Pony Universe Design Thoughts: R63 + Gender Rarity

I've been contemplating actually daring to write for MLP for a while now, even though I originally started this account only for reading. But, recently, I've had some vague story ideas floating around, so maybe eventually I'll find the time and energy to put them into account.

This here is a little essay of mine that I've been contemplating, ever since reading a couple of fics, most prominently The Dawn of Dusk Shine, by . If I have similar thoughts along this vein in the future, I'll probably make this a series.

When designing the universe of your MLP fanfics, there's a lot of ways that you can tweak the universe for the sake of your story or just to convey your headcanon. Two of the more popular "themes" I've seen in my admittedly limited browsing of the site are R63 (short for "Rule 63") and Gender Rarity.

R63 is an internet meme that can be clarified quite easily as "gender flip". In an R63 story/verse, one or more characters have their genders altered; mares become stallions, and stallions become mares. This may be done selectively or enmasse; the most common version of the r63verse is one where all of the show's characters are the alternate gender to that of canon.

Gender Rarity is a more common and subtle form of 'verse tweaking. In essence, in a Gender Rarity verse, one gender is less common than the other. Iconically in MLP, the stallions are less common than the mares, and often get special treatment (positive or negative) as a result. The popularity of this verse is fairly high, and for a couple of reasons. Firstly, stallions have always been less common in the animated shows/toylines/comics for MLP, and even in Friendship is Magic, stallions tend to make up the minority of background ponies and spear carriers; making them rare in story thus meshes with what's seen on the screen. Secondly, in real life, horse and pony social structures consist of female groups with male hangers on, and this is the iconic image.

Now, either of these themes work well on their own, but bringing them together is a lot trickier. It can be done, but doing it in a good way is a little harder. A lot of writers tend to just work from the assumption of a Gender Rarity "coreverse" and then gender-flip everyone, but for me, this is not the best way to do so. Why? Because I cannot stop thinking about the "underlying mechanics" of the story, and pulling off a total gender-flip of the standard gender rarityverse requires some very substantial changes under the hood to be able to function.

You may be wondering what I'm talking about. Well, let's look at the mathematics of reproduction:
Let's start with the more common form of gender rarity; 7 mares to 3 stallions. Now, in a gender flip, that translates to 7 stallions to 3 mares.
We begin with a first generation of 300; that means there's a total of 90 breeding mares.
Let's assume each mare has 2 foals in her life; that means the second generation will be 180 ponies strong.
Of these one hundred eighty, 54 will be breeding mares, who go on to produce the third generation of 108 ponies. Which means that generation three has only 31 mares, who go on to produce a 4th generation of only 62 ponies.

So you see the problem; each generation gets smaller and smaller, because there's fewer viable females. In the real world, species with a higher ratio of males compensate by having females who produce dramatically larger numbers of offspring. With ponies, who produce one foal at a time and may only have 2 or 3 in their lives on average? Such a scenario leads to extinction.

This is why the "7 stallion to 3 mares' setup is one I personally don't approve of and wouldn't ever write; to make it believable, you'd need to create a verse where either the mares have dramatically larger broods of foals, or else where it's the stallions who get pregnant.

Now, I get that this is a matter of personal opinion, so please don't be offended; I can ignore this matter for some fics personally, and I don't see any problems with people writing them. I just find them a bit too hard on the suspension of disbelief to write them myself.