Doctoral Dissertation Improvement: Bipedal Obstetric Load and the Evolution of Human Lumbopelvic Sexual Dimorphism

发育中的胎儿改变母体的身体比例和质量分布，导致脊柱和骨盆不稳定。 本研究假设，人类腰椎和骨盆解剖的性别二型性，部分代表了独特的女性适应胎儿负荷的生物力学相关的结构风险。 这一假说与普遍的观点不同，即腰盆性别二型完全与分娩选择有关，分娩选择有利于产妇产道足够宽敞，以分娩大脑或大身体的新生儿。 作为一个框架来解释人类lumbopelvic性别二型性的范围，目前的结论可能是有限的，只集中在骨盆形态直接相关的分娩事件，并没有考虑随之而来的压力的生殖负荷。腰椎和骶椎的性别二态性一直被解释为与骨盆相适应，这掩盖了椎骨在躯干生物力学中执行更直接功能的可能性。 虽然妊娠是间歇性的，但胎儿负荷的持续时间和重复对姿势和运动骨骼产生显著的压力，不仅对现代人类，而且对早期的两足动物也有影响。 将在70名人类女性和70名人类男性以及13种非人灵长类动物（包括习惯性直立的灵长类动物）的600名个体的比较样本中，对腰盆骨骼的性二型进行形态计量学检查，以检查人类的腰盆性二型大于其他灵长类动物的预测。 为了研究人类胎儿负荷对腰骨盆骨骼的生物力学影响，将从运动学上确定20名孕妇的脊柱负荷模式，包括母体质心位置、下背部曲线和骨盆前倾角。 实验方法将测试假设的重量重新分配和负载的人类女性脊柱和骨盆在怀孕期间，而比较形态学的方法将这些结果纳入更广泛的系统发育和进化背景。 该项目的广泛影响有三个方面。 首先，重建自适应模式在双足产科负荷将提供进化的深度，目前由临床实践定义的人类经验。 第二，这项研究将为本科生助理提供实践研究经验，他们将获得项目管理方面的学术和实践培训。 第三，由于志愿者参与这项研究，女性公众和学术界之间的互动将有助于促进妇女参与当前的研究，并最终为妇女的生活教育提供信息。

A developing fetus modifies maternal body proportions and mass distribution introducing instability to the vertebral column and pelvis. This study hypothesizes that human sexual dimorphism of lumbar vertebral and pelvic anatomy represents, in part, unique female adaptations to structural risks associated with biomechanics of fetal load. The hypothesis differs from the prevailing view that lumbopelvic sexual dimorphism is entirely related to parturitional selection favoring a maternal birth canal spacious enough for delivery of a large-brained or large bodied neonate. As a framework for interpreting the scope of human lumbopelvic sexual dimorphism, current conclusions may be limited by focusing only on pelvic morphology directly related to the birthing event and by failure to consider the attendant stresses of reproductive load. Persistent interpretation of sexual dimorphism in lumbar and sacral vertebrae as compliant to the pelvis obscures the possibility that the vertebrae perform a more immediate function in trunk biomechanics. Although pregnancy is intermittent, the duration and recurrence of fetal load exert marked stress on the postural and locomotor skeleton, holding implications not only for modern humans but for earlier bipeds as well. Sexual dimorphism of the lumbopelvic skeleton will be examined morphometrically in 70 human females and 70 human males and in a comparative sample of 600 individuals of 13 species of nonhuman primates, including habitually erect taxa, to examine the prediction that lumbopelvic sexual dimorphism is greater in humans than in other primates. To investigate the biomechanical impact of human fetal load on the lumbopelvic skeleton, spinal loading patterns of twenty pregnant females will be kinematically identified for position of the maternal center of mass, curve of the lower back and angle of anterior pelvic tilt. The experimental approach will test hypotheses on weight redistribution and loading of the human female spine and pelvis during pregnancy; while the comparative morphometric approach will place these results into broader phylogenetic and evolutionary contexts. The wider effects of this project are threefold. First, reconstruction of adaptive patterns in bipedal obstetric load will provide evolutionary depth to a human experience currently defined by clinical practice. Second, the study will provide hands-on research experience for undergraduate assistants who will gain both academic and practical training in project management. Third, as a result of volunteer participation in this study, interactions between the female public and the academic community will help to advance women's access to current research and will ultimately inform the life education of women.