Doctoral Dissertation Research: Selection pressures on skull and pelvis proportions at birth

Being born is a process all humans must experience; however, even with modern medical intervention, it is risky and potentially fatal for both mother and infant. This doctoral dissertation project examines the evolution of skull and pelvis shape in a wide range of monkeys and apes to better understand how and when birthing difficulties may have arisen in different primate lineages, and better determine whether the difficulties faced by humans are unique to our species or a legacy shared by our taxonomic order. This project fosters graduate student training of a female scientist and can provide a deeper understanding of the difficulty of human childbirth for medical professionals. Results of this research are communicated to the public through popular science outlets. Due to the tight fit between the birth canal and the infant skull, modern human childbirth is more dangerous and more likely to result in death for the infant or mother than in other large-bodied apes like chimpanzees and gorillas. As a result, difficult childbirth has historically been thought of as an evolved trait unique to humans, possibly stemming from the combination of pelvic adaptations to walking upright and the evolution of unusually large brains. However, smaller-bodied primates, such as the lesser apes and some monkeys, have been reported to experience serious complications, including maternal and infant death, during labor. This raises questions about whether humans experience difficult births for the same reason as smaller-bodied primates, or if difficult birth in humans is, in fact, unique. To address this question, this project investigates patterns of evolution and natural selection in the primate skull and pelvis, particularly in regions critical to childbirth, using 3D scan data to compare the patterns and magnitude of shape differences in the skull and pelvis to those expected based on genetic relationships among a wide sample of ape and monkey species. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.