Monday, November 21, 2016

Archaeology and Analysis


Archaeology and Analysis: Intro

The typical steps to studying organic residues are extraction, instrumentation, and interpretation. Extraction is the removal of the residue from the artifact. The removal of residues can be done through a selection of solvent, temperature and pressure. Instrumentation is the process of separating the removed residue into parts. Chromatograph was the main example used in lecture of 3.985, with gas and mass methods being used depending on the sample. Interpretation is the process of identifying and analyzing the residue’s constituent parts.

Ideal and Aged

The ideal situation would be comparable to the finger print database, where the chromatograph can be compared with a large library of known materials to create a reliable identification without much effort. This is the end goal of ARCHEM. However, ancient materials are quite different from the recently collected samples. For interpretation, there is a balance between achieving a perfect match and the reality of material’s degradation. Due to this, the fragmentation pattern is the most useful technique. Additionally, the analysis of these trace amounts is quite advanced, using isotopes and chemical ratios to date. Combined with ARCHEM, the process of extraction, instrumentation, and interpretation are the method for studying organic residues.

Example: Lipids in Pottery

Lipids that have been left in pottery can be compared against modern samples. Lipids are good for analysis because they are fairly stable since they’re C based and are insoluble in water. This means that they stick around, although there is some degrading. Archaeologists can find how domestication has affected human diet by the introduction of milk. The challenge is that fatty acids are not enough to determine the presence of milk. Also, lipids in pottery can mix; it’s not clear the order that the organic commodity was introduced to the pottery. You can read more about the methods of this example here. However lipids remain a useful material to be focused on with tools of analysis of porous materials like pottery.
 Investigations of vessels dating from the Neolithic period show that biomolecular information, i.e. the structures, distributions, and particularly compound specific d 13 C values derived from individual acyl lipids, can be used to distinguish between subcutaneous fats of the most important classes of domesticated animals exploited by ancient man.
-- New Criteria for the Identification of Animal Fats Preserved in Archaeological Pottery, by Evershed, H. R. Mottram, S.N. Dudd, S. Charters, A. W. Stott, G. J. Lawrence (1997)

Conclusion

The broad implication of studying organic commodities is a movement toward a holistic approach to analysis. By layering information gained through different aspects of analysis and the environment, a better understanding of ancient societies can be found.  The study of organic commodities suggests that a holistic approach would be more useful to approaching archaeological sites and their analysis. For the selection of site on to the preservation of ARCHEM samples, a range of disciplines is necessary. The analytical methods must match the goals of the investigation as informed by a historic background of the culture.