Mutationism is a concept in evolutionary biology that refers to the idea that species evolve through sudden and dramatic changes, caused by random mutations. However, this concept has been gradually replaced by more modern ideas that emphasize the role of gradual changes and natural selection in the evolutionary process. Synonyms for mutationism include saltationism, which describes the belief that evolution occurs through sudden leaps, and macromutationism, which refers to the idea that mutations can produce large-scale changes in organisms. Other related concepts include evolutionary saltation, quantum evolution, and hopeful monsters, which all describe the idea of sudden and radical evolutionary changes.