What I think of incest & the Bible: Adam and Eve were created perfect in every way. Their children were also born physically and genetically perfect. Cain's wife then, could have been one of his sisters with no problems. (Likewise, many of Adam & Eve's children would have inter-married with no problems.) God had to temporarily allow intra-family marriages to increase the population. However, God does not condone near-relative marriages. If God's command to Israel ("None of you shall approach anyone who is near of kin to him, to uncover his nakedness: I am the Lord." ) (Leviticus 18:6)
been given to Adam and Eve, and they and their children all obeyed it, mankind would have quickly died out. According to the Bible, all people are descendants of Adam and Eve...all are of “one blood.” (So, if you don't marry a relation---you don't marry a human.)
Sheryl brings up a good point. God is God and can protect humanity. Adam and Eve were perfect until
they sinned. We can be a new creature in Christ, turn around and denounce the very existence of God, and become corrupt in our own pride and arrogance. What God made was "very good", but sin corrupts. Adam and Eve were made perfect, but had free choice to stay that way....which they did not
Again...the "Law" was handed down to Moses to man. Before that, it was a different dispensation with different variables which man lived and died. What kind of "Law" was there then? We don't know. However, man is known to make his own rules regardless of what God wants for him. Today we are different races, blood types, genetics, etc. Why? because after the flood, the 3 sons of Noah's offspring got divided in the earth. There is nothing to tell the races of their wives, or themselves to be honest. Also, at the tower of Babel, God changed the main language into different languages, dialects, etc., so that also contributed separating the people further into their prospective races, tribes.