Before the ’60s, models aspired to an adult look, with their up-dos, their severe eyebrows and their stiff poses suggesting a mature, domesticated kind of glamour. “Even if they were 21 they tried to look 30,” says Becky Conekin, a Yale historian who researches mid-century British models. Several major models of that time period were already mothers in their mid-20s by the time they broke into the business. And while the industry always had a taste for thin (one model of the era was described as “a razor-blade dressed up”), the prevailing shape was hourglass. You couldn’t be prepubescent and carry that off.