The Myth of Yawning

Today during my 'wonderful' Psychology lesson i was feeling rather tierd, this was mainly because it was the afternoon and the college decided to put the heating right up, but anyway we were not doing much in the lesson and i kept yawning and i then became easily distracted by the fact after i had yawned the other people in the class were also yawing a few seconds later as if i was passing on this contagious disease or something. So anyway it made me think 'Do we yawn because of the lack of oxygen in our body?'. So being the sado i am i decided to look it up, as i had nothing better to do, and to my supirse yawning infact has nothing to do with lack of oxygen. Yawning is seen as a soical sign and the yawn may have evolved from a behavior during which animals showed their teeth to indicate that it was time for the pack to settle down for the evening. Hmmmmmmm how very interesting..... So if that be true, was i telling my fellow classmates that it was time for us to settle down and sleep??