Ants are, so far, the only non-mammal species that demonstrate drug-seeking behavior.
Over the course of human civilization, men have evolved more feminine traits.
Smooching feels good, of course, but couples first started swapping saliva as a way to test out genetic compatibility.
Every season several football players miss a number of games after absorbing vicious blows to the head.
It would probably make a pretty cheesy horror movie, but the thing is, it's true. In fact, that creature with the extra brain is you.