“Most of us equate yawning with being tired, but studies have found that yawning could be caused by your body trying to cool your brain,” Dr. Jen Caudle tells Yahoo Life. She describes yawning as the ...

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 ...