Fossils Evidence of EvolutionSince its formation 4.5 billion years ago, the earth itself has changed continuously. This slow change is known as geologic evolution. Many species also have changed since they first appeared on the earth. This process is known as organic evolution.The study of fossils provides strong evidence of organic evolution. A fossil is any trace or remains of an organism that has been preserved through natural processes. Special circumstances are required for a fossil to form. In the majority of fossils, the soft tissues have decayed and only the hard parts, such as bones or shells have been preserved. In some fossils, however, an entire organism has been preserved.Figure 1Calculating the Age of FossilsThere are two types of fossil dating. Any method that determines the order in which events occurred is called