When most people think about heterosexuality, they think about sexual and romantic partnerships between women and men, and consequently, they imagine that heterosexuality has an eternal history, a presence as long as human existence itself. But as historians of sexuality have pointed out, the actual history of heterosexuality is far more complicated because while heterosexual behavior has been an enduring and fundamental feature of human experience, the same cannot be said of heterosexual identity, which has a short and remarkably inconstant history (Blank 2012; Katz 1995; Foucault [1978] 1990). For starters, it may come as a surprise that there were no “heterosexuals” until the late nineteenth century. This is because the terms heterosexual and homosexual did not exist until European physicians—all white men—coined and published them in medical journals in the 1860s. But even more striking is the fact that influential European sexologists, such as the Viennese doctor Richard von Krafft-Ebing, asserted that normal sexuality was motivated by an instinct to procreate, and therefore any sex acts that did not result in procreation were unhealthy and in need of medical correction—including many kinds of heterosexual sex. Because women and men could engage in sex acts together that did not result...