How does the Darwin's evolutionary theory and the big bang theory disprove the intelligent design theory ?

I've been wondering this for a while because to my knowledge theorys have yet to be proven themselves. Also these two theorys describe the processes by which things may have happened to make things as they are now. Where as intelligent design states that something intelligent caused it to happen. It would be like saying that a dinner table wasn't man made due to the fact that we can explain how it was made. It seems to me that evolution and the big bang theory in fact support intelligent design because it seems to me that if something intelligent did create everything that other intelligent beings would be able to explain how it was done. And If it wasn't done by something intelligent we probably would be unable to explain it. The sky would be green the ground clear that type of thing.