UC Davis

When people experience food stress or a lack of consistent access to nutritional resources during their life, these stresses often leave osteological markers on the skeleton. During such periods, synthetic processes are compromised and nutrients are often scavenged from other parts of the body, such as bones, to balance competing biological demands. After death, various taphonomic processes will result in decomposition of the body and degradation of the skeletal remains, which eliminate many indicators of starvation and/or markers of physiological stress. However, some of these processes leave osteological signatures that can be detected over archaeological or forensic time frames, particularly in tooth enamel because it is the most robust human tissue. This study, therefore, hypothesizes that the enamel proteome preserves markers of biological stress. Skeletal pathologies noted on ancestral Ohlone skeletal remains from a Late Period (ca. AD 13001700) site in Central California were used to select individuals identified as biologically stressed and compared to individuals with no visible pathologies using Label-Free Quantitative Proteomics. Protein trends correlated with phenotypic expression of biological stress provide more context to the biological processes behind the osteological expressions of those stressors. We demonstrate that biological stress related to starvation resulted in a relative decrease in mineralization proteins, a relative increase in enamel collagen, and changes in the non-specific and targeted immune system. Further, there was no sex-linked bias in biologically stressed individuals that would account for these physiological changes; males and females experienced them equally. This research demonstrates that the enamel proteome preserves a signal of biological stress in archaeological samples, which adds to our anthropological understanding of the lives of people in the past. This method could also be used to identify biological stress in more recent forensic samples.