By the time we get to this passage it seems evident that Yahweh created Adam and Eve with not only the ability to speak Hebrew, but also the ability to employ complicated wordplay within that language. In 2:23 the man uses a play on ishah (woman) and ish (man); in 3:20 he uses a rather complex play on khavvah (Eve), khay/khayyah (living), and khayah (to live); and now in 4:1 Eve uses wordplay on the sound of the verb qaniti (I have created/obtained) and the name qayin (Cain).
This is odd because the narrative strongly suggests that literary devices are being employed by a story teller, not actual history being recorded. This becomes even more apparent when we find in verse 2 that Eve names her other son Abel, which means “breath” or “vapor” in Hebrew. Eve provides no stated reason for giving him this name, but it serves as an obvious literary device that points to an ominous foreshadowing of events that will follow. This will happen again and again throughout the pages of the Bible. People will be given names, the meanings of which will amazingly often foreshadow events that will take place later in the narrative accounts of their lives or will point to some specific characteristic of that person. I'm sure people will say it was because God providentially worked out these naming choices to reflect events that he knew would occur later in their lives, yet in every other piece of literature one would naturally assume such a feature was the mark of fictional story-telling. Why should the authors of the Bible get a pass?
In this passage where Cain and Abel bring gifts to Yahweh, the straightforward reading gives every indication that Yahweh’s presence is still visible and unmediated. How does Cain know that Yahweh didn’t like his offering? The passage literally says that Yahweh gazed (sha’ah) at Abel’s offering, but did not do the same to Cain’s. Cain knew which gift Yahweh liked better because he saw the expression on Yahweh’s face. Note that Yahweh speaks to Cain in a conversational manner as well. It would seem that nothing about the way Yahweh interacts with mankind has changed since the fall. He still comes across as very humanlike and his presence appears to be unmediated.
It’s only when one approaches the text with preconceived notions about God’s invisibility, transcendence and holiness that one is able to read this passage and conjure up images of Cain and Abel standing before stone altars that are never mentioned in the text, looking heavenward instead of directly at a visible manifestation of God, hearing an inner voice rather than an audible one, and Cain just somehow knowing intuitively that God didn’t like his offering rather than actually seeing him gaze approvingly at Abel’s offering and not his own. The escape I've seen most expositors use is to posit a pre-incarnate Christ and ignore all the additional exegetical and theological problems such a solution entails.
After Cain kills Abel he’s let off rather easily and is not only given a light punishment, but also special protection (apparently from his future siblings, nieces and nephews). As part of his punishment, Yahweh tells him that he will be a wanderer. Yet in verse 17 after getting his wife/sister (or maybe niece?) pregnant, he settles down, builds a city and names the city after his son? So in addition to “on that day you will surely die” we can add “you will be a vagrant and a wanderer on the earth” to Yahweh’s failed threats and empty promises thus far. We also see more Hebrew wordplay in Cain's naming the city “Enoch,” which means “dedicated.”
This is clearly the stuff of legend on the order of Romulus and Remus. People don’t just decide to found cities. You need a densely populated area, differentiation and specialization among that population (i.e. not everyone is a farmer/herder), centralized power, taxation, public buildings, record-keeping, craftsmen and most importantly trade. Just how did Cain come upon all these necessary components for a city when the only people on earth were his siblings, children, nephews and nieces? On top of that he’s supposedly cursed, is a known kin-slayer and has difficulty cultivating food. Who among his relatives is going to say to themselves, “I want to go start a civilization with that guy”?
In this passage we encounter the descendants of Cain who provide the origin stories for nomads, musicians and metallurgists. Again, this is the stuff of etiological myth. We’re supposed to believe that single individuals founded these vocations? Jabal just figured out tent-making and animal husbandry on his own? Jubal just decided that it would be cool to put some strings across some bent wood and make a harp and then hollow out a stick and make a flute and then invent music? Tubal-cain just happened to stumble across some copper ore, decided to melt it down and make tools out of it and later figured out that if he added tin to it he could make it vastly more durable, even though copper and tin ores are rarely found together? And what are we supposed to make of all these “he was the father of those who” pronouncements when it comes to the fact that they and all of the rest of Cain’s line were supposedly wiped out in the flood?
What if the originator of these portions of Genesis didn’t know that someone was going to later add a story about a universal flood? If fact, what if this story bears hints that it was originally part of a version that had Cain as the progenitor of this author's culture? Then it doesn’t really have to make sense or have continuity at all, does it? We can take it for what it appears to be, a collection of stories that circulated in Hebrew culture that were at some point written down and edited together in a way that doesn’t always fit the continuity.
Here Eve continues to make sophisticated Hebrew puns when naming her children, noting the approximation between the name shet (Seth) and the verb shat (to grant). I suspect stuff like this made remembering the stories easier for ancient story-tellers.
11 Now, this will sound strange, and even cruel, but it is the truth: Abel’s murder was not only the first in human history, but for that very reason the most mirthful; for Cain had absolutely no idea how to commit it.
12 From dusk till dawn he attacked Abel in the most fruitless of ways; he blew upon him; he strangled his hair; at one point he spent two hours simply shouting “Die! Die!” at Abel from various angles.
13 Fortunately for him, Abel was equally ignorant of how to fend off a murderous attack; neither defending himself nor running away, but making what in retrospect proved the tactical blunder, of lying perfectly still.
14 Ah…thou canst not make this stuff up.
15 Eventually Cain made use of a rock; but rather than throwing it at his brother, he picked up his brother and threw him at it, he did this 50 times, until Abel finally succumbed to a preexisting heart condition.
16 But in intent it was murder, and afterward I did indeed ask Cain of Abel’s whereabouts, and he did indeed reply, “Am I my brother’s keeper?”
17 Thus did Cain also invent sarcasm; and lo, who is not eternally grateful to him for that.
-Againesis 6:11-17, The Last Testament: A Memoir by GOD