A human with the metabolism of a hummingbird would need to eat about 80,000 calories a day to survive. That's because staying warm by making your own heat takes a ton of energy; creating your own body heat is incredibly expensive. So, why aren't cold-blooded… like crocodiles? Here's the science.

Hold on to your butts. This episode is about… butts. The science and evolutionary history of your rear end, the down-low on your derriere, shining a little light where the sun don't shine… you get the picture. But(t) seriously, we don't talk about this all-important hole enough, and how, from an evolutionary perspective, it might be the most important orifice on your body.