The Flurry Heart Phenomenon (headcanonS) · 7:37pm Dec 20th, 2016
Alicorns, as a rule, aren't born. Princess Twilight was born Twilight Sparkle the Unicorn. Princess Mi Amore Cadenza was born Cadance the Pegasus. The Royal Sisters... well, Celestia's being cryptic and Luna's keeping mum. But they agree that this has never happened before, so let's take it as a given that neither of them was a born Alicorn either. So where does Princess Flurry Heart fit in?
First, I feel I should reject some easy answers.
Perhaps Flurry Heart's birth tribe is a fluke, and this simply defies explanation? You already know I've rejected that, but I'll elucidate. This is a flippant answer, akin to saying, "The rule is AlicornS aren't born. We're allowed to have one." This explains nothing, and raises the question of why a second Alicorn couldn't be born. But I digress.
Maybe it's as simple as Princess Cadance being the mother? Mmmmmaybe, but this is also too simple. We would have to infer that the Royal Sisters never had children while they were Alicorns, or else we would see other natural-born Alicorns in the Equestrian population. And I don't know whether that's harder to believe of Princess Celestia, who has certainly lived among us a thousand years more than her sister, or Princess Luna, who is the only clear candidate for the ultimate ancestor of her sister's known nieces and nephews. (At a rough estimate, one descendant living at the time of Nightmare Moon's banishment would have 2^30, or one billion, descendants today if one assumes no large-Nth-cousin pairings. Rough as it is, the number is about 14 times a 25% saturation of Equestria's pony population, pretty much drowning out any corrections downward.)
Could Flurry Heart be not an Alicorn, but a Pegacorn--that is, a pony with the physical and magical characteristics of Pegasi and Unicorns, but not Earth Ponies? Without flatly saying "no," let's admit this would be even more extraordinary, as dual-tribe ponies have never been documented in the literature. Moreover, unless and until Princess Flurry Heart's Earth Pony magic is tested, it is impossible to rule this scenario in.
However, I believe I have found the answer. According to this statistic I just made up, there was a statistical anomaly in one aspect of the births in a six-week period that includes the birth of Princess Flurry Heart. Children born in this period are far more likely to have the same tribe as their mothers; at the peak, the probabilities were 74% for mixed-tribe couples, rather than 46%, and 99.1% for same-tribe couples instead of 95%. This strongly suggests that the tribe of the new Princess is not a fluke, but part of a phenomenon causing foals to inherit their dams' tribe rather than whatever factors normally contribute to the statistics. But what?
The length of the anomalous period gave me the necessary clue. Pony pregnancies usually range from 320 to 380 days, so a mean of 350 days and a range of 60. The six weeks, or 42 days, of the anomaly follow the same bell curve shape as the pregnancy distribution, so assuming pregnancies progress linearly, it's a simple ratio. 42 is 70% of 60, so the event occurred about 70% of the duration of the mean pregnancy prior to the mean birth, or 245 days before June 4, 1002.
That puts the event in early October 1001, and the implication is clearer than crystal. This phenomenon was the doing of Tirek.
We can draw several conclusions from this. Tribal differentiation must occur roughly four months into pregnancy, and must be a result of the fetus's magical signature. This is normally determined by the tribes of the parents and their ancestors, and while these factors already result in foal matching dam more than half the time, the increase is unmistakable.
But the phenomenon wasn't Tirek's systematic draining of pony magic. It was, rather, the sudden and complete restoration of our magic. Every expecting mother who was drained and re-infused was suddenly a magic-rich environment for her unborn child, and the mother's magic overwhelmed the baby's. And all this squares with the adult Princesses' accounts of Tirek's attempted takeover.
This, of course, raises some frightful questions not only for the children who will live their lives as a tribe not naturally their own, but also for parents and profiteers who might seek to rig a natural system we don't even fully understand. I humbly request to consult with you, should you consider suppressing my analysis.
Ha ha, OK, human author of pony now. I just wanna address one more detail: how the Cakes, both Earth Ponies, could have both Pegasus and Unicorn babies. Of course cartoon heredity runs on narrativium, not genetics, but where's the fun in that? Assuming consistency where it wasn't written gifts us with such things as Alicorn Granny Smith.
Now, I'm going to continue assuming the Alicorn tribe is not inherited. I'm also going to assume Cup was faithful to Carrot, because it keeps my sandbox smaller and we aren't forced to conclude otherwise, meanies. Moreover, I will guess tribe is determined by one pair of chromosomes. In short, Carrot has an E(arth pony) chromosome and a U(nicorn) chromosome, and Cup has E and P(egasus). (I think that's what they said, but even if I'm mistaken, the scenario's symmetric. Also, even if Cup's known Pegasus relative is only related by marriage, the gene ought to have come from somewhere.)
This isn't quite enough. No pairwise dominances of the tribal chromosomes allows these parents to have these foals without some tiebreaker. So I will make the... unfortunate assumption that the offspring's magical power is determined entirely by genetics, separate genes for each of the three usual tribes. But hey, this model's simple, and the point is to show it can work at all. If reality's messier, we can add messiness to the model.
So with that handwaved, we'll also need clearer notation. Define T(U) as a single tribal chromosome for Unicorns, and extend this to say T(EP) is Cup's genotype. Then we can define separate power chromosomes for each tribe: E(HL) denotes one chromosome for H(igh) Earth magic and one for L(ow) Earth magic (but only relatively speaking; the range of determinism might be narrow, and might not correspond with the adult pony's actual power level, yadda yadda simplify simplify). So I offer this:
Cup: T(EP) E(HL) P(LL) U(HH)
Carrot: T(EU) E(HL) P(HH) U(LL)
Pound: T(EP) E(LL) P(HL) U(HL)
Pumpkin: T(EU) E(LL) P(HL) U(HL)
There we go. Now while this system doesn't rule out two tribal phenotypes needing some further of tiebreaker, it's enough to show variety can be natural.
Counterpoint:
pinkie.mylittlefacewhen.com/media/f/rsz/mlfw8206_small.jpg
YEEEEAAAAAAAHHHHHH!
(Not to mention Princess Erroria as a potential pegacorn.)
4348363 Erroria can be disregarded as the product of Twilight's fevered imagination. She also saw some composite guards in her BBBFF song flashback. Moreover, background Alicorns in "real world" footage include Rarity, and this spawned another theory journal: https://www.fimfiction.net/blog/661526/genetic-latent-imprint-tribal-change-habitual-emergence-syndrome
But to your first counterpoint, is Bulk Biceps canonically an Earth Pony, in the show or the comics? I hadn't heard.
4349050
Well, I certainly hope Bulk Biceps is canonically half earth pony, because otherwise half of what canonically makes earth ponies special (their massive strength and stamina) is basically a "feel-good" pat on the head from the Actually Special pegasi and unicorns.
And with all respect to the linked theory (and your own), Pinkie Pie seems like a very plausible candidate for an earth pony unicorn.
4349432 In "Buckball Season," Pinkie Pie stage-whispers, "They know we're not Unicorns, right?" So she is documented as not being a Unicorn. I'm sure we could come up with scenarios where Unicorn!Pinkie would say that, but they would be about as contrived as "Mary Poppins is a Time Lady," or "the 2016 election was a playthrough of Frog Fractions 2."
4350182
Not that contrived, I think. She simply doesn't identify as unicorn, which makes sense if she grew up in such a culturally earth-pony environment.
In fact, if you want to talk about contrived scenarios ... earth pony powers are canonically linked to nature and living things, so if Pinkie Pie's entire family is pure Earth Pony, this directly implies that in Equestria, rocks are alive. It seems much more reasonable that they're all earth-unicorn hybrids who have a violent cultural rejection to considering themselves unicorn even in part, and so they farm their rocks (which even other ponies find strange) and blindly deny half of their heritage.
Note also that Trixie -- a unicorn -- is able to be hired on and help them farm. And that Rarity's cutie mark power (and origin story) is explicitly rock-related. Any theory asserting both that rocks are alive and that Earth Pony connections to nature are unique among the three tribes is going to have a hard time accounting for that.
Honestly, the more I think about this, the more convinced I am that my original joking suggestion was on to something.