The position of Australopithecus sediba within fossil hominin hand use diversity

Dunmore, Christopher J.; Skinner, Matthew M.; Bardo, Ameline; Berger, Lee R.; Hublin, Jean‐Jacques; Pahr, Dieter H.; Rosas, Antonio; Stephens, Nicholas B.; Kivell, Tracy L.

doi:10.1038/s41559-020-1207-5

Cited by 45 publications

(57 citation statements)

References 51 publications

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“…The morphology of the TMc complex of Kebara 2 suggests mechanical advantage when loading a more abducted thumb (Fig. 4), in agreement with current trabecular evidence 51 , suggesting a morphology favoring the use of "pad-topad" grips. This result is consistent with that of Karakostis et al 16 in which the Kebara 2 entheseal morphology suggests habitual use of precision grips.…”

Section: Pls1supporting

confidence: 81%

The implications of thumb movements for Neanderthal and modern human manipulation

Bardo

Moncel

Dunmore

et al. 2020

Sci Rep

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Much research has debated the technological abilities of Neanderthals relative to those of early modern humans, with a particular focus on subtle differences in thumb morphology and how this may reflect differences in manipulative behaviors in these two species. Here, we provide a novel perspective on this debate through a 3D geometric morphometric analysis of shape covariation between the trapezial and proximal first metacarpal articular surfaces of Neanderthals (Homo neanderthalensis) in comparison to early and recent humans (Homo sapiens). Results show a distinct pattern of shape covariation in Neanderthals, consistent with more extended and adducted thumb postures that may reflect habitual use of grips commonly used for hafted tools. Both Neanderthals and recent humans demonstrate high intraspecific variation in shape covariation. This intraspecific variation is likely the result of genetic and/or developmental differences, but may also reflect, in part, differing functional requirements imposed by the use of varied tool-kits. These results underscore the importance of holistic joint shape analysis for understanding the functional capabilities and evolution of the modern human thumb.

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Section: Pls1supporting

confidence: 81%

The implications of thumb movements for Neanderthal and modern human manipulation

Bardo

Moncel

Dunmore

et al. 2020

Sci Rep

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“…Finally, our ontogenetic analysis addresses evolutionary morphology but we do not directly investigate functional morphology in fossil species, since this would require the use of specific comparative functional (e.g., locomotion) data. The incorporation of analyses of functional morphology could evaluate/test the functional significance of our findings following 3 potential avenues for future research: (a) Biomechanical 3D models applied on early hominin fossils 74 , 75 , (b) trabecular morphology, widely used in functional morphology studies 76 – 78 , and (c) refined analysis of 3D muscle attachment sites (entheses) 79 , considering supportive experimental evidence involving laboratory animals 80 , 81 . Our work opens up a new window for addressing all these issues in fossil hominins from the Gran Dolina site in future studies.…”

Section: Discussionmentioning

confidence: 99%

Evolutionary development of the Homo antecessor scapulae (Gran Dolina site, Atapuerca) suggests a modern-like development for Lower Pleistocene Homo

García‐Martínez

Green

Castro

2021

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Two well-preserved, subadult 800 ky scapulae from Gran Dolina belonging to Homo antecessor, provide a unique opportunity to investigate the ontogeny of shoulder morphology in Lower Pleistocene humans. We compared the H. antecessor scapulae with a sample of 98 P. troglodytes and 108 H. sapiens representatives covering seven growth stages, as well as with the DIK-1-1 (Dikika; Australopithecus afarensis), KNM-WT 15000 (Nariokotome; H. ergaster), and MH2 (Malapa; A. sediba) specimens. We quantified 15 landmarks on each scapula and performed geometric morphometric analyses. H. sapiens scapulae are mediolaterally broader with laterally oriented glenoid fossae relative to Pan and Dikika shoulder blades. Accordingly, H. antecessor scapulae shared more morphological affinities with modern humans, KNM-WT 15000, and even MH2. Both H. antecessor and modern Homo showed significantly more positive scapular growth trajectories than Pan (slopes: P. troglodytes = 0.0012; H. sapiens = 0.0018; H. antecessor = 0.0020). Similarities in ontogenetic trajectories between the H. antecessor and modern human data suggest that Lower Pleistocene hominin scapular development was already modern human-like. At the same time, several morphological features distinguish H. antecessor scapulae from modern humans along the entire trajectory. Future studies should include additional Australopithecus specimens for further comparative assessment of scapular growth trends.

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“…Such bony markers of locomotor development could therefore be compared with other developmental milestones that track the overall pace of life history in fossil species. If the model presented in this paper holds up under longitudinal experimental conditions, trabecular structure can be used both to infer behavior from fossil morphology (Barak et al, 2013;Tsegai et al, 2013;Skinner et al, 2015;Kivell, 2016;Stephens et al, 2016;Bishop et al, 2018;Ryan et al, 2018;Sorrentino et al, 2019;Dunmore et al, 2020) and to serve as a valuable proxy for neuromuscular maturation and life history events like locomotor onset and the achievement of an adult-like gait.…”

Section: Discussionmentioning

confidence: 99%

“…The structure of spongy (trabecular) bone found inside bones is thought to be particularly responsive to mechanical stimuli Carter and Beaupré, 2001;Kivell, 2016). The link between mechanical loading and the three-dimensional structure of trabecular bone allows locomotor and postural behavior to be reconstructed in fossil taxa (Ryan and Ketcham, 2002;Skinner et al, 2015;Kivell, 2016;Stephens et al, 2016;Zeininger et al, 2016;Bishop et al, 2018;Ryan et al, 2018;Bardo et al, 2020;Dunmore et al, 2020). To understand how variation in trabecular structure arises within and between species, it is imperative to understand how it forms during growth and development (Ryan and Krovitz, 2006;Gosman and Ketcham, 2009;Ryan et al, 2017;.…”

Section: Introductionmentioning

confidence: 99%

Growth and development of trabecular structure in the calcaneus of Japanese macaques (Macaca fuscata) reflects locomotor behavior, life-history, and neuromuscular development

Saers

Gordon

Ryan

et al. 2021

Preprint

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We aim to broaden the analysis of bone structure by suggesting a new way to incorporate the interactions between behavior, neuromuscular development, and life-history. We examine the associations between these variables and age-related variation in trabecular structure in the calcaneus of Japanese macaques (Macaca fuscata). If skeletal markers linking these variables can be established, our inferences of the biology and behavior of fossil species would be significantly improved. We μCT scanned the calcaneus in a cross-sectional sample of 36 juveniles aged between 0 and 7 years old and 5 adults at the Primate Research Institute, Japan. We calculated whole bone averages of standard trabecular properties and generated whole-bone morphometric maps of bone volume fraction and Youngs modulus. Trabecular structure is increasingly heterogeneous in older individuals. BV/TV decreases during the first month of life and increases afterwards, coinciding with the onset of independent locomotion. At birth, primary Youngs modulus is oriented orthogonal to the ossification center, but after locomotor onset bone structure becomes stiffest in the direction of joint surfaces and muscle attachments. Age-related variation in bone volume fraction is best predicted by an interaction between neuromaturation, body mass, and locomotor independence. Results support the common assumption that trabecular structure dynamically adapts to novel joint loading conditions during ontogeny. The timing of independent locomotion, body size, and neuromuscular development, are all correlated to age-related variation in the trabecular structure of the macaque calcaneus. The causal mechanisms behind the observed patterns cannot be directly inferred from our cross-sectional study. If the model presented in this paper holds up under longitudinal experimental conditions, trabecular structure can be used both to infer behavior from fossil morphology and to serve as a valuable proxy for neuromuscular maturation and life history events like locomotor onset and the achievement of an adult-like gait.

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The position of Australopithecus sediba within fossil hominin hand use diversity

Abstract: The version in the Kent Academic Repository may differ from the final published version. Users are advised to check http://kar.kent.ac.uk for the status of the paper. Users should always cite the published version of record.

Cited by 45 publications

References 51 publications

The implications of thumb movements for Neanderthal and modern human manipulation

The implications of thumb movements for Neanderthal and modern human manipulation

Evolutionary development of the Homo antecessor scapulae (Gran Dolina site, Atapuerca) suggests a modern-like development for Lower Pleistocene Homo

Growth and development of trabecular structure in the calcaneus of Japanese macaques (Macaca fuscata) reflects locomotor behavior, life-history, and neuromuscular development

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