PDF Summary:Jaws, by Sandra Kahn and Paul R. Ehrlich

Jaws discusses how our modern lifestyle has created a hidden epidemic of jaw deformities, leading to widespread health problems. Orthodontist Sandra Kahn and ecologist Paul R. Ehrlich say that a decrease in average jaw size is contributing to health issues such as sleep apnea, cardiovascular diseases, ADHD, and cognitive decline. The book calls on doctors and scientists to recognize that this is a serious issue and to give it the attention it deserves.

This guide will start by explaining the evolutionary background of our jaws and the harmful impact that modern lifestyles have on oral health. From there, we’ll discuss some of the harmful effects that come from having an underdeveloped or deformed jaw. Finally, we’ll explore some options to prevent or correct these jaw deformities.

Our commentary will provide additional evidence both for and against the authors’ ideas. We’ll also discuss some other factors that contribute to modern-day jaw problems. Finally, we’ll provide some tools and actionable advice to help you prevent or correct these issues.

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• A survey from the late 1990s showed that well over half of the US population needed some form of orthodontic treatment (such as braces, tooth extractions, or oral surgery).
• A study from 2007 found that almost two-thirds of people in Sweden needed orthodontic treatments.
• In a lecture at the Ancestral Health Symposium at Harvard University, one orthodontist said that 95% of people on Earth have misaligned teeth, with around 30% having misalignments severe enough to justify orthodontic treatments.

Clearly, this is not a rare or isolated problem: If the Harvard researcher is correct, it’s affecting billions of people today. In short, people all around the world are suffering from underdeveloped jaws, especially in developed countries where soft, highly processed food is the norm.

Further Statistics on Misaligned Teeth

The World Health Organization (WHO) considers misaligned teeth and jaws (malocclusion) one of the most significant oral health issues affecting the world today.

After analyzing 14 studies, researchers found that Class 1 malocclusion—where the upper and lower teeth fit together, but individual teeth are misaligned in some way—was the most common. This type of misalignment affected anywhere from 35% to 94% of people, depending on geographical area and age group.

Class 2 malocclusion (overbite) was the next most frequent, with an average rate of 20% across all studies. Class 3 (underbite) was the least common type of malocclusion, affecting about 7% of people across all 14 studies.

Crowding of teeth was also very prevalent, affecting up to 84% of people in some populations. Excess spacing between teeth was also common, seen in up to 60% of people.

How Poor Jaw Structure Leads to Health Issues

Kahn and Ehrlich say that a deformed jaw doesn't only cause dental problems, but can lead to broader health issues as well. In this section we’ll discuss some of the ways poor jaw structure can lead to chronic diseases.

Health Issue #1: TMJ Disorders

First of all, the authors say that a deformed jaw can lead to disorders of the temporomandibular joints (TMJs), which connect your jaw to the rest of your skull.

TMJ disorders have a wide variety of symptoms. The most common of these is chronic pain in the jaw area, especially while chewing or opening the mouth wide (such as when yawning). This can range from mild discomfort to severe pain, and in some cases it radiates into the neck and shoulder.

Other symptoms include clicking or popping sounds when opening or closing the mouth, locked jaw or limited mobility of the jaw, headaches, earaches, and facial pain. Some people also experience dizziness and tinnitus (ringing in the ears).

Physical Activity Is Another Contributing Factor

Another factor in the increasing number of TMJ disorders is bone density—modern humans have less dense bones and joints than our hunter-gatherer ancestors did. Two studies published in the Proceedings of the National Academy of Sciences suggest that the shift to agriculture and a more sedentary lifestyle around 12,000 years ago caused humans to evolve lighter, weaker joints.

One study found that modern human skeletons have 50-75% less dense spongy trabecular bone in their joints compared to other primates and ancient human ancestors. The researchers traced the drop in bone density to the late Pleistocene or early Holocene era, when humans transitioned to farming.

The other study examined archaeological remains and found forager groups had thicker, higher-volume trabecular bone in the hip joint compared to farmer groups, indicating that physical activity level impacts joint bone strength more than diet alone. The researchers conclude that the reduction in physical activity from hunting-gathering to agriculture likely drove the evolutionary changes toward more fragile skeletons in modern humans, which increased the risk of conditions like osteoporosis.

Health Issue #2: Sleep Apnea

Kahn and Ehrlich say that one of the most severe problems arising from poor jaw structure is sleep apnea, a condition where your breathing repeatedly stops and starts while you’re asleep. Sleep apnea happens because when you lie down to sleep, gravity can cause your tongue and other tissues to droop back into the oral cavity and block airflow. If your jaw is underdeveloped then the space in your mouth is already more crowded than it should be, making this more likely to happen.

Sleep apnea causes you to frequently wake up to catch your breath, which prevents you from sleeping deeply and restfully. Because of these sleep disruptions, sleep apnea is known to cause daytime fatigue, depression, and anxiety-related conditions like high blood pressure and heart disease. Young children who suffer from sleep apnea are also at risk for developing learning disabilities, behavioral issues, and psychiatric conditions like Attention Deficit Hyperactivity Disorder (ADHD).

Other Harmful Effects of Sleep Deprivation

The authors note that poor jaw structure may lead to sleep apnea, which prevents you from getting adequate sleep. Neuroscientist Matthew Walker goes into more detail about the dangers of sleep deprivation in his book Why We Sleep, saying that it impairs one's ability to focus and concentrate. The greater the sleep deficit, the more compromised these cognitive abilities become, posing significant risks for those engaged in high-stakes activities like operating vehicles.

Walker also asserts that sleep deprivation hinders emotional regulation. When deprived of sleep, the amygdala—the brain region responsible for emotional processing—can become overactive. This heightens the person’s emotions and makes them less able to control themselves.

As an interesting side note, many people with clinical depression actually report feeling better after a night without sleep. Researchers believe this may be because increased activity in the amygdala helps to counteract the symptoms of depression. However, it’s not clear whether these benefits outweigh the harm that sleep deprivation causes. If you suffer from depression, try discussing wake therapy with a psychologist or therapist before attempting it yourself.

Finally, Walker suggests that insufficient sleep may be a contributing factor to the development of Alzheimer's disease. Sleep loss can interfere with the formation of new memories and disrupt the glymphatic system, which is responsible for clearing out the protein plaques associated with Alzheimer's.

Social Consequences of a Deformed Jaw

Kahn and Ehrlich don't just talk about the physical health issues caused by deformed jaws—they also discuss the possible social impacts of such deformities.

Visibly crowded or crooked teeth can seriously harm people’s self-image and self-confidence. Although that’s not a health condition per se, it does impact their happiness, and therefore their overall well-being. Children and teenagers are especially vulnerable to this: Their peers are likely to bully them for looking different, which can seriously harm their mental and emotional health.

(Shortform note: Childhood trauma, such as severe bullying, can lead to a condition known as Developmental Trauma Disorder, which is similar to Post-Traumatic Stress Disorder (PTSD). Prolonged exposure to stress and adverse experiences during critical stages of development can alter a child's brain and body, impacting their self-perception, relationships, and overall growth. The effects of childhood trauma can persist long after the traumatic events have ended, increasing the risk of high-risk behaviors, addiction, obesity, chronic health issues, and a reduced life expectancy.)

A deformed jaw can also make it hard to speak clearly, which naturally makes communication more difficult. This can hinder people’s ability to make friends, and it can also hold them back professionally—people who have trouble communicating will probably have a harder time finding work, especially in any sort of managerial or leadership role.

(Shortform note: People with speech impediments, as from deformed jaws, don’t just struggle because others have a hard time understanding them; they often face outright discrimination as well. Those with speech impediments—such as stuttering or speaking with a lisp—may endure harsh social stigma and prejudice rooted in misguided assumptions that they are less intelligent, less educated, or less capable than their peers, simply due to their inability to speak as clearly as others do.)

How to Prevent and Correct Poor Jaw Structure

So far we’ve discussed why modern people’s jaws are often deformed and some of the health problems those deformities can cause. We’ll conclude this guide by exploring some of the practices that Kahn and Ehrlich suggest to promote strong jaw development and boost your overall oral health.

The authors add that these measures are especially effective—and important—for children. This is because childhood is a critical growth phase: Jaw development during these formative years can shape not only a person’s dental health, but their overall quality of life well into adulthood. Therefore, Kahn and Ehrlich urge parents to take particular note of these practices and help their children implement them.

(Shortform note: Young children often resist routine hygiene practices like brushing their teeth, along with the other practices we’ll discuss in this section. However, children are hard-wired to imitate the behaviors they observe in their caregivers from a very early age. Therefore, it’s wise for parents to diligently maintain these practices themselves. By modeling conscientious dental hygiene, parents increase the likelihood that their children will follow suit and establish good habits that will benefit them throughout their lifetimes.)

Practice #1: Chew More

Recall that many modern jaw and tooth problems are the result of not chewing enough. Therefore, the most obvious solution is to chew your food more—and, if you have children, encourage them to do the same.

Kahn and Ehrlich say that you should spend at least 30 minutes of each day chewing. You can accomplish this by being mindful while eating: Take small bites and chew each mouthful thoroughly before swallowing. Food should be nearly liquid before you swallow it, so if there are any noticeable chunks left, then you haven’t chewed enough. This also has the added benefit of helping you digest your food more easily.

(Shortform note: Thoroughly chewed food requires less effort from the stomach and intestines to fully break it down and absorb nutrients. This can reduce issues like indigestion, bloating, and constipation, making you feel healthier in addition to helping strengthen your jaw.)

The authors also suggest incorporating tougher foods into your family’s meals, such as whole fruits and raw vegetables. Not only will this force you (and them) to chew more thoroughly—swallowing chunks of such foods would be very unpleasant—they’re also harder to bite through, giving your jaw a better workout. Also, avoid processed foods like packaged bread and frozen dinners as much as possible, because they’re much softer than the types of food your jaw has evolved to eat.

(Shortform note: While chewing more and incorporating tougher foods are effective ways to strengthen your jaw naturally, there are also exercises you can do to make your jaw muscles stronger. These include chewing gum, biting down on a jaw exerciser or rolled-up towel, and performing jaw-clenching and resistance exercises. However, it's important to consult a dentist or physical therapist before starting any jaw-strengthening regimen, as excessive or improper jaw exercises can potentially lead to muscle strain or joint problems.)

Practice #2: Good Oral Posture

Kahn and Ehrlich say that how you hold your mouth normally—meaning while you’re not talking, eating, or doing something else that uses your mouth—plays a significant role in your jaw development and overall oral health. Orthodontists refer to this as oral posture.

Having proper oral posture means that your tongue rests against the roof of your mouth, your lips are closed, and your teeth are lightly touching each other. This position helps to shape your jaw and palate (the roof of your mouth), ensuring that they’re wide enough to comfortably house all of your teeth. Therefore, they advise you to maintain this position as much as possible, and encourage your children to do so as well.

(Shortform note: While oral health experts generally agree with what Kahn and Ehrlich say about oral posture, there is some disagreement over whether the teeth should be touching or slightly apart. Since one of the goals of proper oral posture is to keep the jaw relaxed, it’s best to hold your teeth in the way that feels natural for you and requires the least effort.)

Practice #3: Regular Dental Care

Finally, Kahn and Ehrlich say that preventative dental measures are also key for long-term oral health. Regular visits to the dentist can help identify early signs of issues such as crowding of teeth or potential gum diseases and can treat those conditions if you’re already suffering from them. The authors also advise getting regular dental care for your children, which they say may be even more important than getting it for yourself.

The authors also say that a good dentist or orthodontist should be familiar with forwardontics, which is more formally known as orthotropics. This is a program to evaluate your jaw structure and tooth alignment, identify problems or potential future problems, and treat those problems using various tools and techniques that promote healthy jaw development. In most cases, Kahn and Ehrlich favor this holistic approach over more common dental procedures. For instance, they say that wisdom tooth extractions are usually unnecessary and risk causing permanent damage to the patient’s jaw, teeth, or nerves.

Counterpoint: Forwardontics Is Controversial and Unproven

The efficacy of orthotropics or "forwardontics" is controversial, and its claims are generally viewed with skepticism in the wider medical and dental community. Here are a few common criticisms and concerns about this practice:

1. Forwardontics lacks robust scientific evidence from high-quality clinical studies to support its more ambitious claims about dramatically altering facial structure in adolescents and adults.

2. Some of the proposed practices and treatments carry the potential for adverse effects like muscle strain, temporomandibular joint issues, and tooth shifting if not supervised properly.

3. Forwardontic techniques require diligent compliance on the patients’ part, which can be difficult to maintain long-term.

4. The results appear to be highly variable and limited, especially in fully grown individuals.

Overall, while optimizing oral posture is sensible, orthotropics' ability to significantly remodel facial bones and structure beyond normal growth is unproven and considered pseudoscientific by most dental professionals. Qualified orthodontists can guide proper facial growth in children through proven techniques.

Most experts recommend orthotropic habits for overall oral myofunctional health but remain skeptical of the technique's ability to dramatically alter facial form, especially in adults. More research is needed to substantiate its more ambitious claims.