88. Why do we Yawn?
Source:theloop.ca
Humans are not the only ones that yawn – animals do it too. You are inclined to say that we yawn because we are tired. One of the explanation is that we increase the oxygen level in our blood while we reduce carbon dioxide. But why that happens when we are tired? That is the real question. Some connect yawning with the brain, but that doesn’t make much sense. What do you think?
