When you walk into the classroom you instantly KNOW this is the cool teacher.

It's a good thing we haven't evolved like this. if a lot of diseases could get in like that then there's a point to it. It helps keep population control. Our structure allows oxygen, and we shouldn't ask why. Humans would probably live longer if we did, and that's a bad thing considering the current population.

Just imagine his upper body strength!

Ok, we haven’t done this because oxygen is used in our cells. Without them, we would die.