Socio-Ecologic Modulators of Human Females' Reproductive Maturation and Senescence: A Life History Approach

雌性根据环境的物理条件，如死亡风险和资源的质量和可用性，调整生殖策略。然而，对智人来说，社会条件在繁殖中也起着关键作用。我的长期目标是开发一个综合模型，整合影响人类女性一生中生殖轨迹的所有社会生态因素。我之前研究过雌性在生殖阶段（第一次分娩到最后一次分娩）的生殖适应，我的短期目标是研究哺乳动物雌性的两个罕见的生殖特征：异常漫长、生育不足的生殖过渡，结束了它们的生殖寿命：a)初潮到第一次分娩，b)围绝经期到绝经期。这些转变在发生的时间、持续时间和生育水平方面在种群内部和种群之间表现出明显的差异。我推测，这种差异是直接适应和间接适应之间复杂权衡的结果，这些适应与向近亲（生殖成熟前的兄弟姐妹、侄女和侄子；更年期的子女和孙子）提供异母照顾有关。方法：为了实现我的目标，我将继续我在2000年开始的107名危地马拉卡奇奎尔玛雅母亲和100名她们的女儿的队列研究。为了研究生殖成熟和衰老，我将在2019/20年度通过人体测量评估、月经日记和生殖生物标志物量化来监测其生殖状态的年龄相关变化。社会生态条件在社区和个人层面的作用将通过社会、人口、饮食和资源可用性访谈以及发病率和死亡率风险数据进行评估。个体的能量状态和生理应激水平将通过饮食日记和尿液生物标志物的量化来监测。我将把这些信息与我自2000年以来从同一个人那里收集到的数据结合起来。影响：该研究将产生迄今为止最完整的前瞻性数据集，以调查在传统的、自给自足的、自然生育的人口中，人类女性如何根据其累积的社会生态环境调整其生殖策略。我的研究结果也将进一步加深我们对社交网络对女性生殖发育和衰老的作用的理解。在这两种罕见的生殖转变中，人类女性在直接和间接适应之间的权衡所获得的知识，都应该为塑造人类女性生殖生活史的选择过程提供新的理论见解，并指导对其他合作繁殖物种的类似现象的研究。

Females adjust their reproductive strategies according to their environments' physical conditions, such as mortality risks and resource quality and availability. In Homo sapiens, however, social conditions also play a critical role in reproduction. My long-term goal is to develop a synthetic model that integrates all socio-ecological factors affecting human females' reproductive trajectories across their lifespan. Having previously studied female reproductive adaptations during the reproductive phase (first to last birth), my short-term goal is to study two rare reproductive traits for mammalian females: the unusually long, sub-fecund, reproductive transitions bookending their reproductive lifespans: a) menarche to first birth and b) peri-menopause to menopause. These transitions exhibit marked within- and among-population variation in the timing of their onset, duration as well as in fecundability levels. I hypothesize that this variation is the result of complex trade-offs between direct fitness and indirect fitness gains associated with the provision of allomaternal care to close relatives (siblings, nieces and nephews before reproductive maturation; children and grandchildren during menopause). Methods: To achieve my goals I will continue a cohort study of 107 Guatemalan Kakchiquel Mayan mothers and 100 of their daughters that I initiated in 2000. To study reproductive maturation and senescence, in 2019/20, I will monitor age related changes in their reproductive status through anthropometric evaluations, menstrual diaries and quantification of reproductive bio-markers. The role of socio-ecological conditions at the community and individual levels will be evaluated through social, demographic, dietary, and resource availability interviews as well as morbidity and mortality risk data. Individuals' energy status and physiologic stress levels will be monitored through dietary diaries and the quantification of urinary biomarkers. I will integrate this information with data I have collected since 2000 from the same individuals. Impact: The proposed research will yield the most complete prospective dataset to date to investigate how human females adjust their reproductive strategies according to their cumulative socio-ecological environments in a traditional, subsistence, natural-fertility population. My results will also further our understanding of the role that social networks have on female reproductive development and senescence. The knowledge gained regarding human females' trade-offs between direct and indirect fitness during these two rare reproductive transitions should both, yield novel theoretical insights into the selective processes that have shaped human females' reproductive life histories and guide the study of similar phenomena in other cooperatively-breeding species.