Master of Arts (MA)
Geography and Anthropology
The unique configuration of the human clavicle and mastoid process suggests a functional connection between the head and shoulders in humans. The hypothesis in this study is that the clavicle, scapula and head form a functional complex and are interconnected by the sternocleidomastoid and trapezius muscles. In this complex, the trapezius muscles attach to the skull and become active when loads are carried. The sternocleidomastoid muscles are anchored to the clavicles; when loads are being carried, they act as guy ropes for the head, thereby keeping the head from being extended by the force of the contracting trapezius muscles. These muscle actions can be expected to leave evidence on the bones to which they attach, and this evidence could be measurable. The hypothesis was tested by comparing the mensural and morphological bilateral asymmetries of 15 skeletal features, most of which would likely be affected by the functioning of this complex in individuals. The hypothesis is supported by the results which show that four character pairs of the functional complex (i.e., rise of the superior nuchal line, width of the mastoid, breadth of the scapula, diameter of the humerus) display significant directional asymmetry in right-handed individuals; the sample size of left-handed individuals was too small to provide meaningful results.
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Osborn, Michelle Lynn, "Effects of handedness on the skull and shoulder bones" (2008). LSU Master's Theses. 1342.
Tague, Robert G.