The preservation of buried bone varies with soil type. Bones from acidic soil areas, such as Mesoamerica, will be softened and often in poor condition. Careful excavation of skeletons, with complete clearing of the soil, is essential. Most bones can be cleaned with warm water. Skulls should be examined first for remnants of brain tissue and for ear ossicles.
Hot paraffin wax, formerly used for conservation of bone, can be damaging. Shellac preserves the surface but tends to peel off in a few years, taking bone with it. Soluble plastics are the best preservatives. Plaster of Paris is good for support but difficult to remove from bones (Brothwell, 1972).
Examination of mummified remains depends on rehydration of the tissues. Ruffer's rehydrating solution, still in use today, is 50 parts water, 30 parts absolute alcohol, and 20 parts 5% sodium carbonate solution, most easily prepared by dissolving 0.6 gm of sodium carbonate in 42 ml of water and adding 18 ml of absolute (100%) alcohol. Allison simplified Ruffer's technique by immersing the tissue in Ruffer's solution until fully rehydrated to visual inspection (usually 24-48 hr). The tissue is then fixed in alcohol and processed. If the tissues dissolve in the solution it is because they are completely contaminated by bacteria. The solution always develops a dark brown turbidity (Zimmerman & Kelley, 1982).
A variety of special stains can be used to demonstrate specific features of the tissues. In general, connective tissues and any foreign elements, such as pigments, bacteria, or parasites are best preserved, while epithelial tissues fare less well. Thus the connective tissues stains are those used most. The standard hematoxylin and eosin is useful only in a very general sense. Other techniques that have been applied to rehydrated tissue include plastic embedding of bone specimens and scanning and transmission electron microscopy.
Dating of biological materials, human or nonhuman, is often of importance in dating an archeological site, either independently or in correlation with conventional archeological techniques such as the evaluation of pottery, hieroglyphic texts or other artifacts, or historical records. In paleopathology, dating is essential in providing an historical context for the evaluation of disease processes detected. Radiocarbon dating is the "gold standard," but a variety of other techniques are applicable. These include amino acid racemization, which is temperature dependent, electron spin resonance, and ancillary techniques such as dendrochronology, mummification styles, and tattoos (Zimmerman & Angel, 1986).
Age determination is another important facet of the study of human remains, allowing the construction of population profiles and the development of a paleoepi-demiologic approach. At the individual level, many diseases occur in specific age ranges and age determination can be a critical factor in differential diagnosis, particularly with regard to bone diseases. In contrast to dating, no single aging technique is best. Techniques used include gross evaluation of the skeleton and viscera, hand-wrist radiographs, bone histology, dental changes, and, in special cases, amino acid racemization (Zimmerman & Angel, 1986).
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