Both of these appear in the early chapters of Genesis, and both are indicative of seminal moments in the history of man - events clearly moving men farther away from God in enmity against Him. This first one is about the line of Cain:
Polygamy entered the picture with Lamech, who was the seventh from Adam through Cain and was representative of a society that was quickly sinking in depravity and growing in contempt for God's way of life! His sons represented those people with material talents, but not with the right focus.
This example of moving away from the closest thing to a sanctified God plane marriage relationship is very significant!
Hmm. Interesting, interesting. He is basically saying, Listen up, you inferior women! Don't you dare cross me! You better do what I say when I say it! I killed a man for something less so get in line. Here we see the prideful nature of the first occurrence of a man that took two wives. And we could just stop right here because I do believe that is the bottom line on top. There is not a whole lot of good that came from having more than one wife.