Cain and his offspring build civilization (Genesis 4:17-24)

Cain and his offspring give birth to civilization. He’s the first to be seen building a city. His direct descendant Jabal seems to be a rancher or farmer. Jabal’s brother, Jubal, is the first musician. And another descendent of Cain, Tubal-Cain, is a blacksmith.
Lamech, the father of Jabal, Jubal, and Tubal-Cain, kills a young man, committing the second recorded murder (4:23). But then he goes beyond Cain’s misdeed by becoming presumptuous and arrogant about his crime. Cain concealed his murder (4:9), presumably feeling at least some guilt about it. But Lamech calls together his two wives (he’s our first polygamist) and announces that he’s committed murder. And this is no act of contrition; it’s his opportunity to mimic the words of God (4:15) when he says “If Cain is avenged seven times, then Lamech seventy-seven times.” Who proclaimed the punishment for harming Cain? God. Who proclaimed the punishment for harming Lamech? Lamech. Lamech is an arrogant murder who does not hesitate to take the place of God as an avenger.

It’s suspicious that civilizations springs up among the descendents of muderers.