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why do we yawn?
Yawning is a familiar behavior characterized by a large gaping of the mouth, accompanied by a deep inhalation of air, followed a shorter expiration. This behavior is under involuntary control, so it cannot be consciously controlled or suppressed. Further, yawning is a stereotyped behavior expressed by all classes of animals, and is correlated by a variety of neurochemical changes in the brain. Previous research suggests that yawning is a biological mechanism in humans and non-human apes, such as chimpanzees, to keep the brain from overheating.

Another theory is that yawning stretches the lungs and lung tissue. Stretching and yawning may be a way to flex muscles and joints, increase heart rate, and feel more awake.

Other people believe that yawning is a protective reflex to redistribute the oil-like substance called surfactant that helps keep lungs lubricated inside and keeps them from collapsing. So, if we didn't yawn, according to this theory, taking a deep breath would become harder and harder.


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