Detection of bone preservation in archaeological and fossil samples

Abstract

Several methods for assessing the preservation of the organic and inorganic components of bone are discussed. Aspects of bone composition (i.e. specific trace element concentrations and stable isotope ratios) provided information on diet and health status in prehistoric and fossil humans. Such information is valuable in understanding the evolution of human adaptation but, prior to the analysis of bone, it is necessary to ensure that the biological signature has not been erased during burial or following excavation. The purpose of the present study was to provide relatively quick methods of scanning sets of bones in order to eliminate ones that are not appropriate for analysis. We present the results of powder X-ray diffractometry and a survey of thin sections of human bones recovered from a coastal site in Georgia (U.S.A.) to assess the preservation of biogenic bone mineral and histological structure. Those bone samples which displayed a lack of histological structure also showed X-ray diffraction patterns which deviated markedly from that of fresh bone. We conclude that a survey of thin sections of a small number of samples in any skeletal population is a rapid, dependable means of eliminating bone which has been altered diagenetically. We also present the results of amino acid analysis of "gelatin" collected using two different methods of extracting the organic component in bone. The "gelatin" which resulted from the demineralization of bone pieces in weak acid (1% HCl) consistently showed a pattern of amino acid composition similar to collagen. Conversely, the "gelatin" which resulted by hydrolyzing demineralized bone powder was unreliable in the retention of protein. Thus, use of the former method, rather than C to N ratios or % yield, appears to be the best means of ensuring analysis of material retaining a biological signature. At this point in time, we can identify bone samples appropriate for trace element and stable isotope analysis even though we cannot always identify the diagenetic process or agent involved.