Why we yawn?
1. Our bodies induce yawning to drawn in more oxygen or remove a build-up of carbon dioxide.
2. Some think that yawning is something that began with our ancestors, who used yawning to show their teeth and intimidate others.
3. In the dictionary, yawning is said to be caused by boredom, fatigue or drowsiness.
p/s reading about yawning make you yawn. *o*