Evolutionary theory says all life derived from previous life forms and differences between one plant and animal species to another results from genetic and physical modifications in successive generations.
The evolutionary view has long been in existence. The Greeks believed in a form of evolution. In the 18th and 19th centuries, European scientists and philosophers --particularly the French -- put forth formal theories.
Today, the scientific community largely believes evolution is fact. What troubles some Christians, especially fundamentalists who regard the Bible as God's literal word, is that "godless" evolution runs counters to the doctrine of divine creation.
Creationism grew as an antithesis to the evolutionary movement. Its proponents say creationism is valid science that exposes the weaknesses and fallacies of evolutionary theory.