Yawning does serve a purpose: it wakes you up
Yawning is an interesting activity. Just thinking about it has made me yawn twice as I’ve written about it. Seeing other people, and sometimes other mammals, yawn will trigger it. So what’s the point? Turns out it is to wake you up and trigger your brain into action:
Yawning is not something we usually aim to provoke among our readers, but have a yawn now. Does your brain feel cooler? Do you feel more attentive? According to psychologists Andrew Gallup and Gordon Gallup of the State University of New York at Albany, that is why we yawn: to boost blood flow and chill the brain.
Not only that, brain-cooling explains why you can “catch” a yawn, says Gordon Gallup. “We think contagious yawning is triggered by empathic mechanisms which function to maintain group vigilance.” In other words, yawn-catching evolved to help raise the attentiveness of the whole group. Source: Yawning may boost brain’s alertness - being-human - 02 July 2007 - New Scientist
I always thought it was a just an oxygen boost for your brain. I was close, but not quite. I like the group yawn theory. Imagine being a hunter-gatherer in the bush hunting. One person yawns triggering others as a signal to sharpen up. Handy, very handy. So the hunter who napped might have become lunch for something or left behind.
Hat tip: Boing Boing