Pelvic Shape and Differential Mortality: Obstetric Variation Among Indigenous North American Populations

University Of Tennessee Knoxville, Knoxville TN

Investigators

Abstract

This research examines the association of pelvic dimensions and natural selection as it relates to both age-at-death in females and climate among past indigenous North American groups. The investigators predict that narrow pelvic inlets in females, a measure of obstetric efficiency (the ability to give birth without complications) will have caused higher death rates in young aged individuals. In addition, previous studies have linked pelvic shape, especially hip breadth, to body heat regulation. Individuals with wider bodies have less surface area relative to body mass, and therefore are more efficient at retaining body heat. Indigenous North Americans have been shown to possess wider bodies than would be expected for the latitudes in which they lived. Thus, their body shape may be related to common ancestral occupation of colder climates, a trait then shared by descendent populations. Although climate may have selected for narrower bodies in warmer climates, obstetric efficiency may have attenuated this pressure. Although multiple factors are related to the age at which individuals died, a correlation between young aged mean mortality and narrow dimensions in the pelvic outlet would support pelvic shape and obstetrical complications as a selective factor among females. Furthermore, if the shape of the pelvic outlet covaries with overall hip breadth, this would indicate that pelvic shape is indeed a balance between at least two selective pressures: climate and obstetrics. Broadly, this project contributes to the understanding of biological changes encountered by migrating humans and factors influencing those changes. It contributes further to an understanding of body shape variation among humans. The study will incorporate pre-doctoral students in data collection at major skeletal repositories and encourages students toward the development of further studies. Furthermore, new methods for capturing and comparing shape data, developed in collaboration with a postdoctoral researcher at the Max Planck Institute in Leipzig, will be created and shared with other researchers.