This research conducted a two-pronged approach to study the effects of
taphonomic processes by conducting analysis of experimental burials of porcine
femora and parallel analysis of ancient human archaeological remains from
geologically distinct cemeteries. The aim of this study was to identify the major
degradative factors from depositional environments that affect the bone
composition and the retention and retrieval of nucleic DNA from archaeological
bone. Four different experimental burial environments of clay, compost, lime and
sand were designed, displaying different properties of soil type, pH, water content
and organic content. Analysis of the burial mediums and bones were conducted at
regular intervals over an 18 month period. Observations of changes in the burial
medium, comparisons of the rates and degree of soft tissue decomposition, bone
diagenesis from compositional assessment, and bone colour change were made
and analysed in correspondence with the different environments. The analytical
data collected on the diagenesis of the archaeological bone from both studies, was
compared to the DNA profiling success rates.
The research and optimisation of sample preparation and DNA analysis enabled
the most cost-effective and appropriate methods to be identified and utilised in
accordance with the preservation state of the bone samples. This allowed the
analysis of ancient archaeological bone to be analysed in-line with forensic
protocols, to enable a uniform accessible approach to produce comparable results
across different laboratories.
Drawing together the results from the various analytical techniques made it
possible to identify the variables that affect bone diagenesis and the survival of
nuclear DNA, and provide evidence that the rate of decomposition and bone
degradation is affected more significantly by the burial environment than duration
of burial, as stated in the research hypothesis. The presence of water, sand and the
level of organic content were found to be the most degradative variables within the
experimental burial conditions; causing changes in bone crystallinity, and
infiltration of contaminants into the bone. The presence of lime, chalk or limestone in an environment was found to have preserving properties in both the porcine
and human burials, by retarding the rate and degree of soft tissue decomposition,
and reducing the diagenetic changes in bone composition evident from the other
environments.
Despite previous reports of success using analytical techniques as predictive
models for DNA and bone preservation, no correlations with DNA survival could be
established. However the use of a multi-disciplinary approach enabled the
detection and identification of soil contaminants affecting the bone structure and
the ability to amplify DNA, in relation to burial environments. This research
highlighted the importance of utilising multiple analytical techniques, such as
colourimetry, ATR-FTIR, XRF and genetic analysis in order to avoid
misinterpretation and false reporting of the state of bone diagenesis or
preservation and the survival of DNA, due to environmental contaminants within
the hard tissue.
The research confirms the idea that in order to establish optimised sampling and
DNA analysis of archaeological bone, it is imperative that certain protocols are
adhered to. Precautions must be implemented from excavation through to
laboratory analysis to avoid contamination; and correct recording of burial
environment is essential to enable consideration of extrinsic factors and
contaminants when reporting results
