By studying the sedimentary layers in which they are found
By using radioactive dating
By analyzing the genetic makeup of the fossils
By studying the physical characteristics of the fossils
Solution
Scientists use the method of radioactive dating to determine the age of fossils. This method relies on the principle that certain isotopes of elements decay at a known rate over time. By measuring the ratio of isotopes in a sample, scientists can determine how long it has been since the organism died.