It's real, and not fully understood. Without it, there would be no field of biology. There is simply too much evidence and it provides too much explanatory power to be wrong. Bacteria rapidly reacting to new, synthetic chemicals (new information), ring species, etc… it lines up too well to the data to be far off target.

The fundamentalist mindset rejects it in several incoherent ways:

1. Rejecting that new information can happen in the process of mutation (obviously and demonstrably false)
2. Rejecting that enough time has happened for speciation (yet accepting that all of the species we see came from a handful of original species on the Ark 4000 years ago)
3. General rejection of fossil evidence
4. Rejecting science (…and then telling the world via computers, using phones, driving cars, flying, taking medicine…)

Catholics accept it. Mainstream protestants accept it. The only areas that reject it are fundamentalist.

Rejecting Macro-Evolution