Solving the evolutionary puzzle of human childbirth 

Staff: Lia Betti, Todd C. Rae 

Humans are unique among the great apes in having a tight birth canal and a relatively high risk of feto-pelvic disproportion, when the baby is too big to progress though the canal. Our childbirth difficulties have long been explained by the selection of a narrow pelvic canal for efficient bipedal locomotion. However, recent studies have shown that this explanation does not stand up to scrutiny and that other primates experience similar obstetric problems. In this project, we will compare the 3D morphology of the pelvis across a large number of primate species to investigate how the combination of selective pressures due to locomotion, habitual posture (orthograde or pronograde) and relative neonatal size have shaped the pelvis across primates, leading to difficult births in humans as well as a few other primates. 


3D models of a chimpanzee (left) and a human (right) pelvis reconstructed from CT-scan images. Landmarks for shape analyses have been added to the chimpanzee pelvis. 



2The frontispiece to Huxley’s Evidence as to Man’s Place in Nature (1863). The image compares the skeletons of humans to other apes.