Bury me smilin’ on YouTube asks, “If Adam and Eve had Cain and Abel, then how did Adam and Eve’s grandchildren come about?” Well, thank you for your question, but the answer can easily be found in the Genesis account: “Cain made love to his wife, and she became pregnant and gave birth to Enoch” (Genesis 4:17). As one would expect, this answer leads to other questions, so I will do my best to answer a few.
First, who was Cain’s wife? Well, obviously this would have been a close relative, perhaps a sister or a niece. At first glance, you might rightly assume, “Oh my goodness; that’s nasty.” But how is that any more revolting than the Darwinian alternative of a single common ancestor? Never mind that, but the biblical account pales in comparison! But let’s think about this intellectually, rather than emotionally.
If God wanted Adam and Eve to populate the entire world, this sort of thing would have been unavoidable; the real question is whether it would have caused the same types of problems we encounter today? I would argue, “No.”
The biblical text tells us that people in Adam’s day lived to be a thousand years old, so how is that? If these were the first humans, or close to the first, then they would have been almost genetically perfect. We wouldn’t expect the same types of problems as we do today. Moreover, think of how many people that could be produced by a single couple in a thousand years; that’s half the time since Christ was on this earth. That’s a long time. Think of all the people that have reproduced since that time; that’s a lot of people. Not only would this be possible; it might also be probable, especially if modern day genetic issues were non-existent.
Even if God allowed, or planned, for close relatives to procreate, He only did so for a limited amount of time, up until He gave the law to Moses. Perhaps that’s because the DNA became too degenerated as a result of sin and death in the world. But after a certain point, God commanded against these types of relations, as noted in Leviticus 18. This seems to make sense, considering the problems that now occur in closely related relations. Clearly God was ahead of the game, long before we had a single clue as to what DNA was. And since He now commands against it, it’s immoral to do otherwise, something Darwinism can say nothing about.