Pony Genetics and the Miracle of a Natural Alicorn Birth · 10:13pm Sep 14th, 2016
Pony genetics is a subject which has (arguably) been over-analysed to death following Mr Cake’s explanation in season 2 episode 13:
However this is maybe worth revisiting following the new development in season 6: the first natural-born alicorn in Equestria.
As has been widely discussed, Mr Cake’s explanation tells us that unicorns, pegasi and earth ponies can interbreed. And it appears that the genes which cause a foal to become a pegasus or unicorn are recessive, so an earth pony can carry a unicorn or pegasus gene, and pass it on to their foals, but they would only create a non-earth offspring if they receive a compatible non-earth gene from the other parent. This would also mean that two unicorn parents would always have a unicorn foal, and two pegasi will always beget pegasi. Just as two red-haired parents can have children with any hair colour they like—as long as it’s red. (Red hair among humans being similarly linked to a recessive gene). The precise mechanism has been discussed at length, and it would appear most likely that there are at least two genes at work here.
What about baby Flurry Heart? Her father—Shining Armor—is a unicorn. Her mother—Princess Cadance—is an alicorn, but was born a pegasus (as described in Twilight Sparkle and the Crystal Heart Spell). The outcome of a unicorn plus pegasus match seems to be the least well-understood combination, but as alicorn births are a once-in-over-a-thousand-years anomaly, evidently in nearly all cases there is some trigger (genetic or other) which causes a foal to develop as one or the other. Presumably if a foetus starts to develop a horn, then something blocks the growth of wings (and vice-versa).
But this didn’t happen to Flurry Heart. It could be, due to some other genetic mutation, her body was immune to the don’t-be-a-unicorn or don’t-be-a-pegasus signals, so she developed as both. In a similar way to how a human with androgen insensitivity syndrome develops as a girl, despite possessing the Y chromosome which would usually make her a boy, as her body is insensitive to male hormones.
Another possibility is that Flurry Heart is a chimara, and possesses the DNA of two individuals, as a pegasus and a unicorn embryo somehow fused together in her mother’s womb.
But we should also consider what happened to her mother. Cadance, like Twilight, was elevated to an alicorn princess after achieving a great act of magic. This would suggest that many (maybe every) pony has the potential to become an alicorn, and the genes discussed above are just triggers. So Twilight was subject to a powerful magic which caused some stem cells in her body to forget that they were part of a unicorn, and (with remarkable speed) develop into wings. Cadance acquired her unicorn horn through a similar process.
[As an aside, we could ask quite what Celestia thought she was doing performing such radical biotechnology experiments on her students, apparently without informed consent.]
Such a process would not change a pony’s genetics—so how did Cadance pass on alicornhood to her daughter? We should remember that a mother can pass on more than her genes to her offspring, and a possibility is that whatever bit of magic it was that caused Cadence to turn into an alicorn, it stayed in her bloodstream, and like a bit of viral DNA, or chemical signal, was passed to the unborn Flurry Heart and had exactly the same effect on her body.
It is not clear if this would happen to any alicorn-born, or only to a foal with compatible genes. One further question is why all the alicorns we have seen so far have been female. It is possible that alicorns need two X chromosomes in order to receive a pegasus gene from one parent, and a unicorn gene from another.
Maybe the biggest question is why are natural alicorn births so rare? We can imagine that being an all-powerful winged unicorn would come with enhanced reproductive success, and so should be favoured by natural selection. But the circumstances surrounding Flurry Heart’s arrival answer this. Remember, she very nearly destroyed the Crystal Empire through her uncontrolled magic. It would seem that alicorn foals are not only naturally inclined to remove themselves from the genepool, but can obliterate the genepool for miles around. So we would expect, by natural selection, for ponies to evolve very effective ways to avoid natural alicorn births.
The Price equation? teh chance of a trait passing on is a function of that trait and its passing method surviving?
I thought we all agreed the Cakes just visited the sperm bank because Carrot had bad swimmers, and he was too embarrassed to admit it?
Celestia and Luna are true superpredators.
To avoid complications to the gene pool arising from individuals who can breed for centuries, it may be that alicorns are sterile. Ancient populations in which alicorns were not sterile died out due to crippling deformities, mental illness, infertility, etc.
Well, she tried getting consent with Sunset Shimmer, and we all know how that went.
In any case, I do like the idea of alicornizing hormone or what have you leaking into Flurry Heart in vitro. And the reason why we've seen so few alicorn births. I can only imagine how Celestia and Luna's parents dealt with it, assuming they didn't ascend.
4210102 Alpha predators, of course. National Geographic did a show on them.
* * *
Four princesses sequestered in the most secure room of the Crystal Empire looked over the tattered pile of paper, which had been reviewed and summarized and analyzed until only one conclusion could be reached.
"Most certainly, I should not test this theory," said Princess Luna. "If perchance there is the smallest fraction of Nightmare Moon still within my body, it may take the opportunity of foaling to transfer to a new host, causing an alicorn foal with unbridled power and destructiveness."
The castle shuddered to a magical impact somewhere far above, and a faint trail of dust drifted down to the floor of their bunker, along with the distant giggle of a small foal.
"How in Equestria would we be able to tell the difference?" said Princess Celestia. "Likewise, my advanced age makes me ineligible for testing the theory."
"No matter how many colts from the Royal Guard Academy you've 'tried out' last month," murmured Luna.
"Which leaves us only one untested princess to test." Three set of alicorn eyes turned to Twilight Sparkle, who stared back in disbelief.
"Me? But--"
"I shall go make arrangements with the duty schedule to free Flash Sentry for this task," said Princess Celestia, vanishing in teleportation spell.
"I shall arrange the stars and the moon for an appropriately romantic evening," said Luna, also vanishing afterward.
"I'll go spike the chocolate and the wine with fertility hormones," said Cadence, hopping up from her chair in a squeal of joy. "This is going to be so much fun!"
"But--" Twilight paused as Cadence likewise vanished in a burst of magic. "But he already has a coltfriend."
Here's my sciencey, hand-wavey take:
Magic is a parallel to genetics and general biology, not a direct cause or byproduct. It has its own set of inheritance rules and works on a wholly different timescale (ie cutie marks suddenly appearing, alicorn status being attained, anything involving Pinkie, etc). As I suggested on one of TheMaskedFerret's blog posts in the wake of the CMC's cutie marks appearing, this is just another realm of study for ponies, something that they only have a rudimentary knowledge of.
I think this jived nicely with Twilight's presentation in Cutie Remarked about the study of linked cutie marks. Maybe it's not unheard of, but not fully understood.
What we (and possibly they) really need is the Punnett of Pony Magic
Nice.
People insisting that Mrs. Cake must have been unfaithful is a very minor pet peeve of mine. The possibilities in genetics more than allows for the twins to be the natural children of her husband, even before you bring in whatever nonsense magical biology might add.
4210346
This belongs in Never the Final Word I think
That's ... tragic.
Like, it's literally the plot of a tragedy-story.
Two proud parents. A newborn foal-alicorn, with great expectations. Everypony celebrating. Surely, any hardships their community faces will come to an end through the birth of this child! They must tell everypony the good news, they must tell the world!
And then it ends in an unexplained explosion, vulcanic eruption, instant-freeze blizzard, spontanous meteor-strike, type 10 earthquake, or bizarre magical effect.
Outsch.
.......Probability demands there exist some alternate Equestria where alicorn-births are known, and feared. "If an alicorn-foal is born, your kingdom will surely fall." Alicorns are a bad omen, they bring the apocalypse!
So, cue an alternate universe where Celestia and Luna's ascention brough with it fear rather than awe.
. . . Wait, what were we talking about again?
4210102
You would certainly expect fertility to drop off after the first few thousand years.
4210249
Did you mean in vivo? I guess in vitro may also work for crystal ponies
4210346
I hope Flash enjoys unexpected bonus of being relieved from sentry duties.
4210527
I can agree with that. It came across to me as a simple comment on how inheritance can work out in slightly counter-intuitive ways.
4210731
The billion-year of evolution by natural selection is full of such tragedies.
4211315
Oh. Right. Whoops. I studied physics, not biology. I guess it shows.
4211315 The theory I've had for a while is that it could be chromosome based, working similar to how biological sex does.
Of course, it's been a couple decades since I've had any biology, so I may be making this more complicated than it is needs to be.
4210346 4210617
Are all y'all trying to keep me from working on anything but NTFW?
I'm amused, anyhow. I'll put it in the queue (and wait for something else to come along and pair up with it). Although at this rate maybe Georg oughta consider starting his own sequelfic collection ...
4211968 NTFW for blog posts might be a little much. Besides, why would I start up my own when I can have you do all the work
4211968
4211972
Yea but I mean NTFW for a story-blurb in a blog post still seems fitting also yes Horizon I am trying to do just that.
That way your weird time loop story can NEVER FINISH BMWAHAHAHAHA
4211972
There's precedent! And a blog commentfic is more likely to have been missed by readers than a story commentfic, so even though they're kind of borderline I'll definitely throw them in if they amuse me enough.
All but one Alicorn we've seen was by-ascension, so that they are all female might be coincidence. Big Mac DID become an alicorn in the dreamworld, so it might be possible.
I doubt it's genetic. Mostly likely it's magic getting passed to the foal. It is highly likely that Celestia and Luna never had children, though I suppose it could have happened before the Nightmare Moon fiasco. After that, I doubt Celestia would have wanted to, and Luna was, of course, imprisoned. Before... well it would partly depend on when they became aware of their longevity, I suppose. I've yet to be fully convinced that their longevity is solely due to being alicorns. My personal pet theory is that it's related to being linked to the Elements of Harmony, which they aren't anymore.
Regardless, if they never had children, then there probably simply hasn't been any chance for an alicorn birth in their living memory.
Heh.
My theory is still that Flurry Heart is a baby changeling. Probably how the queens reproduce, where the kid takes the form of the mother's species until old enough to control their magic. Normally a great way to blend in. Not so much when mother is an alicorn.
Your forgetting that an alicorn is not a pegasus/unicorn hybrid. It's a tribred between all 3 subspecies of pony. It may be so rare for them to be birthed simply because a family has to have genes strong enough from all 3 types of pony combined with some sort of magical catalyst. Or perhaps alicorns can only be birthed when one parent already is one. Luna and Celestia have no cannon children or relatives. Blueblood is a cannon descendant of princess platinum not the royal sisters. In this case they would never have seen or heard of an Alicorn birth. Very simply explained.