In fanfiction, there are certain AUs that exist in every fandom big enough to have them. I don't mean coffee shop AUs, although those are everywhere. I mean universes parallel but alternate to this one and the original canon. Like, for example, the infamous Alpha/Beta/Omega AU. (If you don't know what that is, you probably don't want to look it up.)
My personal favorite AUs are the last ones to arrive in any fandom: Sentinel AUs and BDSM AUs. One day I'll probably talk about Sentinel AUs, but today I'm talking about BDSM AUs. (If you don't know what BDSM is, you probably don't want to look it up. Just skip this post.) I'm not talking about sex, mind; there are plenty of sources on how kinky sex works, and I'm not one of them. I want to talk about the particular changes that must happen in human society and history in order for BDSM AUs to work, because they are fascinating.
In BDSM AUs, in addition to being divided by male and female, humans are divided into Doms and Subs. (Don't ask why there are capital letters for these things. Everything takes on added significance in speculative fiction.) While male/female/other is defined as "gender", Dom/Sub identity is definedd as "dynamic". There are also occasionally switches mentioned, although it's unclear how that works (which I'll probably tackle in another blog post. Maybe for a Meta Monday post). Relationships are almost always between a Dom and a Sub, although occasionally there are mentions of "homodynamic" relationship.
Which leads my mind to a very interesting train of thought.
If heterodynamic relationships are the norm, then are heterosexual relationships still the norm as well? It never seems that this is the case, because, like most fanfiction in general and kinky fanfiction in specific, BDSM AUs are overwhelmingly gay. And there is never a mention that two men don't work together, in any form; so in these AUs pairings of any gender appear to be normal as long as the dynamics line up right.
Which leads to a whole world of possible sociological and historical implications. If homosexual relationships are normal so long as they are heterodynamic, that changes the cultural narrative. Unlike A/B/O fics (seriously, don't look it up), the dominant relationship in BDSM AUs do not carry an automatic assurance of fertility. But in early days when people died at staggering rates, there must have been a cultural narrative that demanded fertility.
So let's suppose that in medieval times and middle ages there was a demand for heterosexual relationships. Did they accept that female Doms and male Subs exist? Were homosexual relationships still accepted, if it was a younger son in a heterodynamic relationship?
My theory is that in those early times, a first child of any gender was expected to be a Dominant. Instead of primogeniture referring solely to men, it would refer to the first child, and that child had to be a Dominant and had to marry a Submissive of the opposite sex to carry on the family line. To do otherwise was unacceptable; but beyond that first child it was up in the air.
Alternatively, primogeniture referred to the firstborn Dominant, who was expected to marry a Submissive of the opposite sex. The problem with this is that it's unclear in these AUs how early you can tell a child's dynamic, so parents might be uncertain if they had an heir for up until puberty started. So personally I think the first is more likely.
Was there ever a narrative that said men should be Doms and women should be Subs? It doesn't look like such a narrative carried into the worlds where these stories are told; as I said, these fics are overwhelmingly gay, so there's always at least one male Sub. I don't think such a narrative would hold water, because rather than men, Doms are expected to hold all the power in these worlds. There are even mentions that your dynamic shows on your driver's license, like your sex does in the real world.
So we have a world where instead of male/female being the main narrative, it's Dom/Sub, and sex is a relatively minor piece of someone's identity, used only to determine whether a marriage is fertile, not whether it's valid. In such a world there might have been a dozen female presidents of the United States, but there would never be a Submissive president. Female Doms would get the same representation as male Doms, but Subs of all genders would get short shrift. They'd never be the main character, they'd suffer all the negative stereotypes, they'd be the comic relief or love interest. And instead of homosexual relationships being the big controversy, it would be homodynamic.
Maybe I'm the only one who finds these universes to warrant deep thought. But honestly, it's fascinating what one additional identifier can do to a universe.