There are a several theories about yawning and why people yawn. While medical personnel and researchers have a good idea about the cause, some of the story on yawning remains a mystery.

Most people understand that human beings yawn when they are tired and need to rest. But we also yawn after we wake up in the morning. Research has asked the question: Is there a connection between night yawning and morning yawns?

The one absolute truth about yawning is that it’s not a voluntary action. Animals, including humans, yawn involuntarily. Some people believe that we yawn because of a low level of oxygen in the blood.This theory indicates that a yawn causes us to inhale a large amount of air to replenish the oxygen. But research shows that people don’t yawn in response to all low-oxygen levels in the blood (hypoxia).
Apparently we yawn when we are tired and blood oxygen is low but not in other hypoxia situations (such as activity at high-altitudes).

Other Theories About Yawning Include:

 People yawn to communicate with others about being weary or depressed, or something similar.

• Yawning stretches the lungs (!) to get them ready in the morning. This theory doesn’t stand up to reality.

 Yawning helps stretch facial muscles and involves a few other muscles of the body, including the abdomen and diaphragm.

The first theory about communication is close to the mark, according to most scientific research. Some theories state that we yawn at night when we are tired and in the morning when we wake up, and the reasons are somewhat the same. Animals, including human beings, yawn when they are tired and when they are waking up to coordinate with others in their community or group. It could be that leaders of a group signal others that it is time to bed down for the night. One individual might also signal others that it is time to start the day.

One thing that is definitely known about yawning is that it is involuntary, as mentioned. It causes animals to open their mouths and take a deep breath at particular times. Medical research has shown that even a fetus will yawn (as early as 11 weeks). Some have theorized that one person might yawn after seeing another do it, as a show of empathy. This fits with the idea mentioned earlier about group communication. Yawning does seem to be contagious, in this sense.

Science has, in recent years, put forward the theory that yawning “cools the brain” if the brain is overheated. If the surrounding temperature and/or the body temperature are too high for comfort and efficient brain activity, we may yawn. Root causes for this activity can include exhaustion and lack of sleep, both of which may cause the temperature of the brain to increase. Apparently some who suffer from epilepsy and other neurological conditions might experience an excess of yawning.

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Lucas Beaumont
Generalist. Wikipedia contributor. Elementary school teacher from Saskatchewan, Canada.