Do you support the legalisation of polyagmy and polyandry

[toro]

1-How is a single person going to include fairness into this relationship? Say, I have a wife, and she gets old, and I take up a new, younger wife. I suddenly stop showing attention to my old wife and start sleeping with my new one all week long.
Obviously, the point of such marriages are nothing but the animalistic suppression of carnal desires, and have nothing to do with commitment.

What will stop it? The same thing stopping a person that loses interest in his/her older spouse in favor of younger, more "attractive" people and divorcing them. If we make divorce illegal, they won't divorce, but separate and cheat. If we make cheating illegal we are now legislating private behavior.

2-The children that are born from different mothers will obviously be in great confusion regarding the world around them, especially in places where monogamy has been traditionally practiced.

Just as you previously claimed children of a multi-racial/multi-ethnic family would? Or of a marriage between parents of the same sex? Or of parents of differing political/philosophical/religious views?

Study after study shows that children that are treated properly and cared for (without introducing sexual contact with adults) will grow up and be well adjusted towards others. The only "flaws" they may have is having a general predisposition towards accepting the behavior and views of the family they grew up in. So, in short: no, they won't.

3-Another obvious flaw is that such marriages tend to be emotionally abusive towards the partners who are amongst the multitude. Like I said, many marriages break apart due to a side claiming that he/she is not shown enough attention by his/her partner, how is a marriage based on a single-multiple partnership going to survive other than by force?

That's a good point. I'm sure any correlation between the fact that most if not all of such marriages tend to occur in highly religious and intolerant communities that also have a tendencies to have much higher rates of physically and emotionally abusive relationships and poor rates of sexual equality in single partner marriages is just coincidence. Right?

Only in primitive societies where women are seen as belongings, this type of marriage is still prevalent, and these are generally women who have been forced into accepting a second or more wives, to share their men with.
How is this going to work on the basis of "mutual consent"? Obviously, one or multiple partners will have to suffer emotional abuse if such a "marriage" is to be continued, for I really wonder how many people are willing to share their men, or women. But they would have to cope with it if they are forced into it, yes? That is it. Polygamy rests on the shoulders of inequality and abuse. It has been so for many years.

You seem to be focusing on the correlation between the social pressures of the societies and the prevalence of such marriages while ignoring the correlation between such societies and other behaviors. As result, you are assigning a causative relationship between the two when the causative relationship is likely due to the factors you are ignoring.

IMHO, the reason the prevalence decreases in more tolerant societies is simply because it is much harder to have such stable relationships. Not because the relationships themselves are bad. In recognizing this, people tend not to want to have them, and for this reason they don't form them. This is also ignoring the great legal difficulties in a multi-partner marriage. I'm sure they were initially outlawed for the same reason as #3: people associated the relationship with the society they didn't like.

Difficulty should not be a reason to outlaw things though. Otherwise, maybe we should outlaw multiple child families. I mean, what's to stop parents from having a new baby once they get bored with their 12 year old and giving them all the attention?

Personally, if that's what people want to do, go for it and enjoy yourselves for whatever reason you want: more family income, bigger dinners, more Xmas presents, more interesting sex... Whatever.