Depends how much you've got to go around doesn't it? PMSL
And I'm not looking at it from a gender perspective necessarily - females just tend to get on better in groups by and large - one cockerel in a henhouse tends to do OK for instance
So the multiple spouses concept isn't gender-specific except by custom (one woman or man to many of the opposite sex) and I was looking at it from a 'viability' PoV where there is a legal contract in place (not necessarily marriage but 'official' as it were since many countries only recognise the trad hetero coupledom) and not 'adventures' outside of the contractual parties...?
Now I'm getting confused too - what would happen if all involved in the contract were allowed as many spouses as they wanted? Or were homosexual or bi-sexual? *screams in confusion*
I've merely cited the more common male singleton/female poly-way and not necessarily from the sexual aspect, to whit -
As for polygamy and harems - you always know who the old man's with and where; have back-up if you have a headache/have to wash your hair/need a bloody good gossip and at least a couple of nights off a week... plus you always have someone to go shopping for shoes with and/or talk to instead of having to listen to non-stop drivel about football (any sort) or how great the new car is?
Based on female physiology and social tendencies...
I'm sure there are non-sexual advantages the other way around too - it's just from personal obvservations down fifty-odd years males tend to not to like to share so much...
EDIT - which, by a circuitous route, kind of brings us back onto topic again on the point that women are possibly less keen on war-mongering than men. Something I think we were actually getting a consensus on before the attractions or otherwise of polygamy intervened...
Speaking only for myself and again from bitter experience, one husband is more than enough trouble and effort for me and frankly I'd far rather have a cup of tea - and a choccy hob-nob of course