The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Secular change in pelvic sexual dimorphism: a 3D study


Anthropology, University of Tennessee

Thursday 10, 301E Add to calendar

Research has shown that there is secular change occurring in the shape of the human bony pelvis. The pelvic canal has become more rounded with significant increases in the inlet AP diameter and the outlet transverse diameter. Because these changes are consistent across ancestries and sexes, environmental improvement (such as nutrition) rather than parturition is likely the cause. The question driving this research is whether sexual dimorphism is decreasing with the secular increases in these pelvic diameters.

The rearticulated bony pelvic girdles of individuals born between 1842 and 1981 were digitized for this study. Skeleton from the Hamann-Todd Osteological Collection, the Robert J. Terry Anatomical Skeletal Collection, and the William M. Bass Donated Collection were used. Individuals were placed into five birth cohorts made up of equal numbers of black and white, male and female. 3D coordinates were collected and measurements were calculated.

Geometric morphometry and traditional metrics indicated that the human pelvic shape has changed. The index of pelvic dimorphism revealed that for both blacks and whites, the transverse outlet diameter was the most dimorphic measurement followed by the inlet AP diameter. Whites showed a decreasing trend in sexual dimorphism in the inlet diameters and the AP outlet; however, these differences were not statistically significant. Blacks fluctuated in dimorphism, but this was also statistically insignificant. While secular changes are occurring in the human bony pelvis, there does not appear to be shift toward a uniform morphology. Females continue to maintain a form that is significantly different from males.

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