Trace element distribution in human cortical bone microstructure: the potential for unravelling diet and social status in archaeological bones

Kaare Lund Rasmussen,Marielva Torino,Jørgen Lange Thomsen,Jesper Lier Boldsen,Thomas Delbey,Lilian Skytte,George R Milner,Niels Lynnerup,Simone Schiavone,Lars Agersnap Larsen

doi:10.1186/s40494-020-00457-1

Abstract

Variation in the trace element chemistry of cortical bone microstructure is delineated for interred and non-interred human femora. This was done to investigate the range of element concentrations that might occur within single bones, specifically the original laminar bone and later osteons, and its potential for investigating chemical life histories. To do so, femora were chosen from individuals who experienced quite different ways of life over the past two millennia. The distributions of Sr, Ba, Cu, and Pb, mostly in partial (early) and complete (late) osteons, in cross-sections of proximal femora were characterized through Laser Ablation Inductively Coupled Plasma Mass Spectrometry. Absolute calibrations of these data were obtained using solution Inductively Coupled Plasma Mass Spectrometry on adjacent dissolved bulk samples. Chemical life histories were approximated by classifying bone microstructure into four categories: laminar bone and 1st, 2nd, and 3rd generation osteons. This four-part sequence, on average, charts the temporal dimension of an individual’s life. Consistent with recent studies of medieval bones, Sr and Ba are thought to be mainly responsive to diet, presumably related to the consumption of mostly locally produced food, while Cu and Pb do the same for heavy metal exposure often attributable to social status or occupation. No systematic differences in these elements were found between interred and non-interred individuals. The effect of diagenesis on interpretations of life histories based on archaeological bone, therefore, are minimized by plotting element concentrations across cortical bone cross-sections.

Highlights

This study builds on earlier work that involved the elemental mapping of microscopic features visible in cortical bone cross-sections to identify signals attributable to diagenesis, as opposed to those reflecting life experiences, notably dietary composition and residential location [1]
In addition to what can be said about the lives of past people, this approach contributes to an understanding of the range of variation that occurs in the elemental composition of the inorganic fraction of bone in single individuals
Cortical bone cross-sections from two femora that had never been buried—one dating to the eighteenth or nineteenth centuries, and another ca. 2000 years old—were subjected to LA-Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analyses, as were four femora excavated from Danish medieval to post-medieval cemeteries

Summary

Introduction

This study builds on earlier work that involved the elemental mapping of microscopic features visible in cortical bone cross-sections to identify signals attributable to diagenesis, as opposed to those reflecting life experiences, notably dietary composition and residential location [1]. These results parallel those of Swanston et al [2, 3] and Choudhury et al [4] who characterized the distributions of Sr and Pb by means of synchrotron radiation in long bone cross sections from archaeological skeletons that were about two centuries old, and the work of Pemmer et al [5] and Wittig et al [6] who examined microstructural variation in trace element concentrations in modern bones. By far the most common way of characterizing bone composition, combine many such structures, so they track neither the variation present in single individuals nor changes that take place during a lifetime

Results

Discussion

Conclusion