The influence of climate on the obstetrical dimensions of the human bony pelvis

by Nuger, Rachel Leigh, Ph.D., CITY UNIVERSITY OF NEW YORK, 2008, 157 pages; 3297000


The human bony pelvis is thought to be under the influence of several different selective pressures: locomotor constraints imposed by habitual terrestrial bipedalism, obstetric constraints imposed by the birth of large-brained, broad-shouldered neonates, and climatic pressures that have an influence on body breadth, and perhaps pelvic breadth specifically. This dissertation focuses on the latter two selective pressures by investigating the relationship between obstetrics and climate and the subsequent impact that these two pressures may have on pelvic morphology. This study investigated the relationships and degree of variation in pelvic morphology both within and across human populations representing different climatic regimes to determine if there are associations between obstetrics and climate.

Pelvic and long bone measurements from adult human skeletal remains representing diverse climatic regimes were collected. Partial correlation analysis was used to determine the extent of ecogeographical patterning across the samples. Body size was adjusted for using the anteroposterior (AP) femoral head diameter as the covariate in partial correlation analysis. A variety of approaches to quantifying climate were utilized.

The results of this study indicated that in females, the major transverse pelvic obstetrical diameters (the diameters at the plane of the pelvic inlet, midplane, and outlet) were statistically significantly correlated with climate. These results indicated larger obstetrical pelvic dimensions in high latitude/cold climate female individuals and smaller obstetrical pelvic dimensions in low latitude/hotter climate female individuals. The results for anteroposterior (AP) pelvic dimensions were not as consistent, and most AP pelvic obstetrical dimensions were not statistically significantly correlated with climate. Results were similar for males, with the exception of the transverse pelvic inlet which was not correlated with climate, and some additional AP pelvic dimensions that were not significant in females.

These results suggest that there is a statistically significant relationship between transverse obstetrical pelvic diameters in climate. Furthermore, this relationship remains significant even after accounting for individual body size. The transverse pelvic obstetrical dimensions exhibit a greater degree of ecogeographic patterning than AP pelvic obstetrical dimensions, perhaps because of biomechanical constraints, or because AP pelvic diameters are oriented in a superoinferior direction when the pelvis is in anatomical position.

AdviserSara Stinson
Source TypeDissertation
SubjectsMorphology; Physical anthropology; Obstetrics
Publication Number3297000

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