I have a race of humanoids (soarfolk) who, as their name suggests, basically went from normal humans to humans with wings, hollow bones and feathers. Normal humans still exist, and interact with soarfolk, and I'm wondering what the humans should be careful about when dealing with their hollow-boned peers.

How hard would it be to break the bones? Would a human have to be careful about not pulling a soarfolk too hard, hold him too tightly, etc? Would slapping/punching cause severe damage?

  • $\begingroup$ According to close examination of pterasaur's fossil this prehistoric master of the air is a predator and was able to stay airborne by gliding using their large wings and hollowed bones. The records also hinted that they were very fragile when hatched from their eggs.They have to remain in the protection of the environment and the care from the adults and will start to wander out alone to search for food once they have matured and experienced to live on their own. Even reaching adulthood pterasaur can suffer from broken bone easily however there are no danger in the sky except their own kinds. $\endgroup$
    – user6760
    Apr 3, 2015 at 11:04
  • $\begingroup$ A big problem may be birth, which is quite a traumatising event for the baby. This is solved in the case of birds by using eggs, but here you can't do that. Good question though, welcome to the site! $\endgroup$ Apr 3, 2015 at 11:52
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    $\begingroup$ @skysurf3000 There is a condition known as precipitous birth in which a woman can have rapid progression and very minimal labor - the child almost "slides out." In such cases, hollow bones wouldn't be a detriment. Maybe the race split off from humans who had such a genetic predisposition? $\endgroup$ Apr 3, 2015 at 12:46
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    $\begingroup$ Not all mammals give birth to live young, platypus is a classic examples. Since your soarfolk have wings and feathers I'm sure your target audience won't mind a couple of soarfolks trying to lay some eggs at their leisure. Let me warn you human moms are going to be so jealous. $\endgroup$
    – user6760
    Apr 3, 2015 at 14:00
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    $\begingroup$ They called me Mr. Glass. $\endgroup$
    – Samuel
    Apr 3, 2015 at 15:48

3 Answers 3


I'd suggest reading up on osteoporosis. That will give you some good, factual reference points for how fragile human bones become as their density decreases and they become progressively "hollow".

That would also seem to imply some changes to the underlying musculature would be necessary/expected, as lower density bones would not be able to hold up to the same muscle density that you find on the average human, nor the same amount of stress when moving around and articulating joints.

How hard would it be to break the bones?

One soarfolk to another? Probably about comparable to how hard it is for one human to break another human's bones. Their bones break more easily on an objective scale, but when you factor in the reduced mass and reduced muscle density (so on average a soarfolk is both lighter and weaker than a human) the subjective impression of how much effort is needed to break a bone is probably about the same.

A human vs. a soarfolk? Comparatively easy (relative to breaking the bone of another human), as the human will have stronger bones and greater muscle mass. I'd imagine most any blow delivered at full force would have a good chance of breaking a bone.

Would a human have to be careful about not pulling a soarfolk too hard, hold him too tightly, etc?

Pulling I'd think would be okay except in extreme cases. The things likely to cause damage would be impact and torque. Holding/crushing might be an issue, but again I think only in extreme cases.

I'd think a soarfolk could generally shake hands with a human without fear, so long as the human didn't deliberately try to crush their hand. If the human did, however, they'd probably be able to crush a soarfolk hand (or ribcage) with effort.

Would slapping/punching cause severe damage?

Yes, punching especially. A human would be able to punch harder than a soarfolk, and would hit them with more mass than they'd generally be accustomed to. A human punching a soarfolk would probably be akin to a human with brass knuckles punching another human. Easily damaging, and potentially life-threatening in the case of, say, a strong blow to the face.

  • $\begingroup$ Of all places to hit, the head is the most likely to cause the one throwing the punch to take the damage rather than you. Even with hollow bones, the skull would, for all intents and purposes, be the same. Perhaps a better analogy would be brass knuckles to the ribs by a body builder, as opposed to getting punched in the ribs by an average man without brass knuckles for what concerns damage. $\endgroup$
    – Neil
    Apr 3, 2015 at 12:58
  • $\begingroup$ Since you are into diseases, you can also look up Osteogenesis imperfecta $\endgroup$ Apr 3, 2015 at 14:52
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    $\begingroup$ This would be the case if soarfolk just had hollow human bones. It should be noted though that avian bones aren't actually notably weaker than their mammal counterparts. Likely soarfolk bones would be easier to break deliberately, but accidental breakage wouldn't be much different that normal humans. $\endgroup$ Apr 3, 2015 at 17:31
  • $\begingroup$ @EldritchWarlord - I agree. Though depending upon how the hypothetical evolution played out, the bones may be like avian bones, hollow human bones, or something in-between. I'd think that over a long enough timespan they'd tend towards avian-like bones, assuming natural selection is in play (which it may or may not be, depending upon societal/technological factors). $\endgroup$
    – aroth
    Apr 4, 2015 at 2:43
  • $\begingroup$ The density of the bone is not the only crucial factors, remember the different arrangements of carbon atoms means either you get ashes or a diamond, a titanium alloy is many folds more durable and lighter than steel can current science is suggesting graphene also from carbon atoms but is better than all materials stated by myself or others. $\endgroup$
    – user6760
    Apr 4, 2015 at 6:39

The bone issue would only need referencing a line or two. The Author Brandon Sanderson speaks a lot about worldbuilding and only conveiging what is nessessary to the story. sort of like -"How can they get their weight off the ground." - "Hollow bones." Or as is the case with real bird bones, having them splinter when they break and a character witnesses it. Any surgeon would have a hard time dealing with splintered bones. It would depending on the technology, ability or magic, likely render a limb useless and may be better with amputation. - a crash could mean istant death.

Here is a bit of biology on hollow bones from Vet Approved PetMD

Avian Fractures

Just like humans, birds can also fracture (or break) bones and dislocate various joints. (A multiple fracture is when there is more than one broken bone, or a bone breaks in more than one place.) It is, however, not as easy to treat fractures in birds because many of the bird bones are filled with air, and have higher calcium content. When the calcium content in the bone is high, the bones become brittle and multiple fractures are more likely.


The veterinarian will take X-rays and perform blood tests to diagnose osteomyelitis.


Fractures may become complicated when the broken bone becomes infected. The most common bone infection is osteomyelitis. Osteomyelitis is a bacterial infection of the bone sheath which can spread to other bones. It is very painful and if the infection enters the blood, it may become fatal. Antibiotics are used to clear up the infection and speed the healing of the bone.


Fractured bones in birds heal faster than in humans or other animals. Usually a stiff splint, which totally immobilizes the broken bone, is the only treatment needed. During multiple (complicated) fractures, surgery may be needed to implant supports. This helps the bone function normally after it has healed. Physical therapy (physiotherapy) may be needed to loosen frozen and stiff joints, and maintain range of motion. The veterinarian will recommend various exercises to help your bird heal. The veterinarian will also prescribe medication to ease your bird’s pain while it recovers. Medication may be given orally, or through the feed or water. Observe the bird's recovery and return to the veterinarian if pain increases after a few days to rule out any infections in the broken bone.

I once wanted to write a novel about angels as real people with wings a long time ago - can't remember where i got it all but here goes. I did some research and they would have very large wings no matter the bone structure, look at a picture of a bird with its wings out, in general they are huge for the birds size. It would also depend on wether the wings where a seperate apendages making six limbs - no mammal has that. Or wether they were the arms or attatched to the arms like gliding of the flying squirel, all that would determine their arial capabilities, and their ability to fight and fly at the same time. Big wings make big targets - nets and long thin blades would be hard to focus on when moving at speed - if they are attatched to the arms they could not carry anyone or anything with any ease. They would get very cold dependent on feather layers or clothing that would add weight as facial skin may freeze at high speeds - they would need big lungs and a big heart to pump the blood around and breath at high altitudes. They may need eye protection or better focusing eyes - weather depending, they could be grounded and therefore vulnerable - mages that could cast weather spells could be of use. You can't keep many tactical secrets on a battlefield from a flying man - air control dominates, - possible use of bombs of some kind. - big predator birds could be used to cut them from the sky. Fire and heat can engulf and the best place to catch fire is just above the visible flame. These are all great things that the other humans should take into account. And after that you may find these people may as well be a different race entirely it may prove easier than explaining evolution. By our world standards evolution obviously takes a long time and i would guess is more developed out of nessesity. So the why wings I think is the more important question that you could really weave into a story.

An idea for the birthing could be that they are born smaller than normal people and the bones are not hollow when they are young, this develops over a few months/years to be hollow, the birthing ultimately is unlikely to need explaining although no animal does this at all.

That's me done. Peace!


I know someone that broke a hip by tripping/falling (just a normal fall, normal speed) because they had osteoporosis. I'm pretty sure getting into a fight for people with weaker bones would signify serious injury/death.

Take any number of examples of such cases in fiction (Samuel L. Jackson in unbreakable, Seth Green/Joker in Mass Effect etc...)

Interestingly enough, Author Alastair Reynolds has a sub-species of humans in his book Terminal World that have both hollow bones and wings (to fly) and addresses the issues of having weaker bones by having these humans be technologically more advanced and use some kind of nanobots to strengthen them.

Now without using necessarily some high-tech sci-fi fantasy (nanobots fall in that category for me) I guess you could maybe have some kind of medical or natural procedure to reinforce the bones, with any kind of lightweight hyper resistant material. You'd have to manage figuring out a way it wouldn't block the pores in the bones entirely. I thought of Kevlar but that can get just as heavy as having normal bones.

Having over developed muscles and tendons isn't necessarily a solution as you could end up with the problem of them snapping their own bones under the strain of their own muscles.


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