The problem with the theory of evolution
It was formed before people knew about DNA.
DNA is basically an instruction manual for a being to grow, form, and function. If there is mutation, it is the absence of information, and mutations are always bad.
For a good mutation to take place (evolution), the entire DNA strand would have to rewrite itself into a new, perfectly ordered and working strand. For that 'evolved' animal to not be a one off, there would have to be multiple spontaneous evolutions at the same time, creating a bunch of animals to mate and continue the new species.
Let's face it, that just can't happen.
Gradual change may occur within a species, but to create a brand new species, that just cannot happen.