Doctoral Dissertation Improvement: Effects of Stress on Onset of Middle Childhood among Aka Foragers and Ngandu Horticulturalists

目前的理论认为，人类的童年是一个评估阶段，儿童利用他们对风险或不可预测性的经验（例如，压力源）来塑造未来的生活史策略。这表明，发育转变的时间可能取决于前一阶段的经验。博士生Courtney Helfrecht（华盛顿州立大学）在Courtney Meehan博士的指导下，在中非共和国（CAR）的Aka觅食者和Ngandu园艺家中测试了早期压力经历对儿童中期发病年龄及其生物学相关性（肾上腺素初长）的影响。初步数据表明，童年中期是一个文化定义的阶段，与认知和社会能力的变化有关。本研究在此基础上增加了三个目标：1）评估文化和环境压力; 2）确定儿童中期和肾上腺初发的实际发病年龄; 3）评估哪些压力因素影响儿童中期和肾上腺初发的发病时间。这项综合性研究是第一个使用观察，激素，访谈，人口统计和跨文化数据来实证研究这种关系的研究。通过华盛顿州立大学和乔治华盛顿大学之间的合作，使用头发激素分析，初步收集的头发样本提供了肾上腺初发时间的人群概况。第二个收集允许跟踪生物发育和重复测量经历的压力（皮质醇）。通过研究压力，生物学和文化之间的相互作用，我们走向了解与发育可塑性和生活史事件的时间相关的因素，以及它们对人类童年进化的贡献。这项研究的结果将是有价值的多个领域，包括生物文化人类学，儿童发展和认知心理学。这将进一步增加两个小规模社会的儿童人种学数据，并促进与班吉大学的持续合作。 这笔赠款将有助于促进有前途的研究生的科学培训。

Current theory proposes that human childhood is an assessment phase where children use their experience with risk or unpredictability (e.g., stressors) to shape future life history strategies. This suggests that timing of developmental transitions may depend on experience in the preceding phase. Doctoral student Courtney Helfrecht (Washington State University), under the guidance of Dr. Courtney Meehan, tests the hypothesis that early experience of stress has significant effects on age of onset for middle childhood and its biological correlate (adrenarche) among Aka foragers and Ngandu horticulturalists of the Central African Republic (CAR). Initial data indicate that middle childhood is a culturally-defined phase associated with changes in cognitive and social abilities. This research builds from that with three additional goals: 1) assessment of cultural and environmental stressors; 2) determination of chronological age of onset for middle childhood and adrenarche; and 3) evaluation of which stressors affect timing of onset for both middle childhood and adrenarche. This integrative study is among the first to empirically examine this relationship using observational, hormonal, interview, demographic, and cross-cultural data. An initial collection of hair samples provides population profiles for timing of adrenarche using hair hormone analysis, conducted via collaboration between Washington State University and The George Washington University. A second collection allows tracking of biological development and a repeated measure of experienced stress (cortisol). By investigating the interaction between stress, biology, and culture, we move toward understanding the factors associated with developmental plasticity and the timing of life history events, as well as their contributions to the evolution of human childhood. The results of this study will be valuable to multiple fields, including biocultural anthropology, child development, and cognitive psychology. It will further add to ethnographic data on childhood among two small-scale societies and foster continued collaboration with the University of Bangui. This grant will help to advance the scientific training of a promising graduate student.