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.  

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.

They 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.