" Darwin’s great gift to science was simplifying all life to pure mathematics: your one and only goal on earth is multiplication. Everything you do, every instinct you have, is an evolutionary urge to make babies and leave behind as many copies of yourself as possible. From that perspective, heroism makes no sense. Why risk the grave for someone else if there’s no guarantee of a biological payoff? Dying for your own kids: smart. Dying for a rival’s? Genetic suicide. "

― Christopher McDougall , Natural Born Heroes: How a Daring Band of Misfits Mastered the Lost Secrets of Strength and Endurance