yawning

[connell]

why do you yawn when you are tired?

[tartanwiz]

To take in more air, passing oxygen into the bloodstream to give you more energy.

[andy hughes]

My colleague has advised the perceived wisdom of this issue, but it has recently been debunked by the discovery that babies in the womb actually yawn as well. The new theory is that it is a promeval signal used by the ape family (of which we are a species) to communicate the need to stay alert. That explains why seeing someone else yawning makes you yawn as well - it's a subconcious trigger to pass the message to the rest of the troup.

[bernardo]

It'd be pretty silly to yawn when you're not tired, wouldn't it?

[darth vader]

Prof. Winston (of BBC fame) gave the same reason recently (just to back up Andy's theory)

[tartanwiz]

If yawning is a sign of communication, why do we yawn alone? And why is it polite to cover up a yawn? Sorry Andy and Darth, but just because a new theory is fresh doesn't necessarily make it a newly discovered truth. Usually it's just an unfounded but publicised idea by some struggling graduate to make a name for themself.

[waynepompey]

More to the point, why do we start to yawn when someone else is yawning ??

[darth vader]

Prof. Winston is a recognised professor and philanthropist. this said i never said that was the reason, just giving a 2nd source to the statement. We yawn alone because (if you believe the theory) it's a communication method from way back. The reason we cover our mouths now is similar to why we keep our mouths shut when eating - cos others don't want to see our gob! waynepompey - see andy's explanation

[melandraf]

also, when we are tired our breathing tends to get more shallow which prompts a yawn to get a good lungfull of oxygen and a big sigh after to get rid of excess carbon-dioxide.

[melandraf]

like Wiz said to start...

[Paul---G]

Good question, but I haven't been able to stop myself yawning!!! Good stuff!!! (Just to prove I can actually spell......... But for some reason my fingers are totally illiterate..........)