Which best describes the process of carbon-14 dating? Carbon-14 decays at a constant rate, and scientists measure the amount of carbon in a fossil to determine its age. Scientists use a biological compound found in all living things to track Carbon-14 over time. Scientists compare the Carbon-14 levels in present humans with human fossils. Scientists find Carbon-14 in the rugged desert of Ethopia and implant it into fossils, which then show a constant rate of decay.