I know a few happily married couples in "open" relationships. Poly or whatever you wanna call it. And I know a few unhappy, obviously sexless couples in traditional marriages as well.
For me, marriage is both an outdated and terrifying prospect. The thought of being with one woman for the rest of my life, sexually, is off-putting. So instead of doing what many others do - cheat, get caught, divorce, repeat - I just choose not to marry. Unless I find someone of a similar mind-set.
Dating sites are filled to the brim with women/men who want a "discreet" relationship. Instead of being open about our needs and communicating and accepting those needs, we choose to hide/vilify those who are brave enough to do. So as a society we keep up this fake appearance of "proper" when increasingly more and more are cheating, getting divorced, being miserable...why? Why is this necessary? I don't get it.
Sorry for ranting. It's just what you said struck a chord with me.
The problem with polygamy in a peaceful and prosperous society is there will be huge inequality between the most attractive and the least attractive in terms of the ability to find sexual partners, which will be a strong factor in social unrest. Potentially there is a correlation between countries permitting polygamy and terrorism. Monogamy and polygamy are two sides of the same coin. I think over time society will choose the one best suited to its current circumstance, but it can take a while.
Sex has been one of the major driving forces behind every decision I've made since I turned 13 or so. How I dress, how I talk, why I buy the things I buy and 50% of why I wake up at 5 am to go to the gym, why I go out to obnoxious bars and clubs... how is that not a 'need'? In the hunter-gatherer sense I guess it's not since I won't die if I don't have it but the want to have it as much as possible controls a huge percent of my daily actions. So maybe an 'addiction' then? Fine but now we're splitting hairs.
I would ague that marriage is not a need. It's an artificial construct that we impose on ourselves in a time when we don't need to do it. Women don't need you to survive, they can be their own providers now.
And why do you need to be betrothed to one woman for all eternity? Nature would love for you to spread your seed amongst many more women - larger bio-diversity.
But nobody is stopping you if traditional marriage is what you want to do, of course, more power to you.
While this is technically true, it's stated a little too glibly considering that we're talking about life-or-death (over the long term) evolutionary drives here.
One thing that has always bothered me is that almost any argument against polygamy works just as well as an argument against banning extra-marital sexual relationships.
As you said, polygamy already exists, just without the legal framework calling it a marriage.
Polygamy is a bad thing because it concentrates power, decreases equality for women and increases resentment by lowers status men, who have little hope of a happy life. Usually polygamy only create a small set of legitimate heirs and a larger subset of 'bastards' who also have little prospects in life within these societies.
Polygamy is actually a rarity in human societies, and while it definitely exists as a cultural practice, it's usually in a society with heavy restrictions on freedom. What is more usual is monogamous relationships with a small amount of adultery on the side. Given the choice of the two, the latter is arguably a better choice for societies, which is why it is the norm.
Polygamy is still occurring, except without the official status of wife.
Makes me wonder if the benefits of outlawing polygamy in the US might not outweigh the harm - especially because it happens anyway.