Effect of X-ray irradiation on ancient DNA in sub-fossil bones - Guidelines for safe X-ray imaging.

Sub-fossilised remains may still contain highly degraded ancient DNA (aDNA) useful for palaeogenetic investigations. Whether X-ray computed [micro-] tomography ([µ]CT) imaging of these fossils may further damage aDNA remains debated. Although the effect of X-ray on DNA in living organisms is well documented, its impact on aDNA molecules is unexplored. Here we investigate the effects of synchrotron X-ray irradiation on aDNA from Pleistocene bones. A clear correlation appears between decreasing aDNA quantities and accumulating X-ray dose-levels above 2000 Gray (Gy). We further find that strong X-ray irradiation reduces the amount of nucleotide misincorporations at the aDNA molecule ends. No representative effect can be detected for doses below 200 Gy. Dosimetry shows that conventional µCT usually does not reach the risky dose level, while classical synchrotron imaging can degrade aDNA significantly. Optimised synchrotron protocols and simple rules introduced here are sufficient to ensure that fossils can be scanned without impairing future aDNA studies.

Dental development pathology in wild artiodactyls: Two prehistoric case studies from France.

In this paper we report two unique cases of dental development anomalies observed on prehistoric faunal material from France. The first is a severely malformed first incisor from a red deer, dated to the 13th-12th millennium BC, which is interpreted as a composite odontoma, a rare pseudo-tumor of odontogenic origin. The second is a Mesolithic (9th-8th millennium BC) wild boar skull presenting an anomalous tooth row including a duplication of the upper left second premolar. Both pathologies are discussed in terms of diagnosis and etiology, and comparable archeological cases are sought. We conclude by stressing that the occurrence of these two developmental anomalies appears to have a strong spontaneous component, and that caution should be exercised when considering such defects in terms of populational significance.