, a musculoskeletal geometric module and an internal muscle force prediction module.

The purpose of this study was to develop a novel biomechanical and comparative chimpanzee glenohumeral model, designed to parallel an existing human glenohumeral model, and compare predicted musculoskeletal outputs between the two models. Coordination of these fields can allow different perspectives to contribute to a more complete interpretation of biomechanics of the modern human shoulder. Robust examination of behavioral shoulder performance and injury risk can be holistically improved through an interdisciplinary approach that integrates anthropology and biomechanics. Modern human shoulder function is affected by the evolutionary adaptations that have occurred to ensure survival and prosperity of the species.