Polygamy - polygyny (having many wives) - was traditionally beneficial to women and very bad news for those men who did not have lots of land/money.
The reason being that women could share the wealth (and the benefits associated with that) of a rich husband.
In the Old Testament, in its laws dealing with polygamy (the only "acceptable" version of which was polygyny as it was deemed "adultery" if a married woman had sex with any man other than her one-and-only husband), importance was placed on the husband being able to provide for all his wives equally and well - no man was allowed to have more wives than he could afford to keep and he was not to shirk his responsibilities to any one of them nor to his children by any of them in favour of another wife/child.
So, if a man had sufficient wealth to support more than one wife (and being rich, he's sought after by women as being a good provider for the woman and any children), more women in the area could benefit from that wealth. Instead of just one lucky woman landing the one guy in twenty miles with enough money to provide for a family, two or more women and their subsequent children could prosper.
Bad news for the large number of poorer blokes who suffer the shortage of women.
As to the man with the multiple wives - he's got even more responsibility than a man with a single wife.
Stupid people go "ooh, lucky devil, eh, gets to fuck lots of chicks, can pick and choose if he gets bored with one."
Well, it's not quite that simple. He has responsibilities to give emotional and financial support to all of those women - even if he's not bound by the laws of the Old Testament, he has a moral obligation to them all (and if our current laws permitted polygyny, he'd have legal obligations under our contemporary matrimonial laws to all of them as well.)
Then there's polyandry - a woman having multiple husbands (not popular in areas where the Old Testament holds sway because it runs afoul of the OT's definition of "adultery") and general polygamy where either sex can have as many spouses as they can manage - which gives rise to what we nowadays call "polyamory".
But in all of the above, it's not just about sex with multiple people (you can do that without the hassle of getting married to even one) it's about responsibilities and fairness, doing right by them and honouring your commitment to be there for them in all ways.
edited 17th Apr '13 5:27:22 AM by Wolf1066