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Patterns of clavicular bilateral asymmetry in relation to the humerus: variation among humans

Summary: Patterns of clavicular bilateral asymmetry in relation to the humerus:
variation among humans
Benjamin M. Auerbach a,*, Michelle H. Raxter b
Center for Archaeological Investigations, 3479 Faner Hall, Southern Illinois University, 1000 Faner Drive, Carbondale, Illinois 62901, USA
Department of Anthropology, University of South Florida, Tampa, Florida 33620, USA
Received 28 November 2006; accepted 1 October 2007
Studies of directional asymmetry in the human upper limb have extensively examined bones of the arm, forearm, and hand, but have rarely
considered the clavicle. Physiologically, the clavicle is an integrated element of the upper limb, transmitting loads to the axial skeleton and
supporting the distal bones. However, clavicles develop in a manner that is unique among the bones of the upper limb. Previous studies
have indicated that the clavicle has a right-biased asymmetry in diaphyseal breadth, as in humeri, radii, ulnae, and metacarpals, but unlike these
other elements, a left-biased length asymmetry. Few studies have assessed how clavicular asymmetry relates to these other bones of the upper
limb. Bilateral directional asymmetry of the clavicle is examined in relation to the humerus in a large, geographically diverse human sample,
comparing lengths and diaphyseal breadths. Dimensions were converted into percentage directional (%DA) and absolute (%AA) asymmetries.
Results indicate that humans have same-side %DA bias in the clavicles and humeri, and contralateral length %DA between these elements.
Diaphyseal breadths in both clavicles and humeri are more asymmetricdboth in direction and amountdthan lengths. Differences in diaphyseal
asymmetry are shown to relate to variation in physical activities among groups, but a relationship between activity and length asymmetry is not
supported. This further supports previous research, which suggests different degrees of sensitivity to loading between diaphyseal breadths and


Source: Auerbach, Benjamin M. - Department of Anthropology, University of Tennessee


Collections: Biology and Medicine