I was eleven when I began to notice the swimmers—teenagers on the team at my local pool. They had a ritual before big meets: The girls would grow out their body hair, and then, the night before all-county or state championships, they’d gather with the boys in one locker room and shave one another clean. The idea was that they’d race faster once the hair was all stripped off. I understood that logic, but what struck me with the most force was the thrill of the ambiguity. One day, you’d glimpse a strong, furry thigh poking out beneath a towel and not know whom it belonged to; then, post-meet, you’d find yourself startled by the gamine smoothness of the boys’ skin, their muscular chests gleaming like polished marble.

I’ve been thinking about the swimmers a lot lately. Down that peeks out from underarms and covers legs seems to be going mainstream. Gender fluidity, and its embrace by the many designers now blurring lines between menswear and womenswear—and swapping clothes between male and female models on their runways—has certainly been a catalyst for the new hirsuteness. In September at the Maison Margiela show in Paris, for example, designer John Galliano made it nearly impossible to tell whether the snake-hipped models wearing his spring collection were boys or girls. You’d see a slim, shaggy calf emerge from a pair of iridescent Mary Janes, and assume boy. And then you’d question that assumption, because millennial women don’t seem all that fussed about body hair.

“I stopped shaving completely about five years ago,” says 28-year-old artist and model Alexandra Marzella, who walks for Eckhaus Latta and poses for Calvin Klein campaigns when she’s not posting au naturel selfies on her Instagram account. “Now I shave occasionally,” she says, “if I feel like it”—a laissez-faire attitude that is resonating with young stars such as Paris Jackson, Amandla Stenberg, and Lourdes Leon. Taking cues from her famous mother, Madonna, who has long declined to shave, Leon arrived at the CFDA/Vogue Fashion Fund awards in a sleeveless white Luar minidress that revealed her own razor rejection. Cheers from the online throngs ensued.

This kind of back-and-forth relationship with body hair is new. When Harriet Lyons and Rebecca Rosenblatt published their 1972 manifesto “Body Hair: The Last Frontier” in the inaugural stand-alone issue of Ms. magazine, they introduced an anti-shaving stance that brooked no compromise. Either you were a shaggy feminist or you were a pawn of the patriarchy, goaded by the pink plastic shaving-industrial complex into spending your money and your time maintaining a key feminine ideal—an ideal of relatively recent vintage. Shaving one’s legs just wasn’t a thing when women wore skirts that swept the floor. It required the broad commercialization of the easy-to-use safety razor, circa World War I—followed by the introduction of King Camp Gillette’s Milady Décolleté razor, a gold-tone tool that came packaged in an imitation ivory box with colored velvet and satin lining—to begin to make it so. According to Rebecca Herzig, the gender and sexuality studies chair at Bates College, in Maine, hairlessness wasn’t firmly established as a beauty standard until after World War II, in that Leave It to Beaver era when American society found it useful to re-entrench gender distinction as soldiers returned home to start families, and to take back the jobs women had held in their stead. “By 1964,” Herzig writes in Plucked: A History of Hair Removal, “surveys indicated that 98 percent of all American women aged fifteen to forty-four were routinely shaving their legs.”