Doctoral Dissertation Research: Life history tradeoffs between testosterone and immune function among forager-horticulturalists

本论文项目将研究能量是如何分配给人类相互竞争的生物需求的。男性生殖努力和免疫功能之间的权衡是几种关于人类生物学进化的理论的基础。研究人员将通过测试个体生理学（包括男性睾酮）如何与寄生虫感染的免疫反应相关，以及生活方式的变化如何影响这种关系来探索这些理论，在寄生虫病负担高的人群中。本研究中确定的感染模式可能有助于通过测量个体生理（激素水平）和生活方式（饮食和住房因素）如何影响寄生虫暴露和传染病风险来告知治疗方案。此外，这些分析将通过教育和感染治疗改善研究地点的个人健康。该项目将支持本科生和研究生在STEM研究方面的培训和指导。该项目评估了Shuar人男性生殖努力和免疫功能之间的预期生活史妥协。生命史理论（LHT）试图解释的时间和上下文敏感的能源分配关键的身体和生殖功能。LHT的一个重要前提是，用于一种功能的资源不能用于另一种功能;因此，可以预测物理和生殖投资的不同方面之间的权衡。这些权衡是生理调节的，包括通过激素水平。例如，激素睾酮（T）被认为是调节生殖努力和免疫力之间的权衡。对非人类动物的研究表明，T通常会增加对与雄性生殖相关的身体特征的投资（例如，肌肉组织），同时抑制免疫功能。然而，这种权衡并没有在人类中得到很好的测试。Shuar经历了相对较高的病原体环境，随后增加了免疫激活成本。此外，病原体暴露情况在其领土上各不相同，并与其获得经济资源的情况有关。这种设置提供了一个很好的机会来测试T档案，免疫和生殖投资之间的假设关系。为了测试这些关联，将收集几种测量方法，包括新鲜粪便样本中每克可观察到的寄生虫物种和卵的存在;唾液样本中的T水平;被认为与发育T水平相关的物理测量。（身高、握力、胸外按压、上臂围和2D：4D手指比）;来自干血点的免疫标记物;以及家庭经济、饮食和生活方式问卷调查数据。此外，这项研究将评估传统生活和城市化的Shuar之间的T曲线是否与病原体暴露的差异有关。因此，这项工作将有助于我们了解人类的生活史，男性生殖和健康，通过记录生殖和免疫反应之间的权衡，两个能量昂贵的功能。

This dissertation project will investigate how energy is allocated to competing biological needs in humans. Tradeoffs between male reproductive effort and immune function underlie several theories about the evolution of human biology. The investigator will explore these theories by testing how individual physiology (including testosterone in men) is associated with immune responses to infection by parasites, and how lifestyle variation influences this relationship, in a population with a high parasitic disease burden. Infection patterns identified in this study may help to inform treatment protocols by measuring how individual physiology (hormone levels) and lifestyle (diet and housing factors) affect parasite exposure and infectious disease risk. Furthermore, these analyses will improve the health of individuals at the study location through education and treatment of infections. The project will support undergraduate and graduate training and mentorship in STEM research. This project evaluates predicted life history compromises between male reproductive effort and immune function among the Shuar. Life history theory (LHT) seeks to explain the timing and context-sensitive allocation of energetic resources to critical physical and reproductive functions. A critical premise of LHT is that resources used for one function cannot be used for another; thus, tradeoffs are predicted among different aspects of physical and reproductive investment. These tradeoffs are physiologically regulated, including via hormone levels. For example, the hormone testosterone (T) is thought to mediate tradeoffs between reproductive effort and immunity. Work with non-human animals has shown T to generally increase investment in physical traits associated with male reproduction (e.g., musculature) while suppressing immune function. However, this tradeoff is not well-tested in humans. The Shuar experience a relatively high pathogen environment, with subsequent increases in immune activation costs. Further, pathogen exposure varies across their territory, and in relation to their access to economic resources. This setting provides an excellent opportunity for testing the hypothesized relations among T profile, immunity, and reproductive investment. To test these associations several measures will be collected, including the presence of observable parasite species and eggs per gram in fresh fecal samples; T levels from saliva samples; physical measures thought to be associated with developmental T levels (height, grip strength, chest compression, upper arm circumference, and 2D:4D digit ratio); immune markers from dried blood spots; and household economic, dietary, and style of life questionnaire data. In addition, this study will assess if T profiles vary between traditionally-living and urbanized Shuar in relation to differences in pathogen exposure. This work will therefore contribute to our understanding of human life history, male reproduction, and health through documenting tradeoffs between reproduction and immune responses, two energetically expensive functions.