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

“产科困境”指的是人类婴儿的头部与其母亲的产道之间的紧密配合，这种比例失调导致难产和产妇死亡率。然而，人类并不是唯一经历过产科困难的灵长类动物。在一些体型较小的猴子物种中，记录到了严重的分娩并发症，如产妇或婴儿死亡，这些猴子的宝宝在出生时身体相对较大。这项博士论文研究验证了这一假设，即婴儿颅骨狭窄是一种进化适应，以缓解这些小体猴子的产科约束。通过加深我们对非人类灵长类动物产科限制的理解，以及这些物种如何应对它，我们也可能更好地理解人类产科困境的进化根源。该项目支持对职业生涯早期的女科学家进行研究和培训，并开发关于产科约束的演变以及产科和生殖保健必要性的教育单元。许多体型较小的新大陆猴子的头骨呈细长的形状，与人类和类人猿的球形形成鲜明对比。之前的研究表明，颅骨狭窄使这些物种能够生下大脑较大的婴儿，同时将难产的风险降至最低，这与人类产科的困境相似。相反，体型较小的东半球猴子成年后不会表现出颅骨狭窄，这种差异可以用产科约束的差异或出生后颅骨形状变化的物种间差异来解释。该项目分析了非人灵长类动物中产科约束与颅骨狭窄的相关性，并使用几何形态计量学跟踪了具有代表性的小体新世界和旧世界猴子物种从婴儿到成年生命阶段的颅形变化。研究人员综合了产科和发育形态学领域先前研究的方法，创建了灵长类产道的3D重建，并生成了对未来人类学研究有价值的婴儿灵长类CT扫描数据。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.