Why do we yawn? Is there any purpose to it?

[soonny]

Any idea anybody?

[darth vader]

I was led to believe it is the mind's way of getting us to intake some fresh air

[Squirrel]

There's also a fun trick my teacher told me when I was 11: start yawning in a room full of people. Hearing this, people's brains will think "Uh oh - that guy's yawning - there must be a shortage of oxygen in here or something" and begin to yawn as well, even if they're not tired! I was told the reason for yawning when sleepy was due to the brain slowing the body's functions down and slowing the breathing rate accordingly. If you got so tired that you started breathing a little too slow then a yawn or two would even out the gas levels in the blood.

[xyzzyplugh]

But.. as pointed out b4.. [by me] a yawn does Not involve a sharp or even a deep intake of breath.; back to the drawing boards everybody :-)

[Nelli]

It is the bodys way of increasing the amount of Oxygen in the blood.

[Nelli]

My doctor told me this as, I used to suffer from hyperventilating, and I often used to yawn just before an attack, and this he told me is because my body is trying to rectify the balance of oxygen in my bloodstream.

[ksl]

i heard it was a habbit from when you're inside the womb (why you did it in the first pace i don't know) and we don't actually need to yawn!

[soonny]

okay... then how do we account for the fact that our eyes water everytime we yawn?

[pop n fresh]

yawning comes from our animal instinct, like the lions in the desert sat under a tree. when they yawn they show their teeth, they are saying yes im sleepy and im sat here but dont attack me because i will bite you with these big sharp teeth. we do the same as the lions. the reason other people yawn when we yawn is because they see us show our teeth so they show their teeth. it is like saying big deal i have them too and i will bite you. its just our animal instinct warning others to stay clear.

[soonny]

I guess it would suck for people with dentures then. ^_^ Thanks for the feedbacks.