I'm afraid what you're saying isn't true. Even Elvis Presley sang it in one of his songs Kissin' Cousins. He sings, "Yeah we're all cousins. That's what I believe, 'Cause we're all children, Of Adam and Eve."
And who are we to question the eternal wisdom and knowledge of the King of Rock 'n Roll?!
You're not putting enough faith in the capabilities of God.
And you're not putting enough faith in the capabilities of Spder-Man. Or science, for that matter.
With all due respect, you sound as bad as the Muslims who say that the one who God said He would send would reveal things to them in the New Testament has to be Muhammed and not the Holy Spirit because they don't have enough faith to believe that God could've had foretold what would happen in advance.

I looked back in the account of Lot. According to that, his daughters were the once who had sex with him and got pregnant; and he didn't even know it because he was asleep. For all I know, he might've thought he was having a wet dream or something. They did it because they had lost their husbands, and they needed someone to carry on the family line as it was their custom. It's in Genesis 30.
God bless, Jason Irelan
You found references to incest in the bible. What a stroke of luck!