Short answers, pulled from the story.
Human sexuality is the way people experience and express themselves through sexual activities, involving biological, psychological, physical, erotic, emotional, social, and spiritual feelings and behaviors. Because it is a broad term that has varied across historical contexts, it lacks a precise definition. Interest in sexual activity normally increases when an individual reaches puberty.
Research finds considerably more evidence supporting innate causes of sexual orientation than learned ones, especially for males. This evidence includes the cross-cultural correlation of homosexuality with childhood gender nonconformity, moderate genetic influences in twin studies, prenatal hormonal effects on brain organization, and the fraternal birth order effect. Hypothesized social causes are supported by only weak evidence.
William Masters, a physician, and Virginia Johnson, a behavioral scientist, created the sexual response cycle model. Known as the EPOR model, it consists of four phases: excitement, plateau, orgasm, and resolution. They opened the first sex therapy clinic in 1965 and described their techniques in their 1970 book Human Sexual Inadequacy.
Alfred Kinsey initiated the modern era of sex research, first collecting data from questionnaires given to his students at Indiana University before switching to personal interviews. He and his colleagues sampled 5,300 men and 5,940 women. He found that most people masturbated, many engaged in oral sex, women are capable of multiple orgasms, and many men had had some homosexual experience.
William Masters and Virginia Johnson opened the first sex therapy clinic in 1965. They had directly observed and recorded 10,000 episodes of sexual acts between 312 men and 382 women in laboratory settings.
European colonizers encountered non-European cultures whose sexuality and gender differed from European heterosexual cisnormativity, and they imposed their own norms in response. In America, 155 native tribes are recorded as having embraced two-spirit people, who fall under a third gender category and were revered for special wisdom. The Religious Crime Code of the 1880s aimed to attack Native sexual and marriage practices.
Birth control began to lose stigma in 1936, when the ruling in U.S. v. One Package declared that prescribing contraception to save a person's life or well-being was no longer illegal under the Comstock Law. By 1938 there were 347 birth control clinics in the United States, though advertising their services remained illegal.