Introduction To Evolution What is Evolution? Evolution is the process by which all living things have developed from primitive organisms through changes occurring over billions of years, a process that includes all animals and plants. Exactly how evolution occurs is still a matter of debate, but there are many different theories and that it occurs is a scientific fact. Biologists agree that all living things come through a long history of changes shaped by physical and chemical processes that are still taking place. It is possible that all organisms can be traced back to the origin of Life fro