Micro-sampling of human bones for mobility studies: diagenetic impacts and potentials for elemental and isotopic research

The nature of long bone formation and the pathways of interaction between bone samples and the burial environment suggest that portions of the bones disconnected from the arterial system are resistant to diagenetic alteration. Preliminary work on femurs from Early Bronze Age hunter-gatherers in Cis-Baikal, Siberia shows that the nature and progression of chemical changes in the bone matrix due to microbial attack can be analyzed using laser ablation inductively coupled plasma mass spectrometry. Intra-osteon variability in elemental concentrations and strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) indicate the presence of unaltered portions of bone within diagenetically modified bone and suggest that useful data remain accessible. These biogenic signals can potentially be useful for mobility research in broad terms and the smaller timescales within an individual's lifetime (months, years), accessible therein. Laser ablation micro-sampling of femur specimens showed that intra-osteon elemental composition of Ba, Re, and Cs varied within and was correlated between multiple osteons of a single bone. Portions of chemically unaffected bone were identified within, and effectively discriminated from diagenetically altered bone tissue. Areas showing visual alterations and erratic or uncorrelated Ca and Sr elemental results also had anomalous Sr isotope ratios, suggesting diagenetic alteration in those places. Compositional and isotopic analysis of intact portions of bone supports the hypothesis that hunter-gatherer groups in Cis-Baikal made numerous major movements during their lives. Microscopic analysis of long bones clarifies aspects of biodeterioration and correlations between trace elemental results and diagenetic alteration. Micro-sampling of intact portions of bone expands the scope of available materials for research on mobility and other aspects of human past behavior.