Contaminated carbon dating
Current protocols for ancient DNA and radiocarbon analysis of ancient bones and teeth call for multiple destructive samplings of a given specimen, thereby increasing the extent of undesirable damage to precious archaeological material.Here we present a method that makes it possible to obtain both ancient DNA sequences and radiocarbon dates from the same sample material.
More specifically, we tested three reagents that might enable the recovery of DNA without degrading the organic component of the bone/tooth matrix.Therefore, the biomolecules required for radiocarbon dating and ancient DNA analysis are presumably located in different fractions of the bone matrix, suggesting that it might be feasible to retrieve both from a single sample by targeting the inorganic and organic components of the bone/tooth matrix separately.Such a combined method for DNA and collagen extraction would not only reduce the number of samplings and thereby the amount of material required to perform both techniques, but also substantially increase the amount of material available for genetic analyses.By comparing the number of endogenous DNA fragments recovered during initial DNA release to those obtained from subsequent full lysis of the same bone powder aliquots, we estimate that EDTA released 42% and 99% of the endogenous DNA from samples A and B, respectively, while acidic phosphate released 53% and 50% (Fig. In contrast, no more than 20% of the endogenous DNA was released by incubation in the neutral phosphate buffer from either sample. While the size distributions of DNA fragments retrieved from EDTA and neutral phosphate were similar, acidic phosphate showed an enrichment for short DNA molecules (Supplementary Fig. Prompted by these results we performed binding experiments of DNA to hydroxyapatite and bone powder, and found that when compared to long molecules, short molecules are both more efficiently released from hydroxyapatite by acidic phosphate and more efficiently retained from acidic buffers during subsequent silica-based DNA purification (Supplementary Figs S2 and S3).DNA recovered from this buffer also showed a severe decrease in the relative abundance of endogenous vs. Comparing the suitability of EDTA, neutral and acidic phosphate treatments for DNA release prior to collagen extraction and radiocarbon dating.