Does bipedal locomotion create an obstetrical dilemma?

The tight fit, and occasional misfit, between the baby and the maternal birth canal can create a considerable health risk for the mother and the child. It is well known, that women with narrower pelvic dimensions have higher incidence of obstructed labour but it is not clear why this problem has not been corrected in the evolution of our species. Although the demands of bipedal locomotion have long been assumed responsible for the maintenance of the narrow pelvis in humans, to date, this hypothesis has not received any experimental support. The proposed project will carry out a rigorous test of how bipedal locomotion might have created selective pressure for the small pelvic size in humans. I hypothesise that not only the width of the pelvis but further details of the geometry of the pelvic girdle affect joint reaction forces at the hip, as well as metabolic energy consumption and powers generated during the bipedal gait. Using a novel combination of state-of-the-art morphometric and biomechanical methods, I will carry out statistical analysis of the relationship between pelvis and hip geometry and compare results with kinematic and dynamic gait analyses of the bipedal walking. This study will generate MRI and kinematic data with the help of a large cohort of healthy volunteers and will also use gait analysis results previously collected by medical practitioners. To generate the large statistical sample for the 3D hip and pelvis geometry, I will additionally involve an open-access collection of CT scans of deceased individuals. I intend to determine which details of the pelvic girdle geometry are responsible for higher joint reaction forces in humans and which may create energy disadvantages during the bipedal locomotion. My hypotheses will be confirmed if these details are related to the size of the birth canal in women. Ultimately, this project will link the fields of anthropology, evolutionary biology and gender medicine, bridging between biological theory and medical practice. For the first time, I will generate a significant set of data to assess the role of bipedal locomotion in the maintenance of the narrow pelvis in humans. My results will bring an improved understanding of the sex-specific interactions between pelvic dimensions and the biomechanics of locomotion. New sex-specific models for calculating joint reaction forces in orthopaedic patients will be put in open access. A set of sex- specific morphological parameters will be created for orthopaedic planning.