Is Jaw Shape Genetic?

A defined and well-proportioned jaw is an ideal facial trait. But how much of it is genetic, and how much of it is environmental?

Your jaw shape is usually based on your genetics. However, it is only an estimate because many other factors can determine your jaw shape, too. Your jaw shape can also be affected by your body fat percentage, jaw muscles, diet, etc.

Your Jaw Shape and Genetics

Like with the rest of your body, your jaw shape can be significantly determined by your genetics. Genetics or heritability estimates 45-85% of bone density, structure, and mass (Leonary et al., 2012). For instance, if both of your parents have a square jaw, you will likely have one too.

However, think about your genetics like blueprints. Your genetics can determine what your jaw shape is supposed to look like.

Although not everything will go to plan, other factors can influence how your bones will grow. Some factors that affect your jaw shape include:

  • Diet
  • Body Fat
  • Jaw Muscles

Therefore, your genetics is more of an estimate of your jaw shape. It will not precisely determine what your jaw shape will be.

Now let us take a look at how your diet can affect your jaw shape.

Your Jaw Shape and Diet

While your genetics can determine a great deal of your jaw shape, it also depends on other factors like your diet. For instance, if a person is malnourished as they develop, they may not reach their full potential in height. That is because their bones did not get enough nourishment to grow. The same can be said about your jaw shape because of your jaw bone. Poor nutrition, particularly calcium and vitamin D deficiencies, could cause crooked teeth and poor jaw growth.

There is no hard evidence on how much nutrition can affect a person’s jaw growth. However, your jaw bone growth may slow down or pause if you lack proper nutrition since diet can affect your skeletal growth.

However, there is another way diet can affect your jaw shape. Studies have shown how soft-foods and hard-foods can affect your jaw shape. The mandible, or lower jaw, changed in size based on the diet. For instance, hunter-gatherers have narrower and longer mandibles than agriculturalists (Noreen von Cramon-Taubadel et al., 2011).

For instance, another study was done to compare two groups of people from the 1600-17000s. One group ate a hard diet, whereas the other chose a softer diet. The researchers compared the jawbones of the children for both groups, and they were similar in shape. However, the jawbones were different in adulthood (Ruff et al., 2011).

The group that ate a hard diet had wide and round jawbones. Researchers believe that it was because of the force they had to chew and the amount they chewed. On the other hand, the group with a soft diet did not have that jaw expansion. Researchers believe that it was because they chewed less and did not have to use as much force.

Therefore, the amount you chew and how much pressure you use as you grow can affect your lower jaw structure.

Your Jaw Shape and Body Fat

Your jaw fat zone is a long compartment that starts at your hairline and above your temple. It extends to your jaw. This area can store fat.

You fill that compartment when you have a lot of excess body fat. It can change the shape of your face, including your jaw shape. Your jawline becomes fuzzy looking and can become round. That is because the fat layers are obscuring your jaw shape. If you continue to add fat to this compartment, the lower part will droop past the jaw. It creates a jowl, which makes you look older and hides your jaw shape even more.

Zac Efron is an example of how extra body fat can change your jaw shape. Zac Efron has a rectangular face with a prominent jawline. However, his jaw shape was round and soft when he had excess body fat.

Doing facial exercises and losing weight can help you lose excess fat. However, this process may take a while for you to see results. Additionally, losing a few pounds may not be enough to reveal your jaw shape. You need to aim for a low body fat percentage if you want a really defined jawline.

Most runway models that we see have very defined jawlines. That is because their body fat is very low. So your aim should be to lose weight until you have abs. Your body fat percentage should be very low by that point, and your jaw shape should reveal itself.

However, if you do this and your jaw shape is still the same, the problem may be your jaw muscles, which brings me to my next point.

Your Jaw Shape and Jaw Muscles

Jaw muscles can help make your jaw look more defined and prominent. However, huge jaw muscles can make your jaw look too big and make your face asymmetrical.

The more that you use your jaw muscles, the larger they get. While this may be a good thing if you want to have a more prominent jaw, some people may dislike the increase in size.

Enlarged jaw muscles can make the jaw look too square. However, some people may have a softened and bulging jaw shape. Your jaw shape can be uneven if only one side of your jaw has enlarged jaw muscles.

Frequent or constant clenching or grinding of your teeth can make your jaw muscles larger. Of course, this means constant or frequent chewing can lead to enlarged jaw muscles. If you are regularly chewing gum, it can make your jaw muscles larger. Grinding or clenching your teeth from stress, while you sleep, etc. can also make your jaw muscles grow.

Some people may have a temporomandibular disorder or TMD. This condition can cause jaw pain, and you may lose control of your jaw movement. It can lead to uncontrolled grinding, clenching, chewing, etc. and enlarged jaw muscles.

Masseter hypertrophy is a rare condition. It makes your jaw muscles bigger. Most people only experience this on one side of their jaw, which causes facial asymmetry.

However, some people can have it on both sides of their jaw. It can make your jaw look too large and wide. Even if you have it on both sides of your jaw, it may still look uneven. Treatment for enlarged jaw muscles will depend on the cause. For instance, an orthodontist may grind down teeth to enhance the bite if you have TMD.

There is no specific cure for masseter hypertrophy. However, many people have been using Botox injections to treat masseter hypertrophy. Botox is well-known for reducing skin wrinkles. However, it is also an effective drug that can treat some muscle conditions like masseter hypertrophy. 

Botox is created from a toxin. However, when used in small doses and used correctly, it can be used for cosmetic and medical purposes. Botox injections make your jaw muscles relaxed. People with TMD may lessen or stop experiencing uncontrolled jaw movement. People with masseter hypertrophy can experience a decrease in their jaw muscle size. However, the only downside to Botox injections is that they do not last long. It usually lasts for about 3-4 months for most people. It may last for six months for certain people.

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