Basically from what I've read, it's been culturally natural for men to have multiple wives/women if they can protect or provide from them.
As far as women go, ideally they only want 1 partner, but they will pursue multiple partners if they can't get "everything" in one package - as is the case with the stereotypical women who settles for a beta provider, but carries on an affair with a young stud, subconsciously hoping to get the young stud's "genes" but the beta provider's "support". Though if she's married to a guy who's a total asshole or abuser then she may carry on an affair with a more "sensitive guy".
Basically:
*Men naturally want to have numerous women, but are less picky about the women they do have
*Women naturally prefer to have just one man, but are more picky about the man they have
As far as women go, ideally they only want 1 partner, but they will pursue multiple partners if they can't get "everything" in one package - as is the case with the stereotypical women who settles for a beta provider, but carries on an affair with a young stud, subconsciously hoping to get the young stud's "genes" but the beta provider's "support". Though if she's married to a guy who's a total asshole or abuser then she may carry on an affair with a more "sensitive guy".
Basically:
*Men naturally want to have numerous women, but are less picky about the women they do have
*Women naturally prefer to have just one man, but are more picky about the man they have