Seldon's post above seems an utterly reasonable defense of polyamory.
I suspect the reason monogamy is so popularly recognized as the best way to go today is because of a strange interaction between tradition and the gradual liberation of women. Women as well as children were treated as property of the Patriarch by the Romans and other cultures, and this caused tendencies which haven't yet disappeared. To be property meant being obedient and being unable to make your own decisions. Therefore, to be "faithful" as a wife meant to be like property, and to be like property meant the wife could not decide to fuck anyone other than the husband: the husband would not make that decision, and so the wife couldn't act upon it as that ideal wife-as-property. This is how a "homewrecking" man could be seen as having transgressed against the husband of the wife he fucked: whether rape or simple sex, the man damaged the husband's property by lowering its worth to him as sexual exclusivity (in women!) is often valued by men and a woman who was exclusive but is no longer so would then be 'damaged' (or "damaged goods") at least as a matter of the logic of property.
The above is generally thought of as a rather horrible view to have about women today. But we are not yet without its effects: we ask, who wears the pants in the relationship, and by doing so refer to who is in control. And many women even prefer their man to be somewhat dominant in certain respects. There has been, however, two historical reactions against this attitude that has basically amounted to an opening of relationships generally, with more freedom to choose partners for both the man and woman, and the other somewhat less wholesome tendency for wives simply to demand of their husbands the same sort of strictures that had historically been imposed mostly on the woman in the relationship: now, couples don't exist as a master with a wife as his property, they consist of two people who own and claim certain rights over each other with the idea that the other does so as well. Now they both are each other's property, and this is the basis for ideas that oppose so-called sexual infidelity. Now both people are allowed to desire and demand sexual exclusivity of their partner, and feel 'betrayed' or 'transgressed against' when their partner does not meet that expectation: this is the legacy of women as property and the liberation of women has in some ways meant the subtle imprisonment of men along with the women rather than freedom for both.
I suspect the reason monogamy is so popularly recognized as the best way to go today is because of a strange interaction between tradition and the gradual liberation of women. Women as well as children were treated as property of the Patriarch by the Romans and other cultures, and this caused tendencies which haven't yet disappeared. To be property meant being obedient and being unable to make your own decisions. Therefore, to be "faithful" as a wife meant to be like property, and to be like property meant the wife could not decide to fuck anyone other than the husband: the husband would not make that decision, and so the wife couldn't act upon it as that ideal wife-as-property. This is how a "homewrecking" man could be seen as having transgressed against the husband of the wife he fucked: whether rape or simple sex, the man damaged the husband's property by lowering its worth to him as sexual exclusivity (in women!) is often valued by men and a woman who was exclusive but is no longer so would then be 'damaged' (or "damaged goods") at least as a matter of the logic of property.
The above is generally thought of as a rather horrible view to have about women today. But we are not yet without its effects: we ask, who wears the pants in the relationship, and by doing so refer to who is in control. And many women even prefer their man to be somewhat dominant in certain respects. There has been, however, two historical reactions against this attitude that has basically amounted to an opening of relationships generally, with more freedom to choose partners for both the man and woman, and the other somewhat less wholesome tendency for wives simply to demand of their husbands the same sort of strictures that had historically been imposed mostly on the woman in the relationship: now, couples don't exist as a master with a wife as his property, they consist of two people who own and claim certain rights over each other with the idea that the other does so as well. Now they both are each other's property, and this is the basis for ideas that oppose so-called sexual infidelity. Now both people are allowed to desire and demand sexual exclusivity of their partner, and feel 'betrayed' or 'transgressed against' when their partner does not meet that expectation: this is the legacy of women as property and the liberation of women has in some ways meant the subtle imprisonment of men along with the women rather than freedom for both.