If you believe in Christianity then you believe in incest. Adam and Eve had two sons Cain and Able. Cain killed Able then was banished. Then they had the 3rd son Seth (they had more kids but Seth is last mentioned I believe by name). Seth (and his siblings) would either have to have sex with his mother or sisters to spawn the human race. So how did these humans reproduce without incest according to Christianity??
I'm not sure how to address the rest of your post, but this is not really a tough question to consider. In the beginning of creation, everything God made was good. There was no death, no disease, no mutations of any kind. The human genome was completely clean. When mankind decided to sin, that sin brought all those things into the world (death, disease, etc.). The human genome was then prone to corruption. It wasn't bad at first, which is why God allowed incest to increase the population. But many generations later, God saw that it kept getting worse, so in Moses' time He finally commanded that incest should stop. Not only was it dangerous, but it wasn't necessary anymore.
I highly doubt this will do anything to change your opinion, but I figured it should be addressed anyway.
"Jesus said to him, 'I am the way, the truth, and the life. No one comes to the Father except through me.' " ~John 14:6 (NKJV)
