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Trabecular bone structure of the proximal capitate in extant hominids and fossil hominins with implications for midcarpal joint loading and the dart‐thrower's motion
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2024-02-16
Submitted Date
2022-10-12
Subject Terms
African apes
Australopithecus
cancellous bone
fossil Homo
wrist
Australopithecus
cancellous bone
fossil Homo
wrist
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Abstract
Objectives
This research examines whether the distribution of trabecular bone in the proximal capitates of extant hominids, as well as several fossil hominin taxa, is associated with the oblique path of the midcarpal joint known as the dart‐thrower's motion (DTM).
Materials and Methods
We analyzed proximal capitates from extant (<jats:italic>Pongo n</jats:italic> = 12; <jats:italic>Gorilla n</jats:italic> = 11; <jats:italic>Pan n</jats:italic> = 10; fossil and recent <jats:italic>Homo sapiens n</jats:italic> = 29) and extinct (<jats:italic>Australopithecus sediba n</jats:italic> = 2; <jats:italic>Homo naledi n</jats:italic> = 1<jats:italic>; Homo floresiensis n</jats:italic> = 2; Neandertals <jats:italic>n</jats:italic> = 3) hominids using a new canonical holistic morphometric analysis, which quantifies and visualizes the distribution of trabecular bone using relative bone volume as a fraction of total volume (rBV/TV).
Results
Homo sapiens and Neandertals had a continuous band of high rBV/TV that extended across the scaphoid, lunate, and hamate subarticular regions, but other fossil hominins and extant great apes did not. <jats:italic>A. sediba</jats:italic> expressed a distinct combination of human‐like and <jats:italic>Pan</jats:italic>‐like rBV/TV distribution. Both <jats:italic>H. floresiensis</jats:italic> and <jats:italic>H. naledi</jats:italic> had high rBV/TV on the ulnar‐side of the capitate but low rBV/TV on the radial‐side.
Conclusion
The proximal capitates of <jats:italic>H. sapiens</jats:italic> and Neandertals share a distinctive distribution of trabecular bone that suggests that these two species of <jats:italic>Homo</jats:italic> regularly load(ed) their midcarpal joints along the full extent of the oblique path of the DTM. The observed pattern in <jats:italic>A. sediba</jats:italic> suggests that human‐like stress at the capito‐scaphoid articular surface was combined with <jats:italic>Pan</jats:italic>‐like wrist postures, whereas the patterns in <jats:italic>H. floresiensis</jats:italic> and <jats:italic>H. naledi</jats:italic> suggest their midcarpal joints were loaded differently from that of <jats:italic>H. sapiens</jats:italic> and Neandertals.
Citation
: Bird, E. E., Kivell, T. L., Dunmore, C. J., Tocheri, M. W., & Skinner, M. M. (2024). Trabecular bone structure of the proximal capitate in extant hominids and fossil hominins with implications for midcarpal joint loading and the dart-thrower's motion. American Journal of Biological Anthropology, 183(3), e24824. https://doi.org/10.1002/ajpa. 24824
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Copyright © 2023 The Authors. American Journal of Biological Anthropology published by Wiley Periodicals LLC. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. The attached file is the published version of the article.
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2692-7691
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2692-7691