The science behind yawning and its mysterious behavior Humans aren't alone when it comes to yawning — all vertebrates do it too, including fish, amphibians, reptiles, birds and mammals. But why?

When yawning horizontally, you should feel a different stretch in the back of your mouth and throat that targets your soft palate. ‘Yawn a lot,’ says actor Morgan Freeman.

Yawning is often seen as a simple sign of fatigue or boredom. However, this natural and universal reflex could reveal much more about your hormonal health—particularly your levels of cortisol ...