You claim to know genetics and don't know that today's incest is entirely different than Cain marrying his sister? When the first two people were created, they were perfect. Everything God made was “very good” (Genesis 1:31). That means their genes were perfect, no mistakes.

Scripture makes the fact very clear and it is stated in both the Old Testament and the New Testament. Genesis is the book of beginnings. It is the place where we find the truth of the beginning of man and that man is Adam. The word "Adam" comes from a Hebrew word that means red or ruddy. It does NOT mean that he was white! The word “Adam” is translated as; first man, mankind, man or human. God made Adam from the "dust of the ground", which is the Hebrew word "adamah" and therefore Adam's name comes from the ground from which God created him.