A review of the fossil and taxonomic evidence for fish evolution is undertaken. No empirical evidence exists for their evolution from non-fish, even though 80% of all known fossils are marine animals, mostly various types of fish. Fully formed fish appeared very "early" in the fossil record, although numerous forms have become extinct. Many fish that are claimed to be multimillions of years old are identical to those species existing today. One common theory—that fish evolved from some wormlike life-form—is critiqued, documenting that the fossil gap between worms and fish is considerable and has never been bridged by fossil or taxonomic evidence. Additional theories, such as fish having evolved from a more complex invertebrate, are also evaluated and found to lack scientific evidence