A scientific theory isn't a "guess" in the way you mean theory - it must go through a lot of testing and be based on repeatability and corroboration.
The trouble with creation myths is to decide *which* creation myth to feature - you are aware, are you not, that there have been thousands of these throughout history? I have studied these - and some are a hoot! They may be interesting to know, but they are not EVEN theory - they're all myth.
And there's absolutely no doubt we are descended from apes.