Stable isotope evidence (Fe, Cu) suggests that sex, but not aging is recorded in rhesus macaque (Macaca mulatta) bone

Objectives: Here, we examine (1) if the sex-related differences in iron (Fe) and copper (Cu) isotope ratios, represented as δ⁵⁶Fe and δ⁶⁵Cu values, respectively observed in humans exist in bulk occipital bone and incisors of male and female non-human primates, and (2) if the variation of Fe and Cu isotope ratios, known to vary in human blood as a factor of age are similar in non-human primate bone. Materials and Methods: Isotope ratios were measured from the skeletal elements of 20 rhesus macaques (Macaca mulatta) with known life history traits. The metals were purified by column chromatography and their isotope ratios measured by MC-ICP-MS. Data were analyzed using generalized additive models (GAM). Results: When accounting for age and sex independently, we found a significant relationship between δ⁶⁵Cu values and occipital bone, but not in incisors. There were no significant relationships observed between δ⁵⁶Fe values, occipital bone, or incisors. Similarly, there were no significant relationships observed between δ⁵⁶Fe values, δ⁶⁵Cu values, and age. Discussion: We suggest that Cu and Fe isotope ratios have the potential to be useful supplementary tools in future research in biological anthropology, but additional studies are needed to further verify the relationship between sex, age, δ⁶⁵Cu, and δ⁵⁶Fe values in primates.