Methodological strategies to assess the degree of bone preservation for ancient DNA studies

Background: Archaeological bones contain only small amounts of DNA due to post-mortem DNA degradation and the changes endogenous DNA is subjected to during diagenesis. An important step before undertaking such time-consuming and costly analyses as ancient DNA investigation is to predict the presence of DNA in ancient samples. To date, the leading screening method has been amino acid racemization; however, other analytical techniques can also be used to assess the degree of bone preservation. Aim: The aim of the present study was to relate the presence of DNA with bone preservation in order to select samples potentially suitable for ancient DNA analysis. Subjects and methods: Bones collected from several archaeological sites, different locations (cave, rockshelter or sub divo) and diachronic periods were selected for analytical and spectroscopic analysis in order to correlate bone tissue preservation with the presence of DNA. Different techniques were combined to assess the degree of preservation of organic and inorganic components. Results: As determined by different analytical methods, preservation of the inorganic component was best associated with the presence of DNA. Conclusion: Evaluation of the bone preservation state may be an efficient step to predict the presence of DNA in ancient samples prior to aDNA analysis.