Humans aren't alone when it comes to yawning — all vertebrates do it too, including fish, amphibians, reptiles, birds and mammals. But why? The "evolutionarily ancient" act of yawning likely serves a ...

Yawning is usually brushed off as a harmless sign of sleepiness, boredom, or lack of focus. In truth, it plays an important role in regulating brain alertness and oxygen levels. While the occasional ...