Natural "Brain Drugs" Turned Us Into Endurance Athletes

Ever wonder why us humans (well some of us at least) love to go for long runs and do other forms of endurance exercise? Most animals don't share that trait, so what sets us apart? New research has found that the natural brain drugs responsible for the "runner's high" effect -- called endocanabinoids and endorphins -- caused us to evolve into biped distance runners.

Very intesting stuff here: Runner's High Motivated the Evolution of Exercise, Research Suggests