1. Animals with horns and such do not have them at birth (they've got nubs at the most). They develop them later.
Giraffes and some goats are technically defined as being born with horns. They are not adult horns, certainly.
Suggesting that tieflings pop out of the womb with big, sharp horns is kinda silly.
Tieflings popping out of the womb, period, is kinda silly.
The fact that they have heavy bone ridges on their foreheads doesn't mean they're born with those ridges.
True enough. Brow ridges in neanderthals are thought to have significantly more than 5 years to develop. However, I can't see how horns going from nubs to ridiculous spikes or ram-features would be compatible with developing a skull shaped like that of a Tiefling. The weight distribution alone would alter the neck and skull shape. I can't see any rhyme or reason for exactly when those would show up anyway. In animals with horns they develop according to their evolutionary purpose. In the case of Tieflings, the horns are simply a skull deformity.
If the horns were developed in utero with the skull, brow, and spine and had persistent proportions it wouldn't be as much of a stretch for me - but then they'd be a major birthing hazard. The Tiefling models with much smaller horns shown make a lot more sense to me.
Frankly, 4th Edition Tieflings look more likely to have popped out of an egg than the Dragonborn to me - but that's probably too many episodes of Gargoyles talking there.
2. Tieflings are not all born to humans. Most are born to tieflings, whose bodies are designed to process tiefling children. They just automatically breed true with humans (as well as tieflings).
Hm, I was under the impression that the original humans that made the pacts were not themselves transformed, but rather their offspring bore the marks of the pact in their bloodline. I'm probably just getting my fluff confused between editions.
That appearance makes it much harder for me to export the Tiefling concept to world builds that didn't Giant Evil Tiefling Empire to explain away why they've been so widely integrated into the world as opposed to being exterminated on sight - whereas an earlier, more subdued design of Tieflings seem more widely viable.
3. If you can't see how a creature can go from being hornless to having massive horns, that's a failure of research, not the fault of the designers.
I can see how Quadrupeds with elongated skulls and very small brains can grow large horns from nubs over their development. I don't see how a humanoid skull and spine could support the same kind of development. Small-horn Tieflings I can accept far better than these exaggerated models in 4th Edition. They seem poorly modeled just to make the Tieflings seem more artificially scary and emotive.
I'd be more satisfied with a Tiefling that could actually wear a hat or a helm without needing extensive customization, buy a pair of pants, or sleep in a bed with a headboard like any other PC race. If any PC race made sense to put a tail on it was the Dragonborn, not the Tieflings.
The platypus would like a word with you about monotremes.
Yes, yes, the platypus and echidna - the extremely small and isolate exceptions to the genera rule about mammals - small, bird-looking critters.
Frankly, I'd think Dragonborn would have a lot more in common with, say, Dragons than the platypus but that's just me. Frankly, a lot of my impulses towards Dragonborn probably come from being introduced to the concept of Draconic Humanoids through Lizardmen, Yuan-Ti, and Draconians - all of which were described as "reptilian."
I guess I'd be OK with Dragonborn-as-mammals if the following are true:
1.) Dragonborn females nurse their young.
2.) Dragons are mammals that nurse their young.
Without both of those things in place Dragonborn seem too stretched from being Draconic on the one hand or Mammalian for me to be comfortable with their appearance and name.
- Marty Lund