An eye for beauty, for example, locks onto faces that show signs of health and fertility—just as one would predict if it had evolved to help the beholder find the fittest mate.59 The emotions of sympathy, gratitude, guilt, and anger allow people to benefit from cooperation without being exploited by liars and cheats.60 A reputation for toughness and a thirst for revenge were the best defense against aggression in a world in which one could not call 911 to summon the police.61 Children acquire spoken language instinctively but written language only by the sweat of their brow, because spoken
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