But for all the ways those clothes remind us how far women have come, they also shed light on how fast we hit another wall, one that may be even more constricting than everyday girdles and pointy bras. The post-feminist sensibility eschews such gear yet demands flat bellies; it prizes large breasts but also expects them to stand up miraculously.

In other words, if “Mad Men’s” uber-curvaceous Joan Holloway were working on Madison Avenue today, she might visit a plastic surgeon rather than rely on a highly engineered bra. Instead of enduring summer days in stockings, she might endure time in a tanning booth or pay for a spray-on tan. In other words, the Joan Holloways (or Peggy Olsons or Betty Drapers) of today are likely to be goaded into attempting self-transformation on a much larger scale than in the 1960s, when no one bought into the notion that beauty was effortless.

For that you can blame the other 1960s. A friend who came of age then — actually in the early 1970s — talks ruefully about how she used to dye her (naturally dark) leg hair blond so she could then not shave her legs. The goal was to be in step with hippie-centric fashion and its mandate to “be free” but only within certain bounds. Sure this sounds crazy now, but it’s a first glimpse of today’s tyranny of apparently natural gorgeousness that is anything but.