This chapter details a comparative genetic analysis of several candidate genes associated with acellular cementum, namely ALPL, BMP-2, BMP-7, and ARNTL. More than 40 species of mammals, reptiles, and birds were included in this analysis. For each gene, we investigated the type of selection that best characterized its evolutionary history, identified species in which these genes were recently subject to positive selection, and demonstrated specific behavioral and morphological characteristics that influence the selection pressure on these genes. We found that, overall, ALPL, BMP-2, BMP-7, and ARNTL have been subject to purifying selection in the examined taxa; however, recent positive selection on three of these genes was identified in species that have experienced recent, rapid evolutionary changes in dental anatomy. In addition, we found that several species-specific characteristics, including diet, lifespan, tooth count, and radicularity, significantly predicted lineage-specific selection pressure on these genes. This chapter demonstrates that cementum genes have undergone significant evolutionary changes, and that certain phenotypic characteristics have influenced such changes

In modern humans, counts of tooth cementum annulations (TCA) have been widely used to determine adult age at death using classical histology. This destructive technique requires physically thin sectioning the teeth which may not be an option for valuable fossil and subfossil specimens. For over a decade, propagation phase contrast synchrotron X-ray microtomography (SRμCT) at the European Synchrotron Radiation Facility has paved the way to non-destructively visualize dental microstructures that remain otherwise invisible to conventional X-ray absorption-based μCT. Here we extend the use of SRμCT to the non-destructive visualization of TCAs in known age archeological modern human teeth, for adult age at death estimation. Our results show that virtual sections are able to elucidate true cementum annulations even if their visibility is often close to the resolution limit of our setup. This is a promising first step in non-destructive adult age at death estimation which future technical fine-tuning will undoubtedly improve further