Doctoral Dissertation Improvement: Investigating the Obstetrical Dilemma: Patterns of Morphological Integration in the Primate Pelvis

现代人的出生是现存所有类人猿中最困难的，被认为是后来的古人类中两种相互竞争的选择力量妥协的结果：一种是允许高效的专职两足动物运动，另一种是允许大大脑和大身体的后代分娩--这是一种“产科困境”。过去的研究通过分析人类和其他类人猿之间的骨盆特征的平均值和比例来支持这一假说，这些差异被认为是过去对不同功能需求的选择压力的结果。此外，性状之间的相关性(即整合模式)也可能对选择做出反应，因此分析骨盆整合模式的种间差异为解决这一进化问题提供了一条新的途径。这个项目使用进化定量的方法来测试关于两足动物和产科的选择压力在人类骨盆形态进化中所扮演的角色的假设。它将重建人类骨盆中过去的选择压力，并定量确定两足行走和产科压力在导致人类物种之间的形态变化中所起的作用。这项研究揭示了被认为是适应两足或分娩的特征是否实际上是对其他特征选择的相关反应，而不是选择的直接产物。最后，这项研究测试了人类骨盆中的整合模式是否在与产科困境相关的相互冲突的选择压力下进化，以及这些模式在人类骨盆形态的演变中扮演了什么角色。除了进一步了解两足直立行走和生下大脑袋婴儿之间的权衡的进化两难境地，该项目还将促进共同PI在基于进化遗传学、生物学、统计学和生物人类学的跨学科方法中的培训，这可能提供关于进化生物学中关于整合模式在大规模适应中的作用以及它们促进进化变化的能力的更广泛问题的数据。对本科生的指导也有很多途径，允许他们参与不同层次的分析，并提供进行科学研究的实践经验。

Modern human birth is the most difficult of any living great ape, and is believed to be the result of a compromise between two competing selective forces in later hominins: one to allow for efficient obligate bipedal locomotion, and one to permit parturition of a large-brained and large-bodied offspring - the "obstetrical dilemma." Past studies have supported this hypothesis through analyses which compare means and proportions of pelvic traits between hominins and other apes, differences that are believed to be the result of past selection pressures for divergent functional requirements. In addition, correlations between traits (i.e. patterns of integration) may also respond to selection, and thus analyzing interspecific differences in pelvic patterns of integration provides a new route to addressing this evolutionary problem. This project uses evolutionary quantitative methods to test hypotheses about the roles that selection pressures for bipedalism and obstetrics have played in the evolution of hominin pelvic morphology. It will reconstruct past selection pressures in the pelves of hominins and quantitatively determine the roles that pressures for bipedalism and obstetrics played in causing the morphological changes seen across species of hominins. The research reveals if traits thought to be adaptations for bipedalism or parturition are actually correlated responses to selection on other traits rather than having been direct products of selection. Finally, the research tests if patterns of integration in the pelves of humans have evolved in response to conflicting selection pressures relating to the obstetrical dilemma and what role these patterns have played in the evolution of hominin pelvic morphology. In addition to furthering understanding of the evolutionary dilemma of the trade-offs between walking upright bipedally and giving birth to large-brained infants, this project will further the co-PI's training in an interdisciplinary approach based in evolutionary genetics, biology, statistics, and biological anthropology, which may provide data on broader questions in evolutionary biology relating to the role of patterns of integration in large-scale adaptations, as well as their ability to facilitate evolutionary change. There are also many avenues for the mentoring of undergraduates, allowing them to participate in different levels of analyses and providing hands-on experience in conducting science.