Until just a few years ago, gender dysphoria—severe discomfort in one’s biological sex—was vanishingly rare. It was typically found in less than .01 percent of the population, emerged in early childhood, and afflicted males almost exclusively. But today whole groups of female friends in colleges, high schools, and even middle schools across the country are coming out as “transgender.” These are girls who had never experienced any discomfort in their biological sex until they