Chances are you've already let out an extended, eye-moistening, feel-good yawn or two at this point. I've personally counted six of my own since starting this post.

We've all heard that "yawning is contagious"—but why? In this busy world, we don't sleep as much as we should. Gallup Polls in recent years have found that 56% of Americans report drowsiness as a daytime problem, and 34% of us are "dangerously sleepy." Does seeing someone yawn remind us that we, too, are exhausted are must follow suit?

That may be part of it, but the true reason may go much deeper. As it turns out, yawning may have ancient roots in social bonding.

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