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


Anthropology, San Francisco State University

Friday Afternoon, Forum Suite Add to calendar

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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