Can you explain this?

Why do we Yawn?? I have heard so many different reasons as to why we Yawn, but what is the correct medical reason for it??
My Mom and I were talking on the phone and we both had the "Yawns" Then we started talking about the fact that some folks believe that the reason we yawn is because there is a lack of oxygen to the brain...but then why is it that if we see or in our case hear someone yawn it makes us do the same thing.
Crazy question I know, but I bet you have wondered the same thing once or twice.
How do you explain it?

Just realized I yawned as I was reading. Now yawned as I was typing. Going back to bed.

we yawn because oxygen levels in our lungs are low. Studies have shown that during normal, at-rest breathing, we don’t use anywhere near our lung capacity; for the most part, we just use the air sacs at the bottom of the lungs. If the air sacs, called alveoli, don’t get fresh air, they partially collapse and the lungs stiffen a bit. As a result, it’s believed, our brain prompts the body to either sigh or take a yawn to get more air into the lungs.

But why are they so contagious?

My thoughts exactly John! LOL

Isn't is supposed to be some kind of a threatening or greeting behavior from our ancient past? This kind of thing is seen in babboons and other primates too. Because it IS contagious, it must have served some type of ancient function that we no longer need.

I'm sitting here yawning just thinking about baboons yawning! ROFL

yawning here too! lol

same way when you see someone scratch an itch and you end up scratching as well. *scratch* *scratch*

CoCo! Stop it! *streeeeeeeeetch*

Allie is 2 months old and if you yawn, she does too. Every baby I've ever met does it, how does that work??

That's true tiG, babies DO get it too! Yawns truly are contagious, and yes, while reading this & contemplating yawns I finally yawned myself, even though I haven't yawned in hours, lol. It's always been amazing to me that yawns are contagious even if you see someone on tv do it, or hear someone -- like on the phone -- but reading/thinking about it? That's new for me!

Canines yawn to calm the pack. Or so I was taught when studying wolves in Yellowstone. The alphas raise their heads & yawn when things have been nervous and now it is time to just mellow out. It's a reasurance signal. I used this technique with my dog actually. When he was younger he'd get nervous whenever we were in the car. Of course I couldn't do much about his behavior while driving & finally tried yawning & softening my whole body to simulate relaxation as much as possible. It worked wonderfully.