The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)


Neck-Shaft Angle and Climate-Induced Body Proportions

STEPHANIE L. CHILD and LIBBY W. COWGILL.

Anthropology, University of Missouri

March 27, 2015 , Archview Ballroom Add to calendar

There is considerable temporal and geographic variation in femoral neck-shaft angle (NSA). Traditionally, a lower NSA is linked to an increased level of physical activity during life. More recently, however, research suggests that lower NSA might also be explained, in part, as the mechanical consequence of differences in ecogeographic body proportions. This study tests the proposed link between climatic-induced body proportions and NSA through the course of development in a sample of geographically diverse children. Data suggest that starting at a very early age, there is a significant interaction between NSA and body mass and shape, and that this relationship differs among children with different body proportions. These results, combined with other studies, suggest a mechanical interaction between proximal hip geometry and the changing angle of hip joint reaction forces during development. The functional significance of this, both in terms of evolutionary change and developmental plasticity, is that variation in body proportions alter the angulation of applied loads across the proximal metaphysis in the developing femur, thereby resulting in differing adult NSA. This study highlights the importance of the angulation and distribution of mechanical loading in the skeletal adaptation of the femur.