"By virtue of being Cain's descendants, the people named in the genealogy all inherit his curse. Thus the Cainite genealogy becomes part of the Yahwist's account of man's increasing sin."252
Cain's wife (v. 17) was evidently one of his sisters or nieces (cf. 5:4). God did not prohibit marrying siblings and close relatives until the Mosaic Law.
"Because harmful mutations so greatly outnumber any supposed helpful ones, it's considered unwise nowadays (and illegal in many states) to marry someone too closely related to you. Why? Because you greatly increase the odds that bad genes will show up. By the way, you also increase the odds of bringing out really excellent trait combinations. But did you ever hear anybody say, Don't marry your first cousin or you'll have a genius for a child?' They don't usually say that, because the odds of something bad happening are far, far, far, far, far greater.
"That would not have been a problem, by the way, shortly after creation (no problem for Cain and his wife, for example). Until mutations had a chance to accumulate in the human population, no such risk of bad combinations existed."253
Lamech (v. 19) was the first bigamist. Bigamy was common in the ancient Near East, but it was never God's desire (cf. 2:24; Matt. 19:4-5). God permitted it, however, as He did many other customs of which He disapproved (e.g., divorce, marrying concubines, polygamy, etc.).
"To be sure, no rebuke from God is directed at Lamech for his violation of the marital arrangement. It is simply recorded. But that is the case with most OT illustrations of polygamy. Abraham is not condemned for cohabiting with Sarah and Hagar, nor is Jacob for marrying simultaneously Leah and Rachel. In fact, however, nearly every polygamous househould [sic] in the OT suffers most unpleasant and shattering experiences precisely because of this ad hoc relationship. The domestic struggles that ensue are devastating."254
"Cain's family is a microcosm: its pattern of technical prowess and moral failure is that of humanity."255
God showsthe destructive consequences of sin (cf. 2:24) more often than He statesthem in the Old Testament. Polygamy is one form of sin.
Polygamy is ". . . the symptom of an unbalanced view of marriage, which regards it as an institution in which the wife's ultimate raison d'etre[reason for being] is the production of children. Where God had created the woman first and foremost for partnership, society made her in effect a means to an end, even if a noble end, and wrote its view into its marriage contracts."256
This is the first occurrence of polygamy in Genesis. We shall find several cases of it throughout the Old Testament. People practiced it widely in the ancient Near East, but it was contrary to the will of God (2:24). Beside indulging the flesh polygamy was an attempt to ensure the survival of the family by providing male successors.257
The reference to forging (lit. sharpening) iron implements (v. 22) appears anacronistic since the smelting of iron was not common until the Iron Age, in the second millennium B.C. Perhaps this is a reference to the cold forging of meteoric iron, which was common earlier.258
We could paraphrase the idea in Lamech's mind as expressed in verses 23-24 more clearly as follows. "If I am threatened again, I will retaliate again, even more forcefully than Cain did."Lamech may have been claiming that he had killed in self-defense.259Nevertheless he was boasting and shows himself thereby to be more barbaric than his forefather Cain (cf. Exod. 21:25). Many commentators have called Lamech's poem the "Song of the Sword."Lamech thought himself invincible with his newly acquired weapons.
"Both Cain's antediluvian lineage and the postdiluvian Babel cautioned later Israel that cities founded upon arrogance resulted in violence and ultimately destruction."260
