Heard of p-shifting? Maybe not? As a pseudoscientific claim that circulates around the alterhuman communities (especially the otherkin and therian communities) on occasion, it rears its ugly and generally obnoxious head more than we'd like.
Regardless of your familiarity with the term, go give this a read.
P-shifting is a shortened name for "physical shifting". Physical shifting refers to physically changing the human body partially or wholly into a non-human being. Think something along the lines of werewolves shifting from human to wolf.
An older Tumblr post by Lupa puts it more succinctly and eloquently than I can, but I'll give it a go as well to drive home her points and my own. I suggest you go read her explanations as well. To put it simply:
It's physically impossible.
Promises of p-shifting have been repeatedly used to manipulate and hold power over vulnerable people.
Physically shifting directly breaks the laws of physics, through conservation of mass.
A 100 pound human shifting into a giant 500 pound wolf-beast would require that extra 400 pounds of mass to come from somewhere, and humans certainly aren't capable of pulling mass from the environment around us. The same goes for a 100 pound human shifting into a tiny 10 pound cat. 90 pounds of mass would have to go somewhere, and then would have to be pulled back into the shifter's body once they returned to human form. It's just not possible. End of story. Some p-shifters bypass the problem with changes in mass completely and instead claim no mass is gained or lost through shifting, but at the same time claim they can shift into creatures as large as 15 feet tall. Also, what about stomach contents? Maybe not a problem if you're shifting into a large animal, but if you're shifting into a small animal, that has to go somewhere, and considering it's not actually part of the human body, there's no reason you'd have control over it as well. Barf or rupture your digestive system it is, then.
P-shifting also breaks physics through conservation of energy.
Moving bones, muscles, tendons, organs, etc. cannot be done with a significant amount of energy. I've seen some "shifters" claim they just get hungry after shifting, but the energy required to shift an entire body instantaneously to a new form surpasses anything the human body can withstand or produce energetically. Not only that, but the shifting and stretching of bones, tendons, blood vessels, and organs would have to happen in perfect concert with each other, otherwise body parts would be irreparably damaged. A big round human brain that wasn't shifting at the same rate as a shifter's skull would at best be bruised and at worst be crushed. What happens with even minor brain bruising? Nausea, confusion, sensory problems...and in severe cases, seizures and/or coma. The same goes for other body parts as well, with bones breaking, muscles tearing, and blood vessels severing if not everything shifts perfectly. In all likelihood, this would kill the shifter.
Not everyone realizes it's impossible, and it's surprisingly easy to be taken advantage of if you don't understand why it's impossible and/or are desperate to learn to p-shift.
A good example is the various guides and handbooks on how to p-shift that have shown up over the years. Much like the questionable (and occasionally dangerous) fad diet guides sold in every corner of the internet imaginable, these p-shifting guides either offer inevitably disappointing results and excuses as to why you, the reader, simply must not be cut out for p-shifting, or they attempt to convince readers that the author alone holds the key to p-shifting, and that the reader can only unlock their abilities by following the author's instructions word-for-word (regardless of how dangerous or time consuming the instructions) or by offering the author something in return, whether that's money, favors, allegiance, etc.
Especially for younger or less wary folks, getting hooked on these guides can cause direct harm, through lost time and energy spent on trying to learn p-shifting, attempting dangerous practices, lost money on guides and shifting materials, and manipulative environments created through the power imbalance between the "teacher" who claims they hold the sole key to unlocking p-shifts and their desperate students.
On a perhaps less important note, it perpetuates pseudoscience. The way p-shifting is laid out by many of the authors, it's tough for folks without a background in science to sniff out as fake. Mistrust and misunderstanding of science is already a problem, and we certainly do not need more of it.
I'm genetically superior and/or have non-human genes that make me able to shift into a non-human animal.
Genetic mutations arise in humans constantly...that's a given, considering we're reproducing, evolving creatures. However, no recorded genetic mutation has arisen that has allowed anyone or anything to shift into a different species and then shift back.
There are rare, medically recognized mutations (e.g. hypertrichosis and sirenomelia) that on the surface appear to mimic animalistic traits, but these are in no way indications that physical shifting is possible. These mutations either result in defects beginning during fetal development (i.e. you're born with them), or manifest progressively over years...and they most certainly cannot be controlled by the carrier. Much like how we cannot control our eye color (which is genetic), we cannot control the expression of our other genetic traits at will. It's also worth noting many of these mutations reduce quality of life for their carriers, not increase it, like "genetically superior" would suggest.
Newborns are screened for a host of genetic abnormalities across North America, Europe, and Australia, and screening has been done since the 1960s, at least in the United States. Although specific genetic abnormalities are screened for, and I say this speaking as someone who isn't a medical doctor, I'd take a guess those screenings would pick up nonhuman genetic abnormalities, depending on how they manifested.
Finally, for p-shifters to know their shifting is caused specifically by a genetic abnormality, someone at some point would have had to have access to a genetic testing lab, know how to run the equipment, know how to interpret the results, and have the restraint to not tell anyone about it, even though exposing the p-shifting mechanism to the world would net you fame and (if you were smart about it) boatloads of fortune.
I have magical powers that give me the ability to shapeshift.
Practicing witches worth their salt will tell you that magic is energy-based. You can't manipulate matter directly, nor can you materialize anything - be it light, objects, or body parts. Even with exceptional quality tools and years of practice, physically manipulating your human body to shift into a non-human's, or even manifesting something small like a patch of fur is quite literally impossible, at least on the physical plane (the astral is another story, which isn't terribly relevant here). By manipulating your own energy, you can train your body to better sense your surroundings, move more like a non-human animal might, or become more in touch with natural processes internally and externally, but physically shifting into a non-human? Unfortunately no.
With practice, rituals and meditation can produce feelings of p-shifting, with strong phantom and mental shifts. Practicing methods like these can be excellent ways to temporarily alleviate species dysphoria. However, regardless of how real these shifts feel, they still do not physically manifest non-human body parts. If you're experiencing strong enough shifts that you're questioning whether you might actually be p-shifting, a great way to put the p-shift myth to bed is to film yourself while you're experiencing these strong shifts. An interesting aside; some have suggested people experiencing exceptionally strong phantom and mental shifts while visualizing (consciously or subconsciously) shifting into or possessing a non-human body may be one of the reasons some genuinely believe they can p-shift. It may feel incredibly real...but it's still not a physical shift.
My ancestors could shapeshift, and therefore I can as well.
Stories are stories. They may have been passed on from one generation to the next for a culturally significant reason, but stories offer no evidence that the tale ever actually occurred. The same goes for fairytales and legends. Stories of ancestors shifting into non-human creatures may be alluring, but no matter how many of these stories exist, they're still just stories, and offer no evidence that p-shifting is possible, especially considering we have proof it's impossible in the present day.
Attempts at proof:
Pictures of a messy/trashed room or natural area
Pictures taken from the internet
If someone sends you a picture as proof they p-shifted, use Google Image search to track down if it's been posted elsewhere
Save the picture and upload it to Google Images search by clicking on the little camera icon in the search bar
If it's been posted online before, it will show up in the search results
Manipulated or staged photos (i.e. Photoshopped, taken at weird angles to mimic weird body proportions, etc.)
Pictures of bite/claw marks, without evidence of what caused them
Excuses for lack of proof:
"I broke my camera while shifting so I don't have pictures/video"
"I don't own a camera"
"I don't record myself on principle"
"I don't want to show you my shifting because I have to be naked to shift, and I'm uncomfortable showing you that"
"I can't share evidence because the government will see and hunt me down"
"Giving you evidence goes against our pack's rules...sorry"
"I'm sorry you don't trust me enough to feel you need evidence"
Other emotional manipulation or threats
It all boils down to the fact that p-shifting claims simply don't add up.
Various rambling websites and social media accounts focusing on p-shifting methods exist across the internet, many with explicit calls for new members. Little to no vetting is conducted on new members, beyond requiring new members are "not human". If there was a concerted effort by p-shifters to hide themselves from the public, like a few have claimed, these websites and social media accounts would not exist. On these sites, information is given relatively freely in the form of step-by-step guides and pages of tips, even as the content creators beg prospective members not to reveal their shifting abilities to non-shifters. Given the lack of vetting, anyone could easily pose as a p-shifter to join a group or pack, and expose the p-shifters' abilities to the world. In other words, there's no way we would not know about p-shifting if it existed. Incidentally, we can at this point even figure out how long p-shifting could be kept quiet, if we estimate how many people would be involved in covering up its existence.
Descriptions of what it feels like to shift have popped up online, and few of them (even ones posted on the same site) describe the same shifting experience, methods, and shift speeds. Some p-shifters claim hard and fast rules, including a maximum shift duration before one becomes permanently shifted, sure ability or impossibility of being able to shift in one's sleep, etc. Certainly, if we were able to shift, there would likely be some individual variation, but not to the extent posited by various shifting accounts.
Considering the extreme interest in physical shifting in the otherkin and therian communities (a whopping 95% of the 420 respondents on this 2018 survey voted they'd like to be able to physically shift into their kintype), we'd likely be the first of the population to hear if someone had unlocked the key to p-shifting. Up to this point, p-shifters remain a fringe group, and greymuzzles and old fruits alike have publicly denounced the existence of p-shifting. At least one substantial monetary reward for proof that p-shifting exists has been offered with, to my knowledge, no claimers.
P-shifters have an absolute obsession with wolves. Yet, going on the genetic basis most of the p-shifters I've seen claim their shifts originate from, it should be much easier to shift into a closer human relative than a wolf. Sadly p-shifting into an ape isn't nearly as alluring as shifting into a monstrous werewolf of many a fairytale, and telling people you can turn into a bonobo doesn't catch the attention saying you can shift into a wolf does.