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

Estimating variance in femoral head size against body mass estimation: implications for evolution and integration


Department of Anthropology, The University of Tennessee

March 26, 2015 , Gateway Ballroom 2 Add to calendar

Auerbach and Ruff’s 2004 study showed correspondence in mechanical and morphological approaches to estimating body mass in humans. However, approximately 40% of the variance between estimations is unexplained, and small-mass groups have large femoral heads for their expected masses. Subsequent research indicates that femoral head size does not ontogenetically match body mass, but rather follows growth in femoral length (Ruff, 2007). Thus, while femoral head size mechanically relates to body mass, these prior results collectively indicate that underlying covariance between femoral length (a major component in morphological body mass estimates) and femoral head size may be driving the correspondence between the two body mass estimation methods.

Here, resampling methods are used to compare variance in femoral head diameter (FHD) within groups against morphological body mass estimates (MorBMEs) and femoral lengths (FMLs). In each of 20 groups in the Goldman Data Set, mean FHDs MorBMEs, and FMLs, standardized by the dimension, were calculated from subsamples for 1000 iterations. The distributions of these were then compared using parametric methods. Results show that the distributions of FHDs significantly differ from MorBMEs, and that the differences between the distributions of these dimensions are stochastic among groups. In contrast, FHD distributions are not consistently different from FML distributions. Femoral head size varies independently of MorBMEs within groups, while FHD and FML are less independent. MorBME, then, may correspond well with FHD body mass estimates largely due to covariance between the femoral dimensions. Further implications for morphological integration and evolution among small-mass human groups are considered.

Funding from the Joanna Jackson Goldman Memorial Prize and National Science Foundation DDRIG BCS#0550673