Why are yawns contagious??

Question

Why are yawns contagious??

Answer 1

From what I've read, the yawn was a sign to sleep back when people lived in tribes. Once a person was yawning the others started to and it was a signal to start going to sleep.

Answer 2

There not really. It's because you are in the same room that has a mix of bad air. Get some air circulating around.  

Answer 3

yawns actually aren't contagious. The thing is, you yawn to get oxygen to your brain to keep you awake. If you're with someone for a long period of time and you yawn, they may be as tired as you, and that would make them yawn as well.