Please note: This is a companion version & not the original book.Sample Book Insights:#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 of the oldest human lineages.#3 The Hadza, a tribe in Tanzania, spend most of their day foraging and hunting. They have no signs of cardiovascular disease, anxiety, or depression. Their activity levels are similar to and even higher than Americans who are more active than usual.#4 The human fossil record shows the appearance, over the past two million years, of anatomical adaptations that make running possible. These include a nuchal ligament, which fixes the base of the skull to the spine, and slow-twitch muscle fibers, which resist fatigue.