at least I covered my mouth

My science professor reassured one of my classmates that the lecture was almost over, because he was caught yawning.

"I saw you too," he said, pointing out that I too had yawned.

I felt bad. It was not a boring lecture. My yawn was merely an involuntary domino effect from the other kid's yawn. It was also nearing 5 o'clock on a long day that had started at 8 that morning.

Yawns are so interesting. I thought it was always the body's way of correcting an oxygen deficiency. Apparently there are a lot of theories on why we yawn, and no correct answer.

According to HowStuffWorks.com, there are three main rationales:

1. The physiological theory: When we are in carbon-dioxide concentration environments, a yawn attempts to counter the excess of CO2 by drawing more oxygen into our lungs. If a group is sitting in the same room (same CO2 enivornment), then every member may need to correct the imbalance; this explains why yawning may appear to be contagious.

2. The evolution theory: Our primitive ancestors may have shown teeth or opened their mouths widely to a signal the time to switch activities. Modern day yawns communicate the same message--suggesting the end of a boring activity in exchange for the progression to something more fun.

3. The boredom theory: Yawning is just a tell-tale sign that you are tired and/or bored.

I think that it is probably a mix of theory one and three. I can see fatigue playing a big part, and mainly why I was yawning in class last Thursday. I do not know much about science or biology so I pretty much agree with the physiological explanation purely on the trust that professionals have some idea what they are talking about.

One thing that seems to be a universal truth about yawning is that it is involuntary. I do not know why it is considered rude to yawn; no one can help it.

Teach, it might not even be related to your lecture. I might have just had a late night, and/or long day. Do not take it personally.

Here are some fun facts about yawning:

The average yawn lasts about six seconds.

Your heart rate can rise as much as 30 percent during a yawn.

55 percent of people will yawn within five minutes of seeing someone else yawn.

Blind people yawn more after hearing an audio tape of people yawning.

Reading about yawning will make you yawn.

Olympic athletes often yawn before competition

Did you yawn while you read this post?