An investigation into the effects of X-ray on the recovery of ancient DNA from skeletal remains

Abstract

The application of radiographic imaging methods like conventional X-Ray and computed tomography (CT) in bioarchaeological research is normally considered to be non-invasive. While this holds true on the macro- and microscopic level, little is known about potentially induced damage on the molecular level that could inhibit the successful recovery of ancient DNA (aDNA) from such specimens. Although there has been speculation concerning possible damage to DNA recovered from ancient remains following exposure to radiation, little research has been published. Past studies attempted to determine the specific effect of X-ray and computed tomography on the amplification of DNA from bone of recently butchered animals. Although the results suggested exposure to clinical level of radiation decreased the recovery of aDNA, the un-dehydrated state of the samples might have biased the results. In this study we utilized dry human archaeological bones from nine prehistoric and historic individuals and exposed them to different levels of radiation using conventional X-ray to more accurately examine the issue. Employing Next Generation Sequencing (NGS) of shotgun sequencing libraries, quantitative PCR (qPCR), and multiplex PCR of autosomal genetic markers we show that neither the exposure to conventional X-ray dosages (moderate irradiation) used in archaeological imaging studies nor 20-fold increased dosages (strong irradiation) have a significant effect on the quantity and quality of DNA that can be recovered from these ancient specimens. We conclude that the application of radiographic imaging methods in bioarchaeology does not impair the success of subsequent aDNA studies if simple precautions are followed.