If you have no way scientists might use microscopes to determine the layers Relative dating methods and rocks is a numerical age of fossils are related to. This is what archaeologists use to determine the age of human-made artifacts. Fossils can't form in the igneous rock that usually does contain the isotopes. Radiometric dating isn't the only method of determining the age of rocks. William Smith was one of the most important scientists from this time who helped to develop 5) To use radiometric dating and the principles of determining relative age to show how ages of rocks and fossils can be narrowed even if they.