Monogamy has a long history rooted in social status and political maneuvering. Nomadic humans used marriage as a way to establish family ties that would save lives in times of crisis, specifically food shortages. When technology advanced far enough that people could store their food and wealth and pass it along down the generations, marriage was a way to legitimize the property transfer process. Fast forward thousands of years to Medieval England where the Catholic church struggled with the Anglo kings for political control. At this time it was common for marriages to be made and dissolved between clans as was politically expedient. By declaring marriage a Holy Sacrament, the Catholic church forced all future political contracts to be subjected to its approval. This is where the moral notion of monogamy arose.
Along with its moral imperative, the history of western marriage means monogamy comes with several other assumptions about what it means to be in a relationship. Among these are the notion ownership and control over another human being as well as the idea that being in a relationship with someone somehow prevents others from initiating a similar relationship with that person.
Belief in ownership of another human being leads to behaviors that are hurtful to the person being viewed as property. Traditionally when marrying, a woman became property of her husband. The two became “Man and Wife,” further reducing the woman from the category of a human to the category of being related to a man. To her, the man was her livelihood and just as she was his property, both had reason to defend their relationship against outsiders. Other women become enemies, specifically those who are unwed, because their affection detracts from what is available to the wife. From the perspective of the husband, other men close to his wife pose a threat to their social status because the ability to protect one’s property is part of masculinity, but also because a bastard son screws up the whole inheritance process. Unfortunately because the wife is viewed as an inferior being to the men, and because one woman who is dependent on her husband for sustenance is easy to control than an entire city of strangers, often enforcement of monogamy became a matter of punishing the wife rather than fending off the other men.
Today marriage is less about inheritance and livelihood, but it is still very much about social status and peer respect, and even couples who do not marry, but date within the monogamous framework, operate as though they were practicing for a marriage of the traditional sort. Jealousy is common and is sometimes interpreted as a sign of affection while being cheated on is a source of embarrassment. Society also expects that a monogamous couple in a Long Term Relationship will eventually begin to merge their lives, sharing finances and living spaces even before marriage becomes an explicit topic of discussion. Merely introducing someone as your significant other in any way means that friends and relatives will expect you to know that person’s whereabouts at all times, count you as two people when arranging carpools or parties, and communicate with that person as if they were you. And for many couples, these assumptions are not far off point.
To contrast, the history of polyamory is very different. To begin with, polyamory means many loves. Sometimes this is a fixed number of partners and sometimes it is fluid. I would like to focus on the types of polyamorous relationships that are open in the sense that there is not a predetermined number of partners that commit to each other exclusively. As an official socially acknowledged romantic structure, polyamory has only been observed in a small minority of cultures, notably those without the concept of paternity. Familial ties must necessarily pass through the mother, as does property transfer, and without the notion of paternity, the idea of sexual fidelity holds little value. As a corollary, economic security is also independent of sexual ties and so the choice to become romantically involved, or sexually involved with another human means little in terms of changes to one’s identity or social or economic status.
So polyamory exists inside a culture that has no social framework or historical basis on which to accurately acknowledge romantic partners, and it also lacks the moral imperative that monogamy holds. What this means for polyamorous people actively in polyamorous relationships is that, among other things, they lack the language to describe themselves or their partners. Members of a polyamorous relationship often find they have to explicitly undo the assumptions that others carry about their lives when discussing their partners. One particularly difficult one is the notion of availability. A polyamorous person in an open relationship is never officially unavailable, but declaring the presence of any romantic partner means that potential partners will keep their distance out of respect for the assumed ownership. Attempting to correct this assumption is full of all sorts of social pitfalls including replacing it with a different assumption that one is sexually loose or indiscriminate. It also means that there is no pre-existing commonly accepted template on which to build a relationship and that polyamorous people must negotiate their relationship structure and their boundaries on a case by case basis. Compared to monogamous relationships, polyamorous relationships must essentially build themselves from scratch both internally and externally with every new partner.
Much of the difference between polyamory and monogamy comes from the assumptions made by people, both inside the relationship and out, about the purpose of having a romantic relationship. Much of the rhetoric today praises true love and romance and assumes that the blind pursuit of these virtues will naturally lead to lifelong monogamy. In this paradigm marriage is a natural conclusion of the process of romance and monogamy is self enforcing. Polyamory builds itself on the idea that “true love” may be nurtured between more than one pair of people and as a consequence has no natural conclusion for the results of this love. While monogamists can use their social roadmap to plan their lives, trusting that when things fall apart there is already an infrastructure available to help them back on their feet, polyamorists must carry all the tools to plan and all the tools to recover from failure with them at every step of the way. The result of these differences is that the identity of a monogamist fluctuates with their relationship status while the identity of a polyamorist remains more or less constant.