Mewing and Facial Structure: A Critical Appraisal

About a month ago, I watched an entire, almost 2 hr-long video of a discussion on "evolutionary dentistry" and the effect of "oral posture" and jaw exercise on dental alignment and facial structure (https://www.youtube.com/watch?v=JYpPu-NrYSI). I'm not saying you shouldn't judge me negatively for this use of time - in fact, I recommend that you don't also use your time in this way- although the conversation was fairly engaging, and I have long been interested in evolutionary dentistry and facial morphology generally. The participants were one Bret Weinstein, perhaps the most 'lefty' member of the "Intellectual Dark Web", a former biology professor and a man I would describe as very grandiose, self-important, overconfident, articulate and largely thoughtful; and Mike Mew, another self-assured internet celebrity who has risen to prominence as a result of his promotion of a branch of medicine called "Orthotropics" and the set of exercises recommended by this fledgling science, known popularly as "mewing" (because Mew himself was the main populariser). Orthotropics seems to be intellectually founded upon an evolutionary-cum-physiological theory consisting of the following core propositions:

(1) The human jaw grows in response to chewing especially in early infancy (but also afterwards);

(2) A wider jaw means less tooth-crowding and typically ends up generating a correct bite;

(3) One's bite and facial structure are (also) affected by tongue and mouth posture, and may be nontrivially altered by changing one's posture even in adolescence or adulthood;

(4) The vast majority (?) of people could have entirely avoided malocclusion and related dental problems if they had been forced to chew more often in early life, and if they had maintained optimal oral posture throughout their life. (I translate this as follows: malocclusion may have a genetic underpinning similar to height - variation within populations is largely genetic (some people may be more susceptible to malocclusion than others) but the environment plays a very large role overall.)

There's also a more speculative outer belt to Orthotropics, or at least Mike Mew's personal version of it. Some of Mew's other proposals (evidenced in the interview) are as follows:

(5) Oral posture has a flow-on effect on general posture, and vice versa (the two form an influence circle);

(6) Chronic mouth-breathing has terrible effects on general health, including e.g. cognitive health, heart health and possibly even leading to acne;

(7) Maintaining optimal oral posture and frequently exercising one's jaw can also affect the shape of one's face more generally, making one's mid-face wider and flatter, and increasing the distance between the eyes;

(8) Traditional orthodontics would be (almost ?) completely unnecessary if everyone could maintain the optimal habits of oral posture from a young age. 

I shall now review each of these claims in turn.

Proposition (1) is supported mostly by evidence from archaeology comparing hunter-gatherer societies to agricultural societies, and by evidence from hunter-gatherer societies. There are two parts to the justification:  

(1.1) In hunter-gatherer societies, individuals are forced to exercise their jaw significantly more than in agricultural societies, and especially more than in modern industrial societies; 

(1.2) Hunter-gatherer peoples therefore tend to have wider and larger jaws, and overwhelmingly less malocclusion, than in these other populations. 

(1.1) breaks into two further sub-parts. 

(1.1.1) The 'norm' in hunter-gatherer societies, now and in the past, is that infants start chewing fibrous and otherwise chewy foods from a much earlier age than infants in modern societies. 

(1.1.2) Foods harvested by hunter-gatherers tend to be much chewier in general than most foods in the industrialised diet. 

The way Mew puts this idea in the interview with Weinstein is to say that we get our calories "too easily", whereas hunter-gatherers typically have to chew for a long time on raw, fibrous roots and undercooked or raw meats. Certainly, there are no ready-made "baby foods" for hunter-gatherers to feed their teething infants, and it seems intuitive that there would be less availability than we have of soft, high-calorie foods (soft breads, dairy products, sugary drinks and ice creams all result from complex industrial processes, and industrialised people probably also have better access to tender meat). 

In the interview, Mew claims at one point that searching for contemporary hunter-gatherers on Google Images will quickly demonstrate that the vast majority of hunter-gatherers have strong, wide jaws and good bites. I think that this is clearly wrong, as I tried it and saw plenty of images of people with small, narrow jaws and significant overbites. Consider, for example, the man in the first image on this website: https://www.crooked-compass.com/blog/hunter-gatherers-of-tanzania/. Try it for yourself. 

 I'm not saying this necessarily falsifies (1), because arguably the strongest evidence for (1) comes from archaeology: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0117301. There's also some palaeo-anthropologists and geneticists who think humans have undergone a kind of "self-domestication" in the last 10,000 years or so, leading to more neotenous faces (characterised by shorter face length, narrower faces, smaller skulls and bigger eyes) (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5646786/, https://www.jstor.org/stable/10.1086/677209?seq=1). This, if true, would likely be both genetic and environmental in causation and manifestation, so the implication for (1) is not straightforward. Regardless, it's important to bear in mind that, even if (1) is true, any jaw growth that is stimulated by chewing will be constrained by nutritional quality and health, as all growth is. If an infant is in a calorie-deficit, or lacks important nutrients, it seems unlikely that they will develop a powerful jaw, especially if they lack nutrients that are essential in bone-development. In a lot of his rhetoric, Mew seems to avoid this fact, or perhaps doesn't recognise it at all.

(2) is, I think, more or less conventional wisdom in dentistry and orthodontics generally. I think experts may disagree on the extent to which it is true - e.g. what "typically" actually means, statistically, which would be a complex problem - but I don't really think it's a position unique to Orthotropics. So that's a plus for Orthotropics. With this said, things can go wrong with teeth whether you have a narrow jaw or wide jaw. For example, the tooth roots can be disrupted via trauma, causing teeth to grow at wonky angles. I think I have this issue to some extent with one of my front two teeth (it is positioned slightly askew and sticks further forward than my other front tooth), possibly as a result of the fact that I lost my front two baby teeth violently when I was 7 (tripping and falling on a tree root).

(3) is the key to the explosion of Orthotropics on the internet. Again, I think that this is very close to conventional wisdom in orthodontics, except taken up a notch. Certainly, orthodontists all recognise that the growth of teeth is influenced by the various forces at work within the mouth, and that teeth respond, especially in early life, to physical feedback by moving and shifting. That's why braces are a thing! Similarly, all orthodontists agree with some of the stuff that Mew says about the benefits of nose-breathing and lip-sealing, e.g. that chronic mouth-breathers are much more prone to buck teeth.

The questionable part of this proposition is the second part: what I've described as the idea that adult facial structure - dental alignment, and palate and jaw width - "may be nontrivially altered by changing one's posture". To be clear, this is not a quote from Mew but an inference. Whilst I haven't quoted him, I feel that I actually have phrased the doctrine in a way that is actually quite understated, given what I've seen. (Obviously, this is a very vague and ill-defined proposition, with two weasel words in combination - "may" and "nontrivially" - but I don't think he himself has any kind of precise statistical model.) For example, he sometimes seems to say quite extreme things: if you watch 30 seconds of this video from the timestamp in the link (https://youtu.be/ZNocCJNicrc?t=211), you will see him describe his belief that one day while driving he managed to expand his "upper dental arch" after literally 45 minutes of exercise. Similarly, though he equivocates a little, he ends up endorsing to Bret Weinstein that his older teenage can be weaned off the retainer he is about to get from his orthodonist if he (the son) manages to implement the correct mewing techniques. (Mew also endorses that Weinstein's younger teenage son need not get braces at all if he can implement mewing). In general, the tenor and rhetoric of Mew's Youtube videos seems to encourage the idea that adults, too, can achieve significant results that will improve their quality of life. I've learned from here (https://www.nytimes.com/2020/08/20/magazine/teeth-mewing-incels.html) that the Mews' Orthotropics movement did start out focussed on children and that the push to claim that it could work for adults came largely from internet acolytes. But it certainly appears that Mike Mew has come to endorse the idea that his therapy is very much worth pursuing for adults. 

(4) is, arguably, just a corollary of (1) and (2), and similarly rests on evidence from hunter-gatherer societies and archaeological remains of pre-agricultural people. It also might be defended using evidence from other mammals, and at one point during the interview Mew or Weinstein (can't remember which) raises this idea. Again, we are forced to resort to vague language in describing it: what exactly does "the vast majority" mean, and how different would people's habits have to be? The translation I have made in brackets probably brings the idea closer to being falsifiable and helps specify the counterfactual in a more nuanced way (allowing for the Orthotropics theory to survive the existence of a society where everyone followed the correct practices for maximising jaw growth and yet a lot of people had underdeveloped jaws, because of, say, very poor nutrition). But even including that translation may err on the side of "steelmanning" too strongly, as Mew doesn't ever seem to talk about genetic variation in innate jaw size, which may indicate that he hasn't thought about this much. (He also never seems to explicitly reckon with the idea that some people are born with jaws so small - for genetic or other reasons (such as Foetal Alcohol Syndrome) - that it's likely impossible to avoid malocclusion, even under perfect conditions. Incidentally, lots of things can go wrong in the womb, affecting facial structure - for example, I have identified certain asymmetries in various parts of my own head that lead me to believe that the right side of my skull was squashed slightly either in the womb or during the process of birth. This, I believe, is extremely common.) Depending on how we do interpret this proposition, it's potentially undermined by the fact that lots of things can cause malocclusion, such as disease and (again) poor nutrition. And contra some speculations made in the interview, wild animals can definitely suffer malocclusion: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjRuYP07LDrAhVFbSsKHet1A24QFjAMegQIARAB&url=https%3A%2F%2Fbioone.org%2Fjournals%2FJournal-of-Wildlife-Diseases%2Fvolume-40%2Fissue-2%2F0090-3558-40.2.185%2FORAL-DISEASE-IN-FREE-LIVING-RED-SQUIRRELS-SCIURUS-VULGARIS-IN%2F10.7589%2F0090-3558-40.2.185.pdf&usg=AOvVaw1F41WeqE0vkn8nTrFyLBy5). So, certainly, there's a reasonable interpretation of this proposition under which it is wrong.

Now onto Mew's speculations.

(5) seems to me reasonable enough, but probably overstated (at least the way Mew states the "flow-on effect"). Although the main aspects of mewing are just tongue posture and lip sealing, another facet seems to be holding your head up straight, which is I think because it subtly engages one's masseter muscle (apparently good) and puts a little more pressure on one's front teeth. Holding your head up straight is certainly a way to mitigate bad posture, but, then again, there are some people - for example, my grandma - who probably always hold their head up in a normal way but succumb to kyphosis due to muscle weakness and whatever else. Posture is complicated.

(6) Not going to comment much on this because I don't really know. I do at least know that Mew is not the only person who thinks that chronic mouth-breathing is very bad for one's health generally. The acne hypothesis that he throws out to Weinstein is pretty odd - for what it's worth, my pet theory on acne is that it's made worse by constantly washing one's face with soaps, similar to how scalp oil production seems to respond somewhat to the frequency of shampooing - but at least he makes clear that it's just rank speculation.

(7) I'm very sceptical of this one. Again, I am more disposed to believe that activity in infancy may cause your adult face to look very different, but I'm very sceptical that adults can change their facial structure so dramatically (and, again, I'm not sure Mew is wholly consistent on this in any case).

(8) is very similar to (4) - almost a corollary. The reason this isn't a mere corollary of (4), however, is that I've left out the chewing-in-early-life part in the phrasing of (8). As I've made clear, Mew's rhetoric wavers, and at points during the conversation (and I think in some of his other videos), the importance of chewing in early infancy gets de-emphasised. This proposition is also significant for directly motivating a recurring theme of the discussion with Weinstein: the hypothesised influence of institutional and professional incentives on the poor reception of Orthotropics and Mike Mew among orthodonists. 

My personal experience with "mewing"

A month or two before I watched the video with Mew and Weinstein, I started changing my own oral posture according to what I understood the practice of "mewing" to be. I had first learned of "mewing" a long time before that, via a Youtube recommendation, and had also tried implementing the same practices at that time. I gave up quite early on the first time because the change in my tongue position was causing me to salivate a lot and it didn't seem to make a noticeable difference to my masseter engagement or the balance of pressures on my teeth. Even though I made exactly the same changes for my second attempt, and experienced the same initial problem with saliva production, I pushed through this and began to successfully engrain this new tongue position as a habit. After a while of doing this, I looked in the mirror at my bite one day and perceived that it looked straighter than I remember it being. Also, my front two teeth seemed slightly less forward-leaning than I remembered. I wasn't 100% sure - in fact, not even really sure at all (I try consciously to be a good Bayesian) - but it seemed evidence of a positive benefit. I also felt like my nose-breathing was possibly slightly better than usual.

But then I discovered that what I had been doing wasn't even "mewing"! In fact, it turned out that my natural oral posture was closer, if not already the "optimal" posture! (I'll get to what this says about the effect of "mewing" in a minute.) This confusion had come about because my initial resource was (I think) some video by Mew where he had described mewing as holding your tongue against "the roof of your mouth", and I figured that I was supposed to raise the tip of my tongue back and higher, behind the upper alveolar ridge and onto the slope at the beginning of the hard palate. In fact, the concept is more about holding your tongue high in your mouth generally. The tip can just sit anywhere behind the front teeth, ahead of or on the upper alveolar ridge (this is where the tip of my tongue was *naturally* positioned, and so it probably is for most people). I found this out from another Youtube video debunking "common myths", and this person's debunking was then confirmed by looking at another of Mike Mew's own videos in light of this understanding. After I realised my mistake, I also came across an old video where John Mew (Mike's dad and seemingly the progenitor of the movement) describes the ideal posture simply as the position of the tongue when one says "nnnnnnn". As far as I can tell, this is a 0-effort oral posture for me - I can't sense any movement of my tongue from its default position when I do utter this sound. So, if this is still Mewing orthodoxy, my oral posture was already optimal before I started doing the slightly more unnatural thing that I thought I was supposed to be doing.

Now, I'm not sure that Mike Mew (his son, and the main guru of the movement) would agree that the optimal posture can be encapsulated by this description. He seems to emphasise the idea that the "posterior third" of your tongue should also be against the rough of your mouth, which doesn't seem to be the case for me when I say "nnnnn". The problem with this idea is that I don't really have much control over the posterior third of my tongue. I can feel that my masseter muscles contract a little when I try to push my whole tongue up as high as I can in my mouth (I think this is "hard mewing") but, even supposing I tried to do this for many minutes or hours every day, it doesn't seem likely that this would cause a re-structuring of my face. (You could say my guess that it doesn't "seem likely" is not very good grounds for dismissing the idea, except that the effect on my masseter engagement is small, and for a small difference in masseter engagement to cause, over time, a change in bone structure significant enough to restructure my jaw would be pretty damn shocking to me!)

In summary, I think I already had close to optimal oral posture before I learned about mewing - and I certainly was always making an effort to keep my lips sealed and breathe through my nose (the most basic aspects of "mewing"). I think I probably even was swallowing the 'correct' way most of the time (i.e. relying only on the buccinator muscles) before I learned about "mewing". So whilst I guess that's good for me, it also suggests that mewing is essentially common-sense. More importantly, this further suggests that the practice can't really be that efficacious, given that there must be millions of people like me, with narrower-than-average palates and natural overbites, who have these conditions despite decent oral posture! To be fair, Mew does also recommend that people chew a lot of gum and regularly practise a tongue exercise called "tongue chewing" while doing so. But the main thing he emphasises is posture.

After I discovered that I had been confused, I decided, for obvious reasons, to put my tongue back to where it was before. So, in all, this whole experiment was a waste of time! 

 

Concluding Thoughts

 

A final word on Orthotropics. Some parts of the underlying theory behind Orthotropics seem to me reasonable, as I've made clear. However, Mew's statements often lack nuance, and he is not always fully consistent and precise. I think he is sometimes vague deliberately. In particular, he seems to employ a "Motte and Bailey"-style rhetorical strategy: he makes quite bold statements and promises - which lures in people hopeful that they can make themselves more beautiful and healthy - but at other times falls back on the idea that he's just promoting good old-fashioned "common-sense" (he actually says just this near the start of the conversation with Weinstein). Of course, Mew should not necessarily define this movement in general - that's why I made an effort to separate the core theoretical ideas from his personal speculations - but he is clearly the main driver. It's also worth bearing in mind that, just as traditional orthodontists are potentially financially incentivised to disparage Orthotropics and insult Mew, Mew is financially incentivised to over-promise on the benefits of "mewing" and disparage traditional orthodontics, because, as he says to Weinstein, this movement has become his entire career!

Personally, I don't think traditional orthodontics ought to go the way of the Dodo. Or at least, I certainly am not at all convinced. With that said, I do think there's intriguing evidence for the idea that aspects of our modern environment cause reduced jaw development, and that jaw growth can be stimulated by chewing, especially in infancy. I am sufficiently disposed to believe this that I have decided that if I have kids of my own, I will try to get them chewing things as early as possible (I am aware that raising children is very challenging and that for various reasons it can be hard to shape them as you might want, so it may be that I later renege on this.) But since I discovered that my personal tongue posture is pretty much 'correct' already (which also suggested to me that most people's tongue posture is probably correct), and when you recognise that most people already swallow in the way advocated by John and Mike Mew, mewing seems far less interesting. 

 

Overall, I suspect that, even if it keeps growing in popularity on the internet, mewing will probably not change the world. I suspect its ultimate impact on the world will be relatively neutral. It's possible Orthotropics will have a net positive effect on the world; I think this is most likely if the infantile-chewing part gains popular currency. But I believe it's equally possible it could have a negative effect on the world also, if those people who really need orthodontic treatment get suckered by Mike Mew's more radical claims. 

In short, the picture is nuanced, as many things are.