Why do we yawn?

This is still a mystery. The scientists are not sure 100%. There are many theories. The main one, says That when We are tired, our brain send information to the lungs to say: "I need oxygen." When we do a big yawn, we do a big effort with our muscles, our face become red and our eyes start cry, Because We introduce a big amount of oxygen and we expel carbon dioxide.

The humans aren't a only specie in do yawns, the animals do it too with 6 seconds on average.

And it happens some courious. Why is contagious yawns when We think About that or when we see somebody yawn?. There are too many theories, but the principal is that We've inherited an habit. This was a sign used by our antecesors, when they didn’t have a language, to comunicate to the group that there was time to sleep or rest.

There are too, a study about yawns that says that it depends on trust: yawns are most contagious with anyone of our confidence, than we are not.

After reading this and watching the video, have been able not to yawn?

"Why do we get sleepy after eating a big meal?"

The nap is a cliche in Spain around the world, that's true, but... we have a justification!

We have two organs that need more energy to work properly in our organism when our eating time ends. This organs are the brain and the intestine. That happen because we don't have red blood cells enought in our brain. why? because the brain send this red blood cells to the intestine to help break down the food and carry the nutrients all over your body.

The rest of the body takes this time to slow down and relax.

So... if you have little blood flow, you feel tired. and... what is the solution? The spanish siesta!