Please note: This is a companion version & not the original book. #1 The runner's high is often described as a lure for reluctant exercisers. However, the high emerges only after a significant effort. It seems to be the brain's way of rewarding you for working hard. #2 The Hadza are one of the last hunter-gatherer tribes in Africa. They live in an environment close to the one in which modern humans evolved, and their DNA reveals that they are one...