Evolutionary transformation of the hominin shoulder

Larson, Susan G.

doi:10.1002/evan.20149

Cited by 76 publications

(115 citation statements)

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“…3). This, in addition to the fossil evidence that early Miocene Apes were non-suspensory [Moyà-Solà et al, 2004;Ward, 2007], suggests that committed suspension, let alone brachiation, were probably not the basis of the hominoid ancestral locomotion [Moyà-Solà et al, 2004], so the idea of multiple emergences of suspensory characters during hominoid evolutionary history appears plausible [Almécija et al, 2007[Almécija et al, , 2009Larson, 1998Larson, , 2007Lovejoy et al, 2009a,b;Ward, 2007]. This region seems to be prone to homoplastic processes in primates, together with the aforementioned Ateles' morphological convergence with Pongo (Fig.…”

Section: General Considerationsmentioning

confidence: 88%

Shape analysis of the proximal humerus in orthograde and semi‐orthograde primates: Correlates of suspensory behavior

Arias-Martorell

Tallman

Potau

et al. 2014

American J Primatol

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"Suspensory locomotion" is an expression that encompasses a series of specialized forms of locomotion that mainly orthograde primates use to achieve below-branch traveling. It implies a number of features in the entire body associated with the use of the forelimb in overhead positions. The glenohumeral joint is one of the main joints involved in effective suspensory locomotion, being subject to a delicate balance between the high degree of mobility and stabilization needed to successfully engage in suspensory behaviors. Here, we present a 3D geometric morphometric study that explores the form of the proximal humerus of six orthograde and semi-orthograde genera (Hylobates, Pongo, Pan, Gorilla, Ateles, and Lagothrix) and a pronograde genus, Colobus, to determine to what extent suspensory locomotor requirements are driving the shape of this epiphysis. Results show the presence of a morphocline related to degree of suspension in the shape of the articular surface, with highly suspensory taxa (i.e., Hylobates) exhibiting particular morphological traits at the articular surface that provide a greater range of circumduction. The placement and orientation of the rotator cuff muscles' insertion sites on the tubercles appear associated with the divergent forces operating at the joint in quadrupedal or above-head use of the hand.

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Section: General Considerationsmentioning

confidence: 88%

Shape analysis of the proximal humerus in orthograde and semi‐orthograde primates: Correlates of suspensory behavior

Arias-Martorell

Tallman

Potau

et al. 2014

American J Primatol

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“…This is particularly interesting in light of the recent suggestion that anthropoid primate males and females have followed different hemisphere-specific evolutionary trends in the evolution of the prefrontal cortex [Smaers et al, 2012]. It is possible, on the other hand, that differences in thoracic shape and scapular position, rather than behaviour, are responsible for this dimorphism [Larson, 2007], but further studies are needed to explore this possibility. Due to the lack of significant differences in directional asymmetry in the current data for chimpanzees, and the lack of significance in left/right torsion frequencies in either sample, these interpretations must for now remain tentative, but future studies should explore the possibility of sexual differences in lateralization.…”

Section: Humeral Torsion Asymmetries In Humans and African Apesmentioning

confidence: 98%

Bilateral Asymmetry of Humeral Torsion and Length in African Apes and Humans

Barros¹,

Soligo²

2013

IJFP

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Few studies have directly compared human and African ape upper limb skeletal asymmetries despite the potential such comparisons have for understanding the origins of functional lateralization in humans and non-human primates. Here, we report the magnitude and direction of asymmetries in humeral torsion and humeral length in paired humeri of 40 Gorilla gorilla, 40 Pan troglodytes and 40 Homo sapiens. We test whether absolute and directional asymmetries differ between measurements, species and sexes. Our results show that humans are unique in being lateralized to the right for both measurements, consistent with human population-level handedness patterns, while apes show no significant directionality at the species level in either measurement. However, absolute torsion asymmetries in apes occur in the same magnitude as in humans, suggesting the existence of functional lateralization at the individual level.

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“…Interestingly, the later A. sediba has a more human-like shoulder compared with earlier A. afarensis, suggesting that the ancestor of A. sediba and Homo shared the more derived configuration. That said, it is not until the emergence of later Homo that a modern scapular configuration was largely in place (38,39). This final shift toward a fully lateralized spine and glenoid was likely costly to climbing efficiency and/or arm hanging (40), while also increasing shear stress at the shoulder and elevating the risk of rotator cuff injury (41,42).…”

Section: Nacholapithecus Sivapithecusmentioning

confidence: 99%

Fossil hominin shoulders support an African ape-like last common ancestor of humans and chimpanzees

Young

Capellini

Roach

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Reconstructing the behavioral shifts that drove hominin evolution requires knowledge of the timing, magnitude, and direction of anatomical changes over the past ∼6-7 million years. These reconstructions depend on assumptions regarding the morphotype of the Homo-Pan last common ancestor (LCA). However, there is little consensus for the LCA, with proposed models ranging from African ape to orangutan or generalized Miocene ape-like. The ancestral state of the shoulder is of particular interest because it is functionally associated with important behavioral shifts in hominins, such as reduced arboreality, high-speed throwing, and tool use. However, previous morphometric analyses of both living and fossil taxa have yielded contradictory results. Here, we generated a 3D morphospace of ape and human scapular shape to plot evolutionary trajectories, predict ancestral morphologies, and directly test alternative evolutionary hypotheses using the hominin fossil evidence. We show that the most parsimonious model for the evolution of hominin shoulder shape starts with an African apelike ancestral state. We propose that the shoulder evolved gradually along a single morphocline, achieving modern human-like configuration and function within the genus Homo. These data are consistent with a slow, progressive loss of arboreality and increased tool use throughout human evolution.geometric morphometrics | developmental simulation | phylomorphospace | scapula | rotator cuff T he human shoulder exhibits a unique combination of traits for a primate, a fact that has complicated previous attempts to reconstruct both its functional and evolutionary history. Notably, humans are most closely related to knuckle-walking/suspensory chimpanzees and bonobos (Pan or panins) (1, 2), yet morphometric analyses suggest that our shoulders are most similar in shape to that of the highly arboreal, quadrumanous orangutan (Pongo) (3-5). The hominin fossil record is similarly complicated. Scapular remains attributed to Australopithecus afarensis are described as similar to Gorilla (6-8) whereas the more recent Australopithecus sediba (MH2) displays morphometric affinities to both African apes (gorillas, chimpanzees, and bonobos) and Pongo (9). This mix of character states raises the question of whether modern human morphology reflects evolution from a more derived African ape morphology or retention of primitive traits from an earlier ape ancestor.A critical piece of evidence for solving this puzzle is the morphotype of the hominin-panin last common ancestor (LCA) (∼6-7 Mya). Although the fossil record near the hypothesized divergence time with Pan is the most direct means of addressing what the anatomy of the LCA shoulder was like, both hominin and African ape fossils from this time period are rare, fragmentary, and poorly understood (10, 11). Despite these difficulties, competing hypotheses about the LCA make explicit and mutually exclusive predictions of the direction, magnitude, and ordering of character transformations that we should observe in the fo...

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Evolutionary transformation of the hominin shoulder

Cited by 76 publications

References 91 publications

Shape analysis of the proximal humerus in orthograde and semi‐orthograde primates: Correlates of suspensory behavior

Shape analysis of the proximal humerus in orthograde and semi‐orthograde primates: Correlates of suspensory behavior

Bilateral Asymmetry of Humeral Torsion and Length in African Apes and Humans

Fossil hominin shoulders support an African ape-like last common ancestor of humans and chimpanzees

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