What Doesn't Kill You Makes You Stronger? Examining Relationships Between Early-Life Stress, Later-Life Inflammation and Mortality Risk in Skeletal Remains

Objectives

This paper explores conflicting perspectives on the adaptive significance of phenotypic plasticity during fetal and early postnatal development and the impact that stressors experienced during this critical early-life period have on later-life morbidity and mortality risk.

Methods

The sample (n = 216) comprised archeologically-recovered human skeletons. A geometric morphometric (GM) method was employed to evaluate first permanent molar (M1) fluctuating asymmetry (FA) and provide a proxy for early-life stress. Shifts in later-life physiology were inferred through two inflammatory lesions: periosteal new bone formation (PNBF) and periodontal disease (PD). To explore mortality risk, age-at-death was estimated through dental development for skeletally immature individuals (n = 104) and through senescent skeletal changes for mature skeletons (n = 112).

Results

Significant differences were found in M1 FA between groups, with the immature cohort associated with elevated FA. Within-group analysis revealed age-at-death in the immature group had a significant positive relationship with M1 FA and PD presence. In the mature group, alongside sex and the co-occurrence of PD and PNBF, FA was a significant predictor of a shorter life. Higher FA was also associated with active and bilaterally expressed PNBF.

Conclusions

It is theorized that early-life stress, if survived, programmed a hyperinflammatory response to environmentally-mediated physiological perturbations which increased the chances of survival during subsequent development but also elevated later-life mortality risk. Findings demonstrate a complicated relationship between developmental stress and physiological shifts that helps to illustrate the adaptive significance of early-life programming and support the Thrifty Phenotype hypothesis.