Ive noticed a larger than usual influx of people venturing onto the main chat asking about werewolf spells and how to shapeshift into a werewolf. When we (general members on the forum) calmly explain why this cannot be done as it defies the laws of physics and this nice little thing called science, often the person asking returns with caps yelling at how we are all stupid, sometimes we are cussed at, other times they type incoherently and just leave. During a discussion elsewhere, someone asked me to explain in scientific terms why becoming a werewolf and shapeshifting is not possible, and I decided to add this response here to the forums, as I felt it could serve as some kind of learning experience.
Now, let me reiterate my whole point here: I am coming from a science-based background. I am looking at Physical Shifting under the lens of science. I say "science" to mean in-general instead of sitting here and naming all of the various branches within science one would have to draw their information from in order to discuss this. Science may not understand everything (since this is often the excuse seen in chat), but one thing is does know is that the human body cannot physically change its shape from that of a human being to that of an entire different species. One would have to have the genetic material of said animal somewhere in their body and be born with said materials; else the human body would reject the foreign materials (human bodies to this day still reject transplant organs and donor blood from other human beings). Since humans cannot breed with anything that isnt a human being (genetic materials are incompatible with one another and will result in simple cellular death), no one can claim to be born a werewolf, or part wolf, because it is not possible.
First off, the human body is not capable of producing matter out of thin air. In order to become a werewolf, one would have to somehow materialize matter in and on the body to create a tail, muzzle, ears, and other parts humans do not have already. Even fangs require materials that the human body does not have. This is not possible, and here is why. According to the Mass-Energy Equivalence, to create a kilogram (2.2lb) of matter out of nowhere, you need to somehow manipulate a massive amount of energy equivalent to 21.5 Megatons of TNT exploding at once (~90,000 TJ). This is greater than the amount of energy released by the Castle Bravo nuclear test (15MT/82,760TJ). There's just absolutely no way you can store that much energy in your body or to draw it from thin air, much less manipulating the said energy to synthesize matter. All of it, in current laws of physics, is quite absurd. The human body, no matter how much one wants to believe, cannot create or handle the equivalent of a nuclear bomb being suddenly detonated within its body.
If one was to go with the idea that the human body would simply reorganizing our already existing materials into new parts, the issue is how? How is a human being going to change their selves into lets say a Grizzly bear? The average female human height in the United States (where I am located, as height differs per location) is 5'4.6, while the average Grizzly bear, is 6'5''. The average female weight is only 165lbs, while the average Grizzly bear weight is 400-790lbs. Now, when one claims to Physically Shift, this is an instant occurrence, not one that takes years to complete. From what I have been told via various sites and people who like to talk about this constantly in the public chatter, this is something that takes no more than an hour to achieve, and even then, that is pushing the maximum time limit. How, in only an hours time, is the human body going to reconstruct itself into a bear? Human hands and bear hands are not the same in their skeletal or muscle structure. The claim of "our fingers would become bear fingers" simply cannot apply. Bear's finger bones and joints are harder/thicker/stronger than our fingers. Somehow, in an hour, our bones would have to not only grow in size, they would also have to grow in their make-up as well, for the human's skeletal structure is too weak to support the size and weight of pure bear muscle if our bones could magically stretch to size (humans who support 400+lbs can barely move their bodies as is). Our bones would have to become reinforced within an hour. Somehow, we also would have to grow bear claws, and human nails do not grown instantly. If they did grow instantly into bear claws, where would they gather the minerals and keratin required to create them from the body? One would need an extra supply of necessary materials somewhere in the body on stand-by that wasn't needed for anything else, which I will explain in a second as to how this also cannot happen.
Now, on top of this, the issue of creating parts out of thin air still applies. Already existing human hands becoming bear hands is already one stretch, but bears do have little tails (nubs), and any animal with a long tail has bones within that tail. Then, there is the issue of a bear's muzzle. The human face has what bones it has. There are not "joints or "spaces" (minus the sinuses of the skull, or the cranial sutures that, you know, hold our brain where it is) in the face for our mouth and noses to just magically stretch into a bear's face. We would have to create new skeletal structures to create a working muzzle; there is no other way to do this, and doing so would require materializing matter which I have already explained cannot be done by the human body.
Skeletal structure aside, what about simple things like fur? The average human hair growth rate is only 0.5 inches a month. How would the human body just speed up growth of hair to a full coat of fur in only an hour, covering the entire body? Even genetic disorders that cause excessive hair growths (such as hypertrichosis, which is EXTREMELY rare) are disorders one has to be born with (resulting in hair existing at birth) or later development that still takes the body years to come full circle. The issue I have is hair is made up of keratin, which not only makes up our nails, but also the outer/first layer of human skin, and keratin requires amino acids, proteins, and enzymes the rest of the body requires to keep cellular growth in working order. If the human body could suddenly grow hair at such an astounding rate, the materials within the body that are being used would have to be pulled from other sources in the body at such an alarming rate, cellular growth would be stopped due to the sudden draining of resources necessary, and the body could force its own cells to undergo autophagy at such a high rate, it would kill the cells and the human body itself. In normal circumstances, autophagy is something that occurs every day when cells die off and new cells are formed. To suddenly take away the nutrients and resources necessary to create new cells, the body's organs and processes would simply shut down and die. This is kind of a problem, because we would be dead.
Last but not least, organ growth. The human heart is almost the size of a bears (smaller of course), but the human heart is not able to suddenly pump more blood than usual without taking on a high amount of stress. Human lungs would collapse under such weight, and if they didn't, they could not pump enough oxygen into the bloodstream that is required for basic functioning. If the brain suffocates, it dies, and guess what that means? The organs within the body would have to force themselves to grow in order to avoid this problem. This does occur in human beings, but not overnight, not by non-harmful natural circumstances, and definitely not in an hour. If the organs could grow at such an alarming rate, coming down from the shift, our organs would be too big for our own bodily structure, and could end up deteriorating simply from being crushed in on themselves. Bodily organs can shrink, sure enough, but not within an hour after suddenly enlarging as fast as they would be required. The overall stress on the body could literally cause the heart to explode. The overall stress of shifting in general could kill someone.
For those who I know will respond that magic can do it needs to go do more studying, research, and develop a basic understanding of how magic works.