From love at first sight and infidelity to hook-up culture and “slow love,” Dr. Helen Fisher, the biological anthropologist and “renowned expert on the science of love” (Scientific American), explains it all in this thoroughly revised classic on the evolution and future of human sex, romance, and partnership. Examining marriage and divorce in 58 societies and adultery in 42 cultures, she argues that we are returning to patterns of business, sex, and love that echo our ancient past . . . and she is optimistic about our future