What Factors Determine a Jawline?

While your genetics greatly determines your jawline, other factors can greatly change the way your jawline will look. 

How often you chew, your habits and your base genetic blueprint determines how your jawline forms. Typically, normal jaw growth involves your jaw growing vertically longer and forward. However, other things can affect your normal jaw development, like mouth breathing, missing teeth, etc.

Normal Craniofacial Development

As you can see from the photo above, the jaw grows longer as you age. Children have vertically short faces because their jawbones are not done growing, and they have small nasal structures. Most children generally have broad faces. 

Children’s mandibles tend to be very retrusive in a profile view. The mandible will naturally grow forward. It is often true, no matter what face type the child has.

The profile straightens during the teen years as the mandible grows more than the maxilla (Palling et al., 2009). The mandible often grows around twice as much as the maxilla. 

The mandible starts to grow a lot when teenagers are 16-18 years old and 18-20 years old. Usually, there is more growth when they are teenagers at 16-18 years old.

The mandible often grows in a forward and upward rotation. That occurs because there is more posterior vertical growth than anterior vertical growth. Additionally, the lower incisors usually tip lingually with age.

There is usually little to no jaw growth when a person reaches 21 years old. It can vary, as some people may have slow growth until they are 25 years old. 

The aging process will also eventually make the jaw smaller. The lower jaw decreases in length and width as people get older. How much the jaw shrinks depends on the person; loss of bone often creates problems with a person’s bite. The combination of bone loss and change in the bite can significantly change the jawline. 

The jaw also tends to jut out with age, as seen in the photo above. 

However, your jaw will grow this way if you have normal facial and jaw development. External factors, like mouth breathing, chewing, etc., can significantly alter your face and jaw. 

Hard VS Soft Diets

When we look at our ancestors, many of them had stronger jawlines and did not need braces. Many researchers did studies and learned that their diet greatly affected their facial and jaw development. 

A study focused on how a hard diet (hunter-gatherer) and a soft diet (agricultural) affected the mandible (Ruff et al., 2011). They used skulls from two American Indian populations to see the differences.

The skulls of the children from both populations were very similar before they began chewing. However, jaw shape often changed in adulthood. Researchers believe that it is likely because of jaw use and diet, not genetics. 

Ancient Cavemen Teeth

Your genetics can determine what you may look like as an adult. However, external factors like your diet and environment also alter the way you look. 

The population with a hard diet primarily ate tough and dried meat, which requires a lot of force to tear and chew. Their jawbones were usually wider and rounder because they had to use more force to eat. 

The population with soft diets that did farming with light hunting did not have the same mandibular expansion as a hard diet population. Researchers believe that they did not get wider jaws because they had to chew less.

The same idea still applies today. The majority of our diets are full of soft, processed foods. Even healthy food like yogurt, soups, etc., are processed and easy to consume, so we use our jaws a lot less than our predecessors. 

However, switching to a hard diet will not be accessible in the world we live in today. Luckily, you can find other ways to strengthen your jaw, like chewing gum. 

Click here to learn how chewing gum can improve your jawline. 


Teeth separate your jawbones and lengthen your face. You feel your teeth touch each time you close your mouth. If you have missing teeth, then your jawbones will not close the same way. Your jawbone will grow smaller over time, and your face may look more compressed. 

Jawline problems become significantly more visible if you got your back molars removed. The back teeth maintain the structure of your jaw and jawline. Therefore, missing back teeth can make your jawline smaller. 

Additionally, the teeth’s roots stimulate your jaw each time you chew. If there are no tooth roots there, the jaw’s bone matter will slowly grow smaller and lose shape. 

The teeth’s size can also affect your jawline. For instance, excessive grinding can make your teeth shorter. Shorter teeth can make you have an asymmetrical jawline.

Your bite can also affect how your jawline looks. For instance, a collapsing bite can move your jaw forward, creating an underbite. An overgrown maxilla and an underdeveloped mandible can cause an overbite. 

For more info on how the bite affects facial aesthetics, check out this Looks Theory episode:

Your Tongue Position

Your tongue position significantly affects your face, jaw growth, and development. The tongue should rest on your palate to stimulate upward and forward facial growth. Proper tongue posture encourages your maxilla to expand and ensure that your jawline grows forward and up, not down.

Mouth Breathing

People who breathe through their mouths instead of their noses often have weak jawlines, especially if they started breathing this way as children. They usually have longer faces with weak cheekbones, jaws, and chins. 

Mouth breathers leave their mouths hanging open with their tongue in a lower position. It works against your craniofacial development. The lack of palate stimulation and position of the mouth, tongue, and jaw can completely change your face shape.

Craniofacial Dystrophy
The process of facial recession and craniofacial dystrophy

The midface often does not grow properly, which is why mouth breathers often have flatter cheekbones. Their lower face usually elongates and narrows instead of growing horizontally and forward. 

Other than facial development, mouth breathing can create a host of other problems. Some examples include obstructive sleep apnea, TMJ symptoms, headaches, pain from poor posture, etc.

Mouth breathing occurs because of child-like habits like thumb sucking and pacifier use. Other causes include chronic open mouth posture, frequent viral infections, allergies, etc.


Mewing is the exact opposite of mouth breathing. Mewing focuses on correcting your tongue posture (along with your neck, shoulder, jaw, and whole-body posture) to stimulate your palate. The palatal stimulation will help direct your jaw and midface to grow correctly.

Mewing Effects
Effects of Mewing and Forward Growth

Mewing can also counteract the effects of mouth breathing. Many people with receding jawlines and chins can often fix it with mewing, provided they catch it while they’re still young. The tongue position will encourage your midface to move up and forward, enhancing the cheekbones and eyes. It also encourages your palate to expand to make your midface wider. 

Keeping your tongue in the correct position will help tighten your jaw muscles. It also helps activate the jaw muscles more to help them grow larger. It can significantly help people who want to get a stronger jawline. 

Results from mewing are the most obvious in children and teenagers. They have softer, malleable bones that are still developing. Therefore, it is easier to mold and encourage your bones to look a certain way as they grow.

However, mewing is still effective for adults. Adults need to mew 24/7 to make sure they get results since their bones are set. What takes six months for a child will take years or decades for an adult. Guiding growth is completely different than trying to get results with bone remodeling. 

Click here to learn more about mewing and your jawline, and check out our ultimate posture guide

Recent Posts