Why do we sleep?

I read some where that fatigue is caused by the bodies inability to acquire enough oxygen to keep everything running. This is what causes yawning, an attempt to get more oxygen. During sleep the bodies oxygen use goes down, while intake reamins about the same, essentially catching up.

Not sure if thats right, but i remember reading it.

 

From which it is easy to prove that caffeine is a good source of oxygen !

 

Hardy har har. But a caffeine high does not feel the same as being well rested.