Analytical Methods:Biomolecules
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Contents |
[edit] Biomolecules
| Scale | A specialist laboratory technique |
| Questions | Identification of manure inputs to soil; study of ancient diet and agriculture. |
| Samples and storage | Specialist advice should be sought prior to sampling. |
| Time and Cost | This specialist technique is costly hence specialist advice should be sought early on to ascertain the potential for further analysis to answer specific questions. |
| General comments |
The term 'biomolecules' is often used to refer to specific biomarkers of faecal and other organic materials. Coprostanol is formed by the microbial breakdown of cholesterol in the gut of higher mammals. Hence, coprostanol is a specific biomarker for faecal matter. Animals consume compounds called stenols from the plants they consume. These too are broken down in the gut into a new series of compounds known as 5ß-stanols (Bull et al. 1999). Other biomarkers that have been applied to archaeological materials include wax esters, alkanols and n-alkanoic acids that have been used to identify turf inputs (Simpson et al. 1998).
[edit] Questions
Biomolecules have been used to identify manuring in archaeological soils, whilst the relative proportion of different 5ß-stanols provides information about diet and may help identify the animal that is the source of the faecal material. Comparison of other biomarkers such as alkanols and n-alkanoic acids between archaeological and reference soils may also help to identify other manure inputs such as turf. Biomolecules have also been used to study the abandonment of a wastewater course in Athens (Bull et al 2003) and the identification of middens and less successfully animal pens at Çatalhöyük (Bull et al. 2005).
Examples of situations where biomolecules have been successfully used include:
[edit] Samples and storage
Specialist advice should be sought before sampling to ascertain the potential for preservation of biomarker compounds and to identify suitable sample sizes and sampling strategy. Samples should be kept refrigerated and analysed as soon as possible after sampling. Control and reference samples are important for the subsequent interpretation of results.
[edit] Analysis
Analysis is a specialist procedure that involves the use of solvent extraction and gas chromatography to isolate organic compounds and mass spectrometry to identify them.
[edit] Data and interpretation
Confident interpretation of organic data requires a good knowledge of the origin and formation of different compounds and the likely taphanomic effects of burial. Organic molecules are susceptible to further decay in the soil, which can limit their sensitivity and usefulness. Identification of specific inputs ot soils where a mixture of manure materials have been added. Interpretation of signatures requires specialist knowledge, but the involvement of the archaeologist in this process is important to ensure that the history of the site is fully understood and considered.
[edit] References
- Bull, I.D., Elhmmali, M.M., Perret, P., Matthews, W., Roberts, D.J., and Evershed, R.P. (2005) Biomarker evidence of faecal deposition in archaeological sediments at çatalhöyük. In, Inhabiting Çatalhöyük. Reports from the 1995-1999 seasons (Ed. I. Hodder) McDonald Institute Monographs, McDonald Institute for Archaeological Research, University of Cambridge, Cambridge, UK and the British Institute of Archaeology at Ankara, c/o British Academy, London, UK, 415-420.
- Bull, I.D., Elhmmali, M.M., Roberts, D.J., and Evershed, R.P. (2003) Using steroidal biomarkers to track the abandonement of a Roman wastewater course at the Agora (Athens, Greece). Archaeometry, 45, 149-161.
- Bull, I.D., Simpson, I.A., van Bergen, P.F., and Evershed, R.P. (1999) Muck 'n' molecules: organic geochemical methods for detecting ancient manuring. Antiquity, 73, 86-96.
- Simpson, I.A., Dockrill, S.J., Bull, I.D., Evershed, R.P. (1998) Early anthropogenic soil formation at Tofts Ness, Sanday, Orkney. Journal of Archaeological Science, 25, 729-746.
[edit] External links
