To establish the age of a rock or a fossil, researchers use some type of clock to determine the date it was formed. Geologists commonly use radiometric dating methods, based on the natural radioactive decay of certain elements such as potassium and carbon, as reliable clocks to date ancient events.

How far back do fossils date?

Scientists called geochronologists are experts in dating rocks and fossils, and can often date fossils younger than around 50,000 years old using radiocarbon dating. This method has been used to provide dates for all kinds of interesting material like cave rock art and fossilized poop.