Historical overview and new directions in bioarchaeological trace element analysis: a review

Abstract

Given their strong affinity for the skeleton, trace elements are often stored in bones and teeth long term. Diet, geography, health, disease, social status, activity, and occupation are some factors which may cause differential exposure to, and uptake of, trace elements, theoretically introducing variability in their concentrations and/or ratios in the skeleton. Trace element analysis of bioarchaeological remains has the potential, therefore, to provide rich insights into past human lifeways. This review provides a historical overview of bioarchaeological trace element analysis and comments on the current state of the discipline by highlighting approaches with growing momentum. Popularity for the discipline surged following preliminary studies in the 1960s to 1970s that demonstrated the utility of strontium (Sr) as a dietary indicator. During the 1980s, Sr/Ca ratio and multi-element studies were commonplace in bioarchaeology, linking trace elements with dietary phenomena. Interest in using trace elements for bioarchaeological inferences waned following a period of critiques in the late 1980s to 1990s that argued the discipline failed to account for diagenesis, simplified complex element uptake and regulation processes, and used several unsuitable elements for palaeodietary reconstruction (e.g. those under homeostatic regulation, those without a strong affinity for the skeleton). In the twenty-first century, trace element analyses have been primarily restricted to Sr and lead (Pb) isotope analysis and the study of toxic trace elements, though small pockets of bioarchaeology have continued to analyse multiple elements. Techniques such as micro-sampling, element mapping, and non-traditional stable isotope analysis have provided novel insights which hold the promise of helping to overcome limitations faced by the discipline.

Supplementary information: The online version contains supplementary material available at 10.1007/s12520-020-01262-4.

Keywords: Bioarchaeology; Diagenesis; Element mapping; Micro-sampling; Non-traditional stable isotope analysis; Trace element analysis.

Fig. 1

Review of recent (2000–2019) literature (n = 139) using ⁸⁷Sr/8⁶Sr isotopes to analyse provenance, by year. Articles were systematically compiled from six relevant and impactful journals (Journal of Archaeological Science [n = 55], Archaeometry [n = 12], American Journal of Physical Anthropology [n = 26], International Journal of Osteoarchaeology [n = 13], Archaeological and Anthropological Sciences [n = 20], Journal of Archaeological Science: Reports [n = 13])

Fig. 2

a, b SR-XFI elemental map of Pb from cortical bone samples from two British Royal Navy personnel from colonial Antigua. The intensity of Pb varies in accordance with bone microarchitecture, wherein cement lines (CL) and central canals (CC) of osteons are enriched. Interstitial fragments (IF) of former osteons and primary lamellae are similarly enriched. Resorption spaces (RS) represent active regions of bone remodelling. This naval population experienced high levels of sustained Pb exposure (reproduced and modified from Swanston et al. , PLoS One, under Creative Commons Attribution (CC BY) license)

Fig. 3

Within the brown bear (Ursus arctos) canine tooth root pictured in (a), element distribution maps of Zn (b), Zn/Ca ratios (c), and Sr/Zn ratios (d) were compiled using LA-ICP-MS. Zn, Sr, and Ca distributions in dental increments were used to infer seasonal migration, feeding, and hibernation patterns (originally published in Galinová et al. and reproduced with permission from Talanta)