Intact archeological human bones and age at death studied with transmission x‐ray diffraction and small angle x‐ray scattering

Abstract

High‐energy, wide‐angle x‐ray scattering (WAXS, x‐ray diffraction) and small‐angle x‐ray scattering (SAXS) were used to study intact human second metacarpal bones (mc2) from two UK archeological sites. A novel method correcting for irregular mass distribution was applied in these transmission geometry experiments done at beamline 1‐ID of the Advanced Photon Source. The authors asked whether there were age‐at‐death‐related changes in carbonated apatite (cAp) lattice parameters and whether SAXS could detect collagen D‐period peaks in the archeological mc2. For each of the two sites, Ancaster and Wharram Percy in England, six female mc2s were studied; for each site, two were from each of three age‐at‐death cohorts (young, 18–29 years; middle, 30–49 years; old ≥50 years) along with a modern control mc2. The Rietveld method was applied to the WAXS patterns to provide precise lattice parameter values. The cAp lattice parameters did not correlate with age‐at‐death estimated from dental wear. From WAXS and the 00.2 diffraction peak widths, four archeological mc2s possessed coherently scattering domain lengths (crystallite c‐axis sizes) that matched that of the modern mc2; SAXS revealed the same four archeological mc2 had D‐period peak intensities equivalent to that of the modern mc2. The other eight archeological mc2s had significantly larger crystallite sizes (than the modern mc2) and weak or absent D‐period peaks, differences attributed to diagenetic changes. Based on these data, the authors suggest that WAXS 00.2 peak width and SAXS D‐period peak intensity can be used with intact bones to select those likely to retain largely unaltered tissue nanostructure, which might be required for other analyses. Taken as a whole, the results suggest detecting age‐related deterioration in nanostructural features may be difficult in bone showing significant bioerosion.

Microcomputed tomography (laboratory and synchrotron) of intact archeological human second metacarpal bones and age at death

“…Synchrotron microCT is required to reveal diagenetic changes in these intact mc2. Observation of microstructure similar to that in the modern (reference) mc2 correlates with X‐ray scattering‐based measures of retained nanostructure (high I D ) and of unchanged c ‐axis crystallite size (Park et al, 2021); the exceptions may reflect variation in diagenesis within a single mc2 and sampling of affected versus unaffected volumes. Only a very small fraction of the collected synchrotron microCT slices were analyzed, and much more could be done with these thousands of slices if one wanted to concentrate on mapping diagenetic changes.…”

“…Before discussing how microCT informs interpretation of the WAXS and SAXS data of Park et al (2021), the authors examine the advantages of microCT characterization of human archeological mc2 compared to other bones. After summary of the WAXS and SAXS data (Park et al, 2021) in Section 4.2, microCT‐based age at death estimation for the mc2 is the subject of Section 4.3. The next subsection explains why the mc2 linear attenuation coefficients were higher than expected for bones, something related to the imaging approach and not to real changes in the bone.…”

“…This study examined the two sets of mc2 from Park et al (2021). The intact archeological and modern mc2 were examined first with laboratory microCT.…”

“…4.2 | Summary of wide angle X-ray scattering and small angle X-ray scattering data (Park et al, 2021) In the related study of the ANC and WP mc2 (Park et al, 2021), In the other eight archeological mc2 (ANC 53, 62, and 168; WP EE99, EE018, WC045, EE22, and NA170), cAp c-axis crystallite size was much larger and D-period peak intensity much lower or nonexistent.…”

“…In the mc2 examined in Park et al (2021), two possibilities exist for the lack of clear differences in lattice parameter with age‐at‐death. First, no lattice parameter differences may have been present at death: The sample size is quite small and there was considerable spread at any given age in the data of Handschin and Stern (1992, 1995).…”