Morphological Integration of the Human Pelvis with Respect to Age and Sex

Considerable research has shown that modern human pelvic dimensions, especially of the birth canal, are sexually dimorphic. Studies also suggest that females with younger ages-at-death have narrower canal dimensions than those who die at older ages, possibly due to continued independent growth of the pubis. A recent examination of this pattern argued that it is unlikely that these differences relate to mortality, but the source of the difference in pelvic dimensions with age remains unresolved. We use pelvic dimensions to assess differences in magnitudes of morphological integration between adult females and males across ages-at-death. We first ascertain whether the sexes have different strengths of integration, and then assess if differences in magnitudes of integration are associated with age-at-death. Pelvic dimensions of all groups were moderately integrated. Females and males have similar magnitudes of integration, and there is no change in the strength of integration with age. Examining individual regions of the pelvis indicates that the ilium, pubis, and pelvic inlet and outlet have stronger integration than the overall pelvis. This was particularly true of the pelvic outlet, which demonstrated the strongest integration. Our findings suggest that regions of the pelvis are more strongly integrated internally, and less integrated with each other, which would allow for proportional growth among regions of the pelvis with age that do not affect its overall integration. No single region of the pelvis appears to be motivating the difference in pelvic dimensions between age groups. We further consider the implications of these findings on evolutionary constraints. Anat Rec, 300:666-674, 2017. © 2017 Wiley Periodicals, Inc.