Civilized Behavior

I was reading a post at The Volokh Conspiracy about step-father, step daughter incest. A commenter noted that 5,000 years of civilization proves that this is a bad idea. Actually it doesn't. Here is my comment on why:

Did some one mention 5,000 years of civilization?

It was not uncommon for Pharoahs of Egypt to marry their biological sisters.

I don't think that bears on the current issue in the 21st Century, but one must remember that civilized people have had some strange ideas from time to time.

In the ME first cousin marriages are not uncommon. I don't know about uncle/niece marriages. Of course there are many who say the ME is uncivilized and I might tend to agree.