شیمی تجزیه در تحقیقات باستان شناسی Analytical Chemistry in Archaeological Research

The lay conception of archaeology is often one of treasure hunting, the discovery of rare and fantastic exotica, and the collection of fine works of ancient art, the “Indiana Jones” paradigm, partly because of the famous discoveries of Heinrich Schliemann (who excavated the Hellenic city of Troy in the 1870s), Hiram Bingham (who rediscovered the Inka sanctuary of Machu Picchu in 1911), and Howard Carter (who explored the tomb of the Egyptian Pharaoh Tutankhamun in the 1920s). Instead, the best of modern archaeology couches itself as carefully designed, empirical, and data-driven research focused on uncovering the human behaviors and social processes behind the artifact. Today’s archaeology is not about finding things; it is about finding things out. The application of analytical chemistry to archaeological materials has become an essential part of modern archaeological investigation. One of the pioneers in using analytical chemistry to study archaeological objects was Alfred Lucas (1867−۱۹۴۵). An analytical chemist with a background in forensic science, Lucas moved to Cairo in 1898 where he worked for various departments of the British Colonial Service. At the age of 55 he retired from the civil service to pursue his interest in Egyptian archaeology.8 Shortly thereafter, Lucas became a consulting chemist for the Egyptian Department of Antiquities (a position he held until his death) and was asked by Howard Carter to assist in the examination and preservation of the artifacts from the tomb of Tutankhamun (Figure 1). He remains best known for his book Ancient Egyptian Materials and Industries of which many editions have appeared since it was first published in 1926. Human beings, like all organisms, modify the chemical constitution of themselves and their surrounding environments as they go about daily activities. These range from the quotidian (procuring, preparing, and enjoying food and beverage; discarding waste; production and use of basic tools) to the culturally specific (use of pigments and dyes for decorative purposes; consumption of stimulants and hallucinogens in ritual contexts; embalming and other treatment of the dead) to the seemingly extraordinary (cannibalism; complex metallurgy; genetic modification of plant and animal populations; applying remedies, treatments, and medicines). All of these behaviors provide fundamental information on how human groups organize themselves politically and economically, how cultural norms regulate responses to social and environmental stimuli, how individuals balance their interests against that of a larger group, and beyond the functional necessities of everyday life, how people choose to render their lives meaningful in a complex and often uncertain world. Analytical chemistry contributes techniques vital for obtaining absolute calendar dates for archaeological sites (radiocarbon and other forms of isotopic dating), linking the raw materials used in prehistory to their geochemical sources (analyses of oxygen, nitrogen, strontium, and other stable isotopes), deducing the elemental composition of artifacts via spectroscopic and elemental fingerprinting (X-ray florescence (XRF), X-ray diffraction (XRD), and neutron activation (NA) analyses), identifying relatively small organic molecules including fatty acids, lipids, sterols, terpenoids, alkaloids, and carbohydrates (combined gas chromatography/mass spectrometry (GC/MS), combined liquid chromatography/mass spectrometry (LC/MS), and combined liquid chromatography/ tandem mass spectrometry (LC/MS/MS)) and for identifying larger organic molecules including peptides, proteins, and nucleic acids (radioimmunoassay (RIA), enzyme-linked immunosorbent assay (ELISA), LC/MS, and LC/MS/MS). In their application to varying types of archaeological materials, each methodological technique holds inherent advantages and disadvantages depending on the nature of the sample and the specific type of human activities in question. Given that budgets are often limited and that the legal and political hurdles to exporting archaeological samples across international borders are often substantial, analytical techniques must be carefully selected to overcome these pragmatic concerns while at the same time optimizing the collection of meaningful data. Analysis now often takes advantage of the wide range of available methods to fully interrogate a sample. Here we loosely organize the extant literature by technique but emphasize that much work involves the application of multiple techniques for assembling complementary and intersecting data sets.