1141420 let me say this first: alicorns are not immortal of divine, just insanely powerful.

Twilight. THIS WILL BE FUN!

Twilight has SOME alicorn ancestry. when she was transformed, Tia simply unlocked a repressed and very diluted gene sequence. of course, using magic, she was able to open the sequence, and due to being in a space outside the laws of physics, she was able to create the excess matter needed for wings.

1141438
Okay, so if I'm reading this right:

- Alicorn-ism is recessive
- Twilight is/was an alicorn 'carrier'
- For the transformation, 'Tia flipped those genes from 'off' to 'on'

Theory questions:
- Could the same thing happen to Shining Armor?
- What about Cadence? For example, is Cadence or Celestia more representative of the alicorn race?
- If alicorns are 'just' insanely powerful, is Celestia a special case?
- Assuming Twilight is more powerful now than she was before, compare Twilight's new power level to Celestia's.
- I don't think you explicitly explained changeling horns. How closely are changelings related to alicorns?

1142178 yes, the same could happen to shining armor

Cadence is a young member of the species, under 1000.

Yes, Tia is a special case, but through training and study, not natural ability.

more powerful than Cadence, less than Tia.

Changeling's horns are convergent evolution, the fact is that they're genetically closer to earth ponies.

1142315
Hehehehehe... We are so, so technically wildly off-topic for this forum

Now, as I recall, we are confirmed on-screen to have unicorns and pegasii interbreeding with earth ponies, and alicorns implied (albeit indirectly) on-screen to be interbreeding with unicorns. If we fill in a decidedly off-screen detail about Cadence, we'd presumably have all four interbreeding no problem; that would contradict a locally assumed detail about Cadence, but I'm going to assume they can interbreed anyways (because that's what I would have done without Twilicorn and this detail about Cadence, too). Because of the way these four are interbreeding, some forms have to be dominant over others. What's the dominant/recessive stack look like? (For example, is pegasii dominant to unicorn?)

What about other equinoid offshot species you mentioned, can they interbreed as freely? If so, how do they fit in the dominance stack?

1144427 Earth ponies are dominant, but only by a small amount. alicorns are more common than is usually guessed, but are still rare. Pegasi, thestrals, and unicorns are about even.

donkeys, ponies, and zebras can interbreed to produce mules and zonies and ze-donks, but these tend to be sterile. changelings are too far removed, and horses are pureblood-crazy. flutterponies are supposedly extinct. sea ponies can interbreed with normal pony species, but hybrids aren't noticeable. Ditzy, for example, is a half sea pony, resulting in a special waterproof coat of fur and a higher tolerance to cold water.

1144516
That's good headcanon, but unfortunately does not answer my question, which was about genetics. We don't have, for example, cases of partial wings (though we may have wings which can't be used for flying), or partial unicorn-ism (unless you count Pinkie Pie. Maybe). And it's generally unsafe for a pegasi/pegasi pairing to give birth to a foal lacking the pegasi cloudwalking attribute -- which may happen in your headcanon, and we just haven't heard of it, but that's not the point. I think last I thought on this I cranked alicorns to most recessive and I'd have to dig my notes out much beyond that.

The sea-pony mixed attribute interbreeding is an interesting idea, though. Perhaps that explains more of alicorns than we know.