Go ahead; admit it—you’re yawning right now. That’s OK, we forgive you. We know it’s not because you’re bored. It’s just that seeing other people yawn, reading about yawning, or even just thinking about it can make you yawn. And it’s a good thing, too: Passing yawns around a campfi re might have kept our ancestors alive.
Picking up another person’s yawn may be an empathetic refl ex, says evolutionary psychologist Gordon Gallup of the State University of New York at Albany. When you see someone yawn, neurons in your brain fi re and cause you to “feel” what that person is experiencing, commanding you to perform the action even if you don’t actually feel the need.
Scientists have yet to figure out why we yawn at all, though. Some say it signals boredom, whereas others have suggested that it balances carbon dioxide and oxygen levels in the blood. Most recently, Gallup theorized in a study last year that yawns cool our brains so that they run effi ciently, similar to running a fan in a computer. He found that, contrary to common perception, cooling the brain with a yawn keeps people from nodding off.
Alternatively, E.O. Smith, an emeritus professor of anthropology at Emory University, contends that yawning may have encouraged our ancestors to go to bed early. “Contagious yawning didn’t arise in a vacuum on a Saturday afternoon,” Smith says. Spreading a case of the yawns around a bonfi re, he posits, may have prompted night owls to climb up into their comfy tree beds with their sleepier brethren, out of danger from stealthy predators.
*.* Source of Information : May 2008 Popular Science