bore me to tears

1. When Genesis 4:17 reports that, “And Cain knew his wife, and she conceived and bore Enoch,” we cannot assume that it was Eve that bore Cain’s child.  Given their long lifespans (Adam lived for 930 years, as you recall from Genesis 5:5), Eve had many years to produce a daughter/sex partner for Cain.  In fact, all of the best scholarship on this matter points to a likely brother-sister pairing.
2. Incest was not only permissable, at one time; it was God’s Plan to grow his family. It was only later, in the time of Moses, that God prohibited the practice (Leviticus 18).

None of you shall approach anyone who is near of kin to him, to uncover his nakedness: I am the Lord. The nakedness of your father or the nakedness of your mother you shall not uncover. She is your mother; you shall not uncover her nakedness. The nakedness of your father’s wife you shall not uncover; it is your father’s nakedness. The nakedness of your sister, the daughter of your father, or the daughter of your mother, whether born at home or elsewhere, their nakedness…
(See Leviticus 18:7- for more, as this goes on for quite some time. Basically, nakedness = bad.)

Now, I know what you’re thinking:  That’s not possible.  God’s Truths are timeless and unchanging.  His requirements of us do not bend to the times, like the corrupt “situational ethics” of mealy-mouthed, values-neutral liberals.  God’s Truths remain constant over time:  What is wrong is wrong today - just as it was yesterday – and will be tomorrow. 

Instead, the trick to thinking about Cain’s wife is flexibility

and what I call religious word play - in this case, with the word, “bad.”

You may associate “bad” with the following synomyns:

depraved, corrupt, base, sinful, criminal, atrocious

Sure, “bad” may be used in this way when describing, oh, homosexuals, for instance; but, when it comes to describing First Family incest, you’ll need to rethink the word.  It’s sorta like redefining the word “is.”

It depends on what the meaning of the word 'is' is.

You see, in the case of the brother-sister sex predestined by God, the idea was a fine one (”very good” even); it was only later, post-Fall, that incest became bad-unhealthy. 

The following account (accepted by many fundamentalists) explains how it all went down:

Now it is true that children produced in a union between brother and sister have a greater chance to be deformed. As a matter of fact, the closer the couple are in relationship, the more likely it is that any offspring will be deformed. It is very easy to understand this without going into all the technical details.

Each person inherits a set of genes from his or her mother and father. Unfortunately, genes today contain many mistakes (because of sin and the Curse), and these mistakes show up in a variety of ways.

However, this fact of present-day life did not apply to Adam and Eve. 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. But when sin entered the world because of Adam (Genesis 3:6), God cursed the world so that the perfect creation then began to degenerate, that is, suffer death and decay (Romans 8:22). Over a long period of time, this degeneration would have resulted in all sorts of mistakes occurring in the genetic material of living things.

But Cain was in the first generation of children ever born. He, as well as his brothers and sisters, would have received virtually no imperfect genes from Adam or Eve, since the effects of sin and the Curse would have been minimal to start with. In that situation, brother and sister could have married (provided it was one man for one woman, which is what marriage is all about, Matthew 19:4–6) without any potential to produce deformed offspring.

By the time of Moses (about 2,500 years later), degenerative mistakes would have accumulated to such an extent in the human race that it would have been necessary for God to bring in the laws forbidding brother-sister (and close relative) marriage (Leviticus 18–20).

Related posts:

Where’d Cain get his wife – Part I
Bible-bases marriage