Married Love, a 1918 treatise by the British scientist Marie Stopes, changed that. Stopes’s book was one of the first popular texts to propose that women’s sexual desire was not only natural and universal, but an attribute that husbands would do well to attend to. Stopes didn’t mince words; most men entered into marriage not knowing how to sexually satisfy a woman, while most women didn’t grasp what the sexual encounter should entail. Stopes describes how sex should involve a real pleasure ‘which should sweep over every wife each time she and her husband unite. The key which unlocks this electric force in his wife must reverently be sought by every husband.’ In the same breath, Stopes made the bold hypothesis that men who had lost their virginity to prostitutes prior to getting married were inclined to mistake their paid sex partner’s yawps and quivers for a testament to their own sexual prowess; these same men were also likely, in turn, to blame their future wives’ lack of sexual arousal on what they perceived was her frigidity instead of their own shortcomings in the sack. (A hubristic misconception that many straight women would surely affirm has stood the test of time.)