So I have a race of shapeshifters in my world, and in order to change shape or make adjustments to their body (grow wings, arms, tails etc.) They rearrange the atoms in their body, probably through magical means. Greater changes require more energy to move the atoms around, and can also be rather painful, meaning that a shapeshifter could potentially die if they exert themselves too much.

Would this method of shapeshifting have any serious effects on the health or inner workings of the species, especially considering that they nearly constantly change around the particles in their body?

Edit: If you don't spot any issues with it you can let me know as well!

  • $\begingroup$ As written, this question can only be answered if we assume fundamentally human physiology. Is that the case? If not, please explain (in substantial detail) the physiology of your shapeshifters. $\endgroup$
    – JBH
    Commented Jan 7, 2019 at 4:47
  • $\begingroup$ Why would it hurt? Pain receptors for noticing damage wont activate as there will be no damaged tissue after a change (unless the user is bruised after the change). Heat/cold receptors wont activate either unless the change creates a lot of heat but then they would sweat or die from acute overheating (hot enough to cause pain everywhere in your body is HOT). The only thing left is extreme pressure on pressure nerves during the transformation, but then you would also see damaged cells and bruising. So I dont think pain should be a part of this process. $\endgroup$
    – Demigan
    Commented Jan 7, 2019 at 15:26
  • $\begingroup$ Well ... there's always the problem of their last meal and where it goes. If they stay the same or increase in size, no problem. Ifthey change to something significantly smaller, say from human(ish) to ferret, it could be messy. $\endgroup$
    – pojo-guy
    Commented Jan 8, 2019 at 19:54

5 Answers 5


Yes, there are some serious issues with this over the long term because of the internal structures required to support the external ones.

First of all, the examples you've given all involve 'growing' a new appendage of some kind, meaning that you either;

1) Increase the mass of the individual quickly, or
2) Decrease the size of the individual proportionally to cover the mass going to the new appendage

In the first case, you've got to eat a lot, just to deliver the mass increase that you need. This means that the bulk of your abdominal organs are off limits during the change because they're actively delivering mass and energy for your new body's needs. In the second case, you've got to get the body to effectively denature itself proportionally and deliver raw organic materials to the areas where the new appendages are going to be.

Both of these are going to cause issues in the long term because of putting a massive peak load on the digestion tract or the imprecision of said denaturing respectively.

Of course, this doesn't cover off the other problem that you have, which is the need to support the new appendages with circulation, musculature, and skeletal changes. Wings are particularly problematic. If you're talking wings like the typical portrail of angels, then your wings need a massive musculature support through your back that those images traditionally gloss over. In birds, that musculature is the same as our pectoral muscles (hence why breast meat is so lean and large in poultry) because the wings are really evolved arms. Put the wings on the back however, and you've not only got to find a place for massive muscles back there, but the wings need to be very well affixed to the skeletal frame to support the weight of your changeling in flight, otherwise the wings will just snap off.

This may sound all easy in theory, but that kind of extra muscle support means you need much more blood, a bigger heart to pump it, a higher metabolism and the digestive system to support it, probably a unique channeling system that guarantees blood flow to our very expensive (energy wise) brains even when engaged in the massively costly exercise of flight, etc.

In short, you can't just add or remove appendages to increase the versatility of your changeling, you almost need to redesign the layout and capabilities of your internal organs from the ground up each time. That's time consuming and dangerous given the fact that these organs need to remain active during the transition. This is a little like trying to perform maintenance on the engine of a Boeing 747 at 2000m. At least 9 out of 10 aircraft engineers will tell you to land the plane first.

So too is it with shapeshifting. It's not the new appendages that will cause the problem, it's changing all the support infrastructure (internal organs, muscles, bones etc.) that are already in use to support the old body so that they can change the new.

  • 6
    $\begingroup$ "At least 9 out of 10" made me chuckle :) $\endgroup$
    – Tim B
    Commented Jan 7, 2019 at 11:41
  • 3
    $\begingroup$ @TimB - I see you are proud of your son, Tim B the second, rightful heir to the Worldbuilding kingdom. $\endgroup$
    – Battle
    Commented Jan 7, 2019 at 14:47
  • 1
    $\begingroup$ I love how people talk like they are specialist in shapeshifter, dayum. Great insights. $\endgroup$ Commented Jan 7, 2019 at 19:38

Multiple problems for any shape shifter:

Mass; Where is the additional mass coming from? It wouldn't be instant; they would have to eat and digest a whole lot as they grow whatever extra limbs. Even if they are physically capable of rearranging their physiology, any additional growths would take time, it would be awkward and inconvenient. Look at how inconvenient and time consuming pregnancies are. It would probably be painful to walk around with a half-grown limb too.

Weight; If the shapeshifter tries to make themselves bigger, they'll rapidly hit the cube square law. Bones will be strained, joints will wear. Even real life tall people can easily have bone problems. The shapeshifter will have to take steps to repair any strained musculoskeletal aspects.

Mobility; Even if you can grow an extra arm, that doesn't mean you can control it. Motor control comes from the brain, and the nerves. You can't just copy and paste - you'd have to edit your own brain patterns to make use of it. And anything editing brains is risky business.

Complexity; Which might be the biggest problem - this shapeshifter (presumably) isn't omniscient concerning biology. In order to redesign his own body, it has to understand how it's body works. You'd need a medical degree just to get started. Even the best doctor in the world wouldn't be able to rebuild a complex organ piecemeal, cell by cell.

Risk; Biology is delicate. Changing it is dangerous What happens if the shapeshifter makes a mistake? There's a reason most engineers try to deactivate a machine before modifying it, but the shapeshifter can't do that. He's running live, constantly; he has to make changes as he lives. What if he accidentally changes his chemistry too much or removes a vital bit of nerves as he shifts, and ends up catatonic or dead? He's got no safety or reassurance; his entire existence is in his own hands.

So overall, even if the shapeshifters could change their own biology to an unlimited degree, I don't think they'd be eager to try. A shapeshifter would maybe have one or two established and well-tested forms that they vary between as required - but trying to shapeshift freestyle would just be too difficult and risky.

Maybe a community of shapeshifters would get together and try to figure out the best shape. Still, i reckon these shapeshifters would have more medical issues than any other race combined; they are effectively amateurs that have been given admin access to a complex machine. There is no end of ways that they could mess things up while fiddling around.

All things considered, it might be easier for a shapeshifter to just... not use their powers. Live as a regular human, it's not so bad.

Realistically, what are these shapeshifters going to use their powers for? Humans are already pretty well designed for all activities humans do. Growing an extra limb or wings seems like a lot of trouble for not much gain, really. Unless they have a very specific application in mind, it'd be easiet just to stick as a human.

The most useful part of shapeshifting would be to strengthen and reinforce, rather than change. They'd be biologically immortal, if they could constantly update their cells to avoid aging.

  • 1
    $\begingroup$ "Where is the additional mass coming from?" We've covered that one already. Full disclosure: My own question. $\endgroup$
    – user
    Commented Jan 7, 2019 at 12:50
  • $\begingroup$ If there was a way for them to transfer learned shapes and improvements to existing functions to one another I'd say they would grow greatly in potential. Sort of like being able to pass on racial memory or skills. Whether through standard communication,a form of genetic ID storage for these capabilities or through a social interaction with another member of their species. $\endgroup$
    – Obelisk
    Commented Jan 14, 2019 at 10:16
  • $\begingroup$ Maybe born shapeshifters, such as therianthropes, have greater tissue mass compared to a regular human? This might solve the first problem (and possibly the second) and greatly reduce the risk of complications. And best of all, since their forms are predetermined by their genes, there is no risk of a mistake, possibly because it operates on a circadian clock. As for regular shapeshifters, what if the extra mass comes from fusing foreign atoms in the atmosphere to theirs? This would take practice but would yield promising results. $\endgroup$ Commented May 27, 2020 at 23:34

Rearranging all the atoms in a body to form a new body is probably way too complex and precise to be plausible. Even a Super Computer wouldn't be able to compute these changes, so this is probably the harder way of going about explaining shapeshifters.

An alternative might be to have the shapeshifted creature be in its complete form but hidden underneath a human form. For example a werewolf is desiccated/shrunken and hidden behind a human skin/façade/outerlayer. When the shapeshifted creature wants to turn back into its original form, it just pops out by rehydrating or something, shredding its costume. In this scenario the shapeshifted creature is not human, it just appears human sometimes.

As for why shapeshifters have a human form, maybe they are good costume makers, or maybe they can grow human skin and features when they choose too over several days. Either way we are only dealing with the outerlayer of being a human so it requires a lot less explaining to make work.

Explaining why a creature has a thin outer membrane that resembles a human is a lot easier to explain than a complete anatomy change.

However I understand that this breaks your idea of having shape changers die from expending too much energy, and doesn't make for any attractive hero shapeshifter characters.


It might be interesting to include shapeshifters whose abilities degrade with age or strain. Considering how complex the changes they undergo are, it is not infeasible that as they age, their shapeshifting ability gets less and less refined. It would be similar to human theories about aging, that accumulated damages/alterations to DNA over years of time causes old age. It could be that shapeshifters as they age are more likely to accumulate failed shifts, things like horns they can never quite get rid of or skin that is never exactly the right color. Or it could be that the more they use their abilities the more they risk accumulating damage, like straining a muscle and creating scar tissue. They might end up stuck with certain traits because of the strain and their shifts become less realistic and more horrifying.


If a shapeshifter is not just changing shape but also copying the internal workings then, and this process is causing pain. I think there would be the possibility for the shapeshifter to create larger than normal copies of the glades in the body that produce the chemicals that block pain or cause pleasure. Some of these chemicals could even be addictive or have other side effects.


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