The process of selecting and securing a partner, whether for conceiving and rearing children, or for enhancing one’s socioeconomic standing, or for attempting motel-room acrobatics, or merely for finding companionship in a cold and lonely universe, is as consequential as it can be inefficient or irresolute. Lives hang in the balance, and yet we have typically relied for our choices on happenstance—offhand referrals, late nights at the office, or the dream of meeting cute.