Contrary to what most people may believe, evolutionarily speaking, the institution of marriage between one man and one woman actually benefits men more than women. Most men believe that polygamy would be better for men because men are "horn dogs" and all they want is tons of women for themselves. However, if polygamy were the socially appropriate mating style, men would loose on the deal. Here is why:
First, here are a few facts:
1.) Women are much more likely to be a biological parent than are men. How can this be you may ask? Its simple, look at the next facts:
2.) Men and woman both often have multiple sexual partners (this fact may be obvious to most people).
3.) Woman can be absolutely sure that the child(ren) they care for are their own. Men do not have that certainty. If a woman has unprotected sex with more than one man (especially during ovulation) she will have a child that is most certainly her own. However, a man can have unprotected sex with as many women as he wants and is not guaranteed to father a child (biologically at least). Therefore, monogamy protects men from providing resources to children that are not his own. A woman does not have to worry about this since if the child comes out of her womb it is most certainly her own.
4.) In world where highly disproportionate amounts of resources are dispersed between individuals, i.e. only a few people hold all the wealth, if polygamy and or polyandry were socially appropriate and it where the norm, it is likely that harems would emerge. This would be bad for most men on all fronts (evolutionarily at least). In the case of polygamy, there would only be a few happy men and there would be many unhappy men because most of the men with the most money would have several wives, leaving no wives for the poorer men. This would be a recipe for disaster, since studies have shown that men are married or partnered have fewer problems and are generally happier. Indeed, a chemical is released in the male that has calming effects; it also decreases testosterone in the male. The case of polyandry is obvious since only one man of the many, could father (biologically) a child. Essentially, not only would polygamy and or polyandry be bad for most males, it would likely be bad for society since there would likely be more aggressive crimes etc.
It should be noted that most women would reply to this argument by saying that women would never go for it... however, in a world where one individual's income could provide for 100's of wives, it is not inconceivable. Indeed, if the social stigma against polygamy and or polyandry were removed, there would not be much from preventing this from happening on a large scale. Sure, the wives would be jealous of the other wives, but evolutionarily speaking, the increase in resources would overrule that jealousy.