Amino acid composition of degraded matrix collagen from archaeological human bone.

In relation to specific burial conditions, the degree of preservation of archaeological bone collagen shows significant variation which cannot be discerned sufficiently by histological inspection. Thus the validity of archaeometric data cannot be confirmed as such and further proof is required. This study deals with diagenetic modifications of extractable collagen from archaeological human bones (14 skeletal series from various locations, inhumation periods and modern skeletal material). The content of proteinogenic and not-proteinogenic amino acids was determined by amino acid analysis compared to experimentally degraded scleroprotein. The resulting amino acid composition of the insoluble extracts differs from native collagen in relation to the specific skeletal series. Five different qualitative categories could be distinguished. Rare and carbon rich amino acids preferably disappeared in the archaeological specimens. Essential and experimentally validated decomposition phenomena as e.g. selective degradation of specific amino acids were confirmed and an example is given for the differentiation of valid from diagenetically altered carbon isotopic signatures by amino acid analysis.

Molecular preservation and isotopy of Mesolithic human finds from the Ofnet cave (Bavaria, Germany).

Favourable burial conditions and self-limiting decomposition processes led to an extraordinarily well molecular preservation of the Mesolithic human skull finds from the Ofnet cave (district Nördlingen, Bavaria). Beyond the extraction of bone collagen, a selection of serum proteins from bone was identified immunologically. Stable carbon and nitrogen isotope ratios from collagen gave clues to dietary behaviour including nursing practices. Diverging results after the application of biochemical protocols (for protein cleaning) and biophysical methods (for stable isotope analysis) are of particular interest: while the first approach failed to quantitatively eliminate anorganic contaminations, the second left some organic, exogenous residues in the samples. Thus, methods for protein extraction must vary according to problem solution and ultimate aim of the study. Taking this into account, application of invasive methods is also encouraged to rare and valuable skeletal finds.