Generations of literalists who’ve had their eyes opened by reading what the Bible actually says have stumbled over Cain. His murder of Abel is fine—predictable even. The problem is what happens after that. Since he has murdered his brother, the only other human born so far, Cain seems prematurely concerned about “every one that findeth” him killing him. Seems unlikely that Eve, or even Adam, would like to kill the only surviving child they have. Yet God puts a mark on Cain. Presumably his parents would recognize him, so why is Cain literally a marked man? Rather than Omega Man survival techniques, Cain focuses his attention on kick-starting his love life.
Cain’s wife immediately raises the issue of where the girl comes from. Those who like to call themselves literalists have to back-peddle a little and suggest that since, according to Genesis 5 Adam and Eve had other children, this must be where she derives. Of course, she would in such a scenario, be his sister. Extraordinary circumstances call for extreme measures, but even so, literally, there are no other people yet. Cain is old enough to kill his brother and the next child born, according to the narrative, is Seth. Seth is explicitly a replacement for Abel, and really he doesn’t do Cain any favors in finding a wife. The story here simply slips out of character and gives us a world already partially populated.
As I was tweeting Genesis 4, it occurred to me that immediately after marrying, Cain builds a city. Cities only sprang into existence to allow for mutual protection with the diversification of labor, following on from the agricultural revolution. One of the main characteristics of cities is population. Genesis 4 has only Adam, Eve, Cain, his wife, and Enoch. It may be the smallest city in history since the entire human race could have easily fit into one modest house.
The stories of Genesis are etiologies—tales of origins that have no ties to historical incidents. Cain represents the urbanites, the city dwellers who will always somehow find ways of irritating God. In our urban culture where most people are born in towns or cities, we have lost touch with the life of the nomadic pastoralist. We are, however, merely following the literal path that the Bible lays out for us. As we shall shortly see, the children of Cain and Seth are the same.