Evolution is a scientific theory; that means that

1. It's based on facts, like:

    1. Mutation, that you can see mutations everyday, from
       a microrganism to a whale.

    2. The natural selection, that can you also can see
       everyday.

2. Its predictions can be tested.

   1. For example with help of genetics. 

3. It's falsifiable, that means you can try to build a test to refute the theory, but this test must be fact based.

Creationism isn't a scientific theory because you can't bring the facts. Show reproducible facts and then we can discuss.