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

Secular change and the modern human pelvis


Anthropology, University of Tennessee, Knoxville

Saturday 4, Forum Suite Add to calendar

Secular changes in growth in the United States are well documented; this is also true for neonates. Full-term babies have exhibited a positive trend in birth weight, length, and head circumference. The question driving this research was whether the adult bony pelvis is changing in concert with the neonatal head. Likely, the modern morphology of the human pelvic girdle is a compromise between locomotion and parturition; has this form changed to accommodate successful birth?

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 calculated.

Geometric morphometry and traditional metrics indicated that the shape of the pelvis has changed. The pelvic canal is more rounded with significant increases in the inlet AP diameter and the outlet transverse diameter. Also, the subpubic angle is significantly larger in later birth cohorts. Females did not show corresponding increases in inlet transverse or outlet AP diameters. There is secular change occurring in the human bony pelvis. However, since the changes are consistent across ancestries and sexes, environmental improvement, such as nutrition, rather than parturition is likely the cause. Understanding the secular changes that alter the human pelvis will aid in deciphering how and why the current form exists.

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