The following manuscript grew out of a desire to understand dental occlusion. Dental school had taught me guidelines for treating bites, but the rationales provided to justify those guidelines just didn't make sense.  Research on bites had been mostly concerned with tracking variables that seem unrelated to patient's overall health or even dental health.  My dental education had made me a good tooth mechanic, but it had not taught me how the teeth work together with the rest of the body.  I felt like dentistry had failed to see the forest through the trees.  

Later, living with the relatively primitive hilltribes of Northern Thailand, I noticed that their chewing was surprisingly smooth and symmetrical.  These people had worn their teeth down significantly, and, from everything I had learned, they should have pathological masticatory systems.  However I noticed their faces were very symmetrical and they showed no signs of the clicking and other TMJ pathologies which were common in my patients back in the US.   The difference was not just a lack of stress in these hilltribes.  There were some people who lived under great stress for various reasons, and they exhibited the same healthy harmonious masticatory systems.  

Later I learned that the same observations have been made and documented by about a half dozen dentists who traveled around the world in the first half of the twentieth century to document the negative health effects of modern civilization on dental health and facial form.  They all noted a dramatic rise in cavities, gum disease, tooth crowding, and facial irregularities that occur whenever traditional cultures give up their traditional life styles and adopt a diet of refined foods, consisting largely of flour, sugar, and processed meats and fats.  At the same time, our health problems have changed from infectious diseases and acute injuries to degenerative diseases and chronic inflammatory conditions. 

Among these early dental researchers, Weston Price had the best photographs.  He showed very clear examples of how, within one generation, the children of parents who had wide symmetrical faces and straight teeth developed narrow and irregular faces with crooked teeth after they abandoned their traditional diets and adopted a diet of modern processed food.  His work is now widely cited as evidence for a diet that avoids grains (Paleo diet).

Now we know that, although some of the changes that Weston Price observed in the health of the traditional people changing to a modern diet were due to a loss of nutritional content, the changes he observed in the faces and teeth of people who abandoned their traditional ways of life were due to the change in the food's texture - not its ingrediants.  The sugar and flour in the modern diet is the cause of the dramatic rise in cavities and gum disease, but the softness of our diet is the cause of the rise in tooth crowding and facial irregularities.  Very similar tooth crowding and facial irregularities can be produced in animals just by softening their food.  Eating a Paleo diet that consists of softened and highly refined versions of the foods that our ancestors ate, like flours made from nuts rather than grains, may very well help some people improve their health for reasons we still do not understand, but it will do nothing to restore the natural straight teeth and well proportioned faces of our ancestors.

TMJ disorders are modern diseases.  They arise all over the world within one generation whenever societies abandon their traditional life styles and adopt a diet of sweetened refined foods. Before the industrialization of food, there was no evidence of the types of TMJ disorders that are common in modern societies today. In the thousands of intact human skulls in museums as well as in the few tribes still living traditional life styles, we can see evidence of arthritic degeneration of the TMJs associated with injuries and extreme tooth wear, but we see no evidence of the dislocated disks, strained and unstable dental occlusions, or asymmetrical retrognathic backwardly rotating facial growth found in many modern TMJ disorder patients.   

TMJ disorders are also developmental diseases.  There is no evidence of them in childhood.  Symptoms start to appear just after puberty, and they become increasingly prevalent throughout the teenage years and into the second and third decades.

TMJ disorders develop as a result of a strained facial growth pattern that has become endemic in modern societies.  Modern facial structures are remarkably longer, narrower, and more retrusive than those from only a couple of centuries ago.  That change in facial growth has occurred much to rapidly for genetic change.  The cause is the weakening of our jaw muscles due to our soft food diet.  Indeed similar changes have been produced in several species of animals by simply softening their diet.  However, facial growth is complex.  It incorporates diverse growth patterns.  To understand how it has changed and why that change has caused TMJ disorders to become prevalent requires first understanding how our jaw systems evolved.