> From a practical standpoint, widespread polygamy (which usually means polygyny) can lead to imbalances in marriage opportunity
So can widespread monogamy in certain circumstances. In fact, that's pretty much why polygamy usually manifests as polygyny -- in societies with norms favoring men fighting, or engaging in other high-risk activities and protecting women (and children, usually, but while that's important to the motivation, its irrelevant to the effect), after certain types of events, such as large scale (for the community affected) conflict, an exclusive monogamy rule means most women have no mates and prevents a society from rebounding (and makes it more likely that there culture will die out).
This is also probably why in history polygamy loses acceptance as a general norm as the scale of society gets larger and these kind of events affecting a whole society become less common.
So can widespread monogamy in certain circumstances. In fact, that's pretty much why polygamy usually manifests as polygyny -- in societies with norms favoring men fighting, or engaging in other high-risk activities and protecting women (and children, usually, but while that's important to the motivation, its irrelevant to the effect), after certain types of events, such as large scale (for the community affected) conflict, an exclusive monogamy rule means most women have no mates and prevents a society from rebounding (and makes it more likely that there culture will die out).
This is also probably why in history polygamy loses acceptance as a general norm as the scale of society gets larger and these kind of events affecting a whole society become less common.