Elastic energy storage in the shoulder and the evolution of high-speed throwing in Homo

Roach, Neil T.; Venkadesan, Madhusudhan; Rainbow, Michael J.; Lieberman, Daniel E.

doi:10.1038/nature12267

Cited by 230 publications

(174 citation statements)

References 33 publications

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“…3). This gradual shift in spine and glenoid angle affects the fiber orientation of the pectoral and scapular muscles, altering the position of the upper limb where force production is optimized (34). The reduced, caudally shifted angle in Homo is consistent with both a decreased reliance on use of the upper limb for overhead actions, such as climbing, and the increased use of…”

Section: Discussionmentioning

confidence: 85%

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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Section: Discussionmentioning

confidence: 85%

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.

Self Cite

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“…Wilk et al (Wilk et al, 1993) argued that throwing athletes enhance torque production by 'pre-stretching' numerous throwing muscles just prior to their activation, resulting in elastic energy storage in the muscle itself. In addition, Roach et al (Roach et al, 2013) found that the posture of the 'cocked' arm (externally rotated) just prior to the rapid shoulder internal rotation motion passively stretches elastic elements crossing the shoulder. By comparing actual power production during throwing to modeled maximum power values for all muscles potentially involved, they inferred that passive stretching results in significant amounts of elastic energy being stored and released, powering the rapid internal rotation of the humerus that follows.…”

Section: Research Articlementioning

confidence: 99%

“…This should significantly reduce torso rotation angular velocity, torque, power and work. These reductions, however, are expected to be modest because we are limiting rotational motion only between the vertebrae and not at the hips.Hypothesis 2: torso rotation primarily powers the storage of elastic energy at the shoulder Roach et al (Roach et al, 2013) proposed that by abducting the shoulder and flexing the elbow as torso rotation reaches its peak …”

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confidence: 99%

Upper body contributions to power generation during rapid, overhand throwing in humans

Roach

Lieberman

2014

Journal of Experimental Biology

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High-speed and accurate throwing is a distinctive human behavior. Achieving fast projectile speeds during throwing requires a combination of elastic energy storage at the shoulder, as well as the transfer of kinetic energy from proximal body segments to distal segments. However, the biomechanical bases of these mechanisms are not completely understood. We used inverse dynamics analyses of kinematic data from 20 baseball players fitted with four different braces that inhibit specific motions to test a model of power generation at key joints during the throwing motion. We found that most of the work produced during throwing is generated at the hips, and much of this work (combined with smaller contributions from the pectoralis major) is used to load elastic elements in the shoulder and power the rapid acceleration of the projectile. Despite rapid angular velocities at the elbow and wrist, the restrictions confirm that much of the power generated to produce these distal movements comes from larger proximal segments, such as the shoulder and torso. Wrist hyperextension enhances performance only modestly. Together, our data also suggest that heavy reliance on elastic energy storage may help explain some common throwing injuries and can provide further insight into the evolution of the upper body and when our ancestors first developed the ability to produce high-speed throws.KEY WORDS: Throwing, Biomechanics, Elastic energy storage, Kinetic chain, Human evolution INTRODUCTIONThe human forelimb is derived relative to other hominoids and to earlier hominins (Larson, 1993;Larson, 2007). One reason the human shoulder may be so different is selection for humans' unique ability to throw objects overhand with both accuracy and high velocity. Today, most high-speed throwing occurs during sports, but in the past throwing was probably crucial for hunting, defense against predators, and aggressive interactions. Regardless of their purpose, high-speed overhand throws are produced using a stereotypic, whip-like motion involving the whole body.The throw begins with movement of the legs and progresses quickly up the trunk and arm, ending with rapid movement of the throwing hand as the projectile is released. There has been considerable inquiry into how this complex motion generates high projectile velocities, and which joints and joint-specific angular motions are primarily responsible Fleisig et al., 1995;Hirashima et al., 2007;Hirashima et al., 2008;Hong et al., , 1985;Putnam, 1993). Previous work has shown that large angular velocities of torso rotation, shoulder internal rotation, elbow extension and wrist flexion all occur at the moment of release and significantly contribute to projectile speed ( Fig. 1) (Fleisig et al., 1995;Fleisig et al., 1996;Hirashima et al., 2007;Pappas et al., 1985). This study focuses on how these large angular velocities are produced in the upper body. RESEARCH ARTICLEAngular movements are produced when torques act across joints, generating mechanical work and power. Muscles are the source of...

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“…The final changes (e.g. fully lateral glenoid position) that enhanced the storage and release of elastic energy in the shoulder to enable high-speed throwing appeared in H. erectus 2 Mya (Roach et al, 2013). Ballistic throwing would have provided H. erectus with enhanced hunting ability and possibly knapping efficiency.…”

Section: Dedicated Tool Manipulation Morphologymentioning

confidence: 99%

A complex adaptive system may be essential for cumulative modifications in tool design

Hunt¹,

Uomini

2016

Japanese Journal of Animal Psychology

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The cumulative modification of tool designs over time is a crucial development for technological evolution. Cognitive-related prerequisites for this technological capability are innovative behaviour and the faithful inter-generational transmission and maintenance of tool designs by accurate social learning processes. Here, we investigated the hypothesis that a complex of morphological and behavioural adaptations specifically for tool skills is also required. In a novel analysis we compared the tool-associated adaptive patterns in Homo erectus and the New Caledonian crow. Both species provide the most convincing early Homo and nonhuman evidence, respectively, for the making of cumulatively modified tools. We identified probable shared traits in H. erectus and the New Caledonian crow that include morphological adaptations specifically for enhanced tool manipulation and a significant component of daily diet from hunting and/or processing animal food with tools. We propose that a tool-using lifestyle based on animal food that confers a reproductive advantage and evolves enhanced tool manipulation skills, together with appropriate innovative ability and social learning processes, may be essential for cumulative modification of tool designs.

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Elastic energy storage in the shoulder and the evolution of high-speed throwing in Homo

Cited by 230 publications

References 33 publications

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

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

Upper body contributions to power generation during rapid, overhand throwing in humans

A complex adaptive system may be essential for cumulative modifications in tool design

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