... remember if there were any daughters. Wouldn't they have had to have incestuous relations to populate the world? Once we get past that explanation we get to Noah, wouldn't they had to of had incestuous relations as well. If that is so how could that have happened without it causing genetic defects in reproduction?
Yes Adam and Eve had other sons and daughters.Cain married his sister or a later female descendant of Adam through the marriage of any of Adam’s sons or daughters is viewed by some societies today as unthinkable. This is usually because of societal taboos or fear of genetic defects. Nevertheless, F. LaGard Smith comments in The Narrated Bible in Chronological Order: “It is altogether likely that these first brothers and sisters enter into marriages with each other, despite the sense of inappropriateness which would be felt should that occur in following generations.” Also, it is noteworthy that it was not until Moses received God’s laws for the nation of Israel in 1513 B.C.E. that intercourse between such close relatives was specifically forbidden.