The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)


Effects of age-at-death, sex, body size and secular change on the biceps enthesis; a study of 3D surface areas

MONICA L. NOLTE and CYNTHIA WILCZAK.

Anthropology, San Francisco State University

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This study quantifies the degree to which body size, sex, age, and birth year (secular changes) influence the 3D rugose surface area of the biceps brachii insertion using a sample of 85 white individuals from the Robert J. Terry Collection. Entheseal surface areas were collected using a Nextengine ™ 3D scanner. The goal of the study is to contribute to the understanding of the relationship between biological variables, activity and enthesis morphology. Side-averaged results show that body size, as measured via the distal articular breadth of the humerus, accounts for 25% of the variation in male distal biceps entheseal area (n=48, r=.504 ) and 42% of the variation in female distal biceps entheseal area (n=37, r=.646 ).

The study sample was constrained to individuals aged 30 to 49. Even so, age-at-death explains approximately 33% of the variation in enthesis size for males (r=.577) and 8% of the variation for females (r=.284). Initial correlation results showed a strong relationship between birth year (range=1875-1934) and enthesis size for both sexes; however, Terry Collection males are unequally distributed by age-at-death across birth years. When age-at-death is controlled for using partial correlations, secular change results for males are non-significant. Among females year-of-birth explains 29% of the variation in rugose surface area once age-at-death is controlled for (r=-.541). Overall, size is the most significant variable for females, while age has a greater influence on 3D surface area of male entheses in this early 20th century American sample.

This study was funded by California State University Mini-grant and the Sacramento Archaeological Society.

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