THE STUDY OF MOLECULAR MARKERS OF HUMAN ACTIVITY - THE USE OF COPROSTANOL IN THE SOIL AS AN INDICATOR OF HUMAN FECAL MATERIAL

Coprostanol (5beta-cholestan-3beta-ol) is a metabolic product of chole sterol, formed by microbial action in the mammalian gut (the usual pro duct of cholesterol reduction outside the gut, in mammalian tissues an d sediments, is 5alpha-cholestan-3beta-ol). Coprostanol is the major s terol in human faeces, and has been routinely studied as a marker of ( modern) sewage pollution in marine and lacustrine sediments. This has led to the search for coprostanol in archaeological soils, in order to detect the presence of faecal material. Solvent extraction of the soi l total lipids was followed by fractionation using thin layer chromato graphy, to isolate the steroids present in the soil. These were then a nalysed by combined gas chromatography/mass spectrometry (GC/MS), usin g selected ion monitoring (SIM) to detect and quantify specific compou nds. Samples from a range of sources were analysed, including modern l atrine deposits, a 17th-century garderobe, a mediaeval garderobe and t wo suspected Roman cess-pits. Coprostanol and its homologues were dete cted not only in the modern and aged cess samples, but also in the con trol samples, suggesting its ubiquitous occurrence in the environment, albeit at a low concentration. However, by measuring the relative abu ndances and ratios of the 5beta-stanols, a chemical signature distinct ive of faecal material could be established, independent of the simple occurrence of coprostanol in the soil. It was shown that coprostanol, and its homologues produced by the same microbial mechanism in the gu t, were reliable markers of the presence of faeces in soils when found in the appropriate relative abundances. A method of analysing very sm all quantities of specific molecular marker compounds preserved in soi ls has thus been applied to archaeological materials, enabling a parti cular organic residue to be identified where conventional physical met hods of analysis might not be successful.