Are you saying God created incest?
The chromosomes hadn't broken down yet...even just a couple hundred years ago it wasn't unusual for, say, cousins to marry but it's anathema now.
I've read some of your comments on this thread. You really should try to tone down the cynicism when people come up with possible explanations based on the Bible. You claim that these people are saying they know everything about God and you judge them for self-righteousness. They are just coming up with possible explanations, many of which are based on scripture. I don't see anyone claiming to know everything.