Doctoral Dissertation Research: Obstetric constraints on neurocranial shape in nonhuman primates

Suny At Stony Brook, Stony Brook NY

Investigators

Abstract

The “obstetric dilemma” refers to the tight fit between a human infant’s head and its mother’s birth canal, a disproportion that contributes to difficult labor and maternal mortality. However, humans are not the only primates to experience obstetric difficulties. Birth complications as severe as maternal or infant death have been recorded in some small-bodied monkey species, whose babies have relatively large bodies during birth. This doctoral dissertation research tests the hypothesis that infant cranial narrowness is an evolutionary adaptation to mitigate obstetric constraint in these small-bodied monkeys. By deepening our understanding of obstetric constraint in nonhuman primates, and how these species cope with it, we may also better understand the evolutionary roots of the human obstetric dilemma. This project supports the research and training of an early-career female scientist and development of educational modules on the evolution of obstetric constraint and the necessity of obstetric and reproductive healthcare. Many small-bodied new-world monkeys exhibit a long and narrow skull shape, in contrast to the globular shape observed in humans and apes. Previous research suggests that cranial narrowness allows these species to give birth to large-brained infants while minimizing the risk of obstructed labor, drawing parallels to the human obstetric dilemma. Conversely, small-bodied old-world monkeys do not exhibit cranial narrowness as adults, a disparity that could be explained by variation in obstetric constraints or by interspecies differences in how cranial shape changes after birth. This project analyzes the correlation between obstetric constraint and cranial narrowness in nonhuman primates and uses geometric morphometrics to track cranial shape change from infant to adult life stages in representative species of small-bodied new-world and old-world monkeys. The investigators synthesize methods from prior research in the fields of obstetrics and developmental morphology to create 3D reconstructions of the primate birth canal and generate infant primate CT scan data valuable to future anthropological research. 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.