A neuroscientist and journalist offer a revolutionary model of desire, sex, love, and family. Since the dawn of humanity, we've been mystified by desire, love, and the compulsion to bond with others. How do we fall in love, and back out again? What accounts for the variation in the ways people express love, and toward whom? What force keeps people together, and, if it's so powerful, how can anybody ever cheat? With award-winning journalist Brian Alexander, neuroscientist Larry Young peers inside the living brain to discover how chemicals acting on circuits drive such seemingly complex behaviors. It turns out that on a molecular level, love is not so mysterious after all. The authors explain the mechanisms behind emotional bonding, physical attraction, jealousy, infidelity, and the very essence of what it means to be human. Young and Alexander offer nothing less than a grand unified theory of love, sex, gender, sexual orientation and family life that's sure to prove both enlightening and controversial.