Curiosity Topic

I Wonder Why.........People Yawn

Everybody yawns, from unborn babies to the oldest great-grandparent. Animals do it, too. But why, exactly, do people and animals yawn? No one knows for sure. But there are many theories about why people yawn. 

One is that when we are bored or tired, we just don't breathe as deeply as we usually do. As this theory goes, our bodies take in less oxygen because our breathing has decreased. Therefore, yawning helps us bring more oxygen into the blood and move more carbon dioxide out of the blood.

Yawning, then, would be an instinctive reflex to help us control our oxygen and carbon dioxide levels. Sounds good, but other considerations have shown that breathing more oxygen does not decrease yawning. Likewise, breathing more carbon dioxide does not increase yawning. Now what?

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. 

But there is one idea about yawning that everyone knows to be true. It seems contagious. If you yawn in class, you'll probably notice a few other people will start yawning, too.