Bone diagenesis in a Mycenaean secondary burial (Kastrouli, Greece)

Abstract

This paper presents the characteristics of bone diagenesis in a secondary commingled Mycenaean burial in Kastrouli (Phocis, Greece) through the histological (light microscopy), physical (FTIR-ATR), and biochemical (collagen) analysis of seventeen human (including two petrous bones) and seven animal bones. Post-mortem modifications in bone microstructure, bioapatite, and collagen were characteristic of burial environments with seasonal groundwater and temperature fluctuations. The two human petrous bones displayed a lack of microscopic focal destruction (MFD) sites and a generally good histological preservation, but although a small sample size, did not show any better bioapatite and collagen preservation compared with human femora. Intra-site variations were defined by three main diagenetic patterns that display differences in histological modifications, crystallinity changes, and collagen degradation. These different patterns were either related to different microenvironment conditions and/or influenced by possible differences in the early taphonomic histories experienced by bones prior to secondary deposition. Further, this study highlights the importance of infrared splitting factor (IRSF), carbonate/phosphate ratio (C/P), and general histological index (GHI) for the qualitative assessment of archaeological bone, and the potential use of amide/phosphate ratio (Am/P) as a collagen predictor.

Diagenetic processes in Quaternary fossil bones from tropical limestone caves

“…Diagenesis promotes the loss of B-type carbonate 13,38 . For this reason, the rates of PO 4 3− and B-Type CO 3 2− are used to evaluate the diagenesis process in fossil bones 6,18,[66][67][68] . In Raman scattering, only the B-type carbonate band is present 26,69 and appears at 1070 cm −1 .…”

Screening archaeological bone for palaeogenetic and palaeoproteomic studies

“…Collagen was extracted from 226 samples (including 62 petrous bones; see S1 Table) using a modified Longin [66] method as in Kontopoulos et al [49]. The exterior surfaces of bone samples were mechanically cleaned using a scalpel.…”

“…The relative phosphate content (exogenous phosphate uptake) can also lead to poor agreement of collagen estimates with collagen yields [49,59]. It can be argued that improving the accuracy of the amide I component requires its decoupling from the phosphate signal [49]. However, the use of the peak height at 1640 cm -1 after baseline correction (see 2.2.)…”

“…The IRSF reflects the relative changes in average BAp crystal size and homogeneity, while the carbonate-to-phosphate ratio reflects the relative changes in the carbonate environment of BAp (i.e. carbonate loss, carbonate uptake via adsorption to crystal surfaces or substitution in the crystal lattice, and phosphate-carbonate exchange [49]). However, although FTIR spectroscopy is often proposed as a potential screening tool for endogenous DNA [39,40,45,50] in archaeological bone due to its minimally-destructive, time-and cost-efficient nature, the prediction of the endogenous DNA survival has been deemed extremely difficult and it has never been linked to the amount of endogenous DNA preserved in bone [39,45].…”

“…fragmentation of the polypeptide chains [35,[54][55][56][57] reflected in changes in IRSF and C/P), often show no strong correlation with collagen wt. % [49]. The Am/P ratio (amide-to-phosphate; 1640 cm -1 / 1010 cm -1 ) has been extensively used for the assessment of the organic content in bone [58,59], as the amide I peak at c. 1640 cm -1 is considered characteristic of proteins and peptides [60,61].…”