What goes around comes around. The Twenties, Sixties and Eighties have each had their turn on the fashion carousel, but if there’s a true stylistic boomerang, it’s the Seventies. Forget the caricatures of disco and polyester; the real legacy is far more subtle—narrow silhouettes, goddess gowns, safari jackets and classic American sportswear. Such a lasting grip is owed to the clothes’ enduring wearability. Case in point: The recent resort collections—lines designed to sell, sell, sell—were packed with Seventies sportif.