https://cei.org/content/how-ideas-family-evolve-alongside-culture-politics-and-law
What I'm surprised they don't say is that line marriage is more of an
old idea brought back than a new one.
The modern welfare state, and with it the old age pension (both first
created by Bismarck in 1871) are what made possible the breakup of the
extended family and its replacement by the nuclear family. Thus,
conservatives should think twice before declaring multiple marriage a
bad idea.