For me in particular,
Polygamy = a most definite and adamant NO.
Abolishing anything - Yes, IF entails the eradication of ALL influences/interferences of Religions on Society at large.

A post-christian society is one in which fewer and fewer people believe, but the christian values are so imbued that they live on. I used to think a community of non-believers would take to behaving as our fellow large mammals. Not the case.

No. Men who intend to be monogamous cheat out of weakness. From losing an internal battle against innate feelings of attraction for the opposite sex. And it apples to both religious people an non religious people. If I had to pick a side, I would say atheists are better at this because they have more control over their minds.

I always thought Mormons had polygamy....why would you think we would?

The norms of human behavior come from our evolved heritage, religion merely takes what is there and gives the credit to the supernatural beings, because the priests who are employed in their name want them to have credit for everything, thereby getting more power and wealth to themselves. They should not be allowed to take credit for moral norms, any more than for making the rain fall. (Though they tried that too, because they could get away with claiming anything which people in the past could not understand.)

I don't think so monogamous lifestyle can be abolished. Sexual relationships come in different styles and it doesn't matter if a person is an atheist or religious. The great thing in a non believer community is that people try to be honest and clear about their sexual relationship preferences.
I was religious and now I'm a non-believer but I'm still feeling comfortable with the monogamous style and also I expect the same thing from a partner.

Here are some examples of sexual relationships styles and maybe somewhere are more styles.
Monogamous Relationships.
Polyamorous Relationships.
Open Relationships.
Long-Distance Relationships.
Casual Sex Relationships.
'Friends With Benefits' Relationships.
Asexual Relationships.

Zesty, we just have an arena where people can more openly discuss their proclivities and preferences. If such freedom existed outside of this site you would here more. There are communities where these topics are openly didcussed, but they are cloistered and guarded for the above reasons.

We are more open minded about desires of humanity. I have no problem with polygamy.

An atheist is more freely able to decide for themselves what life they want, monogamy, polygamy, etc. More what defines those positions resides in the society as a whole, and its attitudes towards interpersonal relationships.

I was an atheist for 25 years before trying polyamory. I reached a point where I decided that serial monogamy really hadn't worked for me and decided to try something different. So far it's been good for me except for those times when you get really into someone and get rejected because they just are not wired for or accepting of polyamory.

maybe in a few generations but maybe not. will be interesting to see

What does one thing got to do with the other?..... why do you think there is a correlation?

I read that there is a correlation between non-monogamy and intelligence. And atheists are generally more intelligent, and educated.

Esther Perel's book, "The State of Affairs," provides some interesting bits of the history and changes of monogamy.

That's called Mormon.

Most of the people I knew that was into poly relationships were religious. I have no clue how they rectified it within their religion since I never asked.

Also (though this wasn't asked), most of the people I knew that were into BDSM were also religious.

I find the whole poly thing very interesting, I would enjoy learning about it over a coffee.

it is living arrangments that confuse me the most, and etiquette.