What does it mean to be a human symbol, of sex or anything else? The death of Raquel Welch at 82 invites us to think about what happens to our sex symbols when they age. What is, after all, the cultural longevity of the bombshell, the femme fatale? We tend to assume that they relinquish this status. Ms. Welch did not. She maintained it, along with her dignity. How is this possible?

Ms. Welch was not primarily an actress, although she acted in dozens of movies. She was an icon of a certain genre, a screen siren of the sexual revolution. Her name became synonymous with a commercial form of eroticism, based on her particular brand of lush beauty: hourglass figure, almond-shaped dark eyes, abundant hair and that famous, equally abundant bosom.

The most indelible image of Ms. Welch’s early career is certainly the famous poster from 1966, advertising her role as Loana, the cave woman in “One Million Years B.C.” In it, she stands on some ancient-looking landscape of sand and rocks, tawny hair over one shoulder, clad in a tattered deerskin bikini. Her pose is at once defiant and welcoming — arms outstretched, legs apart — and a fantasy of bodily perfection from civilization’s prerepressive “id,” seemingly unhindered by the modern constraints of clothing or sexual prudery.

With that role (for which she spoke almost no lines), Ms. Welch acquired the image she would never shake: a woman of nearly primitive, animalistic allure, a living pinup. The New York Times review of the film hailed Ms. Welch as “a marvelous, breathing monument to womanhood,” and therein lay the paradox of her career: Monuments don’t breathe, and they don’t age, either.

While other Hollywood actresses came up in the business by way of the bikini role, Ms. Welch was unusual in that she remained so solidly fixed within the category. Marilyn Monroe was a Playboy cover model who developed into a bona fide movie star during her brief life. Ditto for Jayne Mansfield. Sophia Loren — whose beauty was quite similar to Ms. Welch’s — successfully negotiated a stellar dramatic career. And Jane Fonda totally transcended her Barbarella sexpot poster days to become an acclaimed actress.

Why then did Ms. Welch remain in our imagination as Loana on the poster, even after winning a Golden Globe in 1973 for her role in “The Three Musketeers”? To be sure, she may not have shared those other actresses’ stage skills, but there’s something else. Somehow, Ms. Welch fit perfectly into a very specific American vision of consumable female sexuality, a vision born in the late ’60s but which took root in the ’70s.

In part it’s a look — all hair and cleavage — but also an attitude. Objectified, yes, but self-aware. Quietly confident, even armored in her drop-dead sexiness, available but defiant. The closest comparable contemporary might be Kim Kardashian, who is a star without being an actor, a commodity creating her own brand — Pygmalion and Galatea in one.

To watch Ms. Welch banter with Johnny Carson on his show in 1968 is to see her walk this tightrope. Before she comes onstage, Mr. Carson and his sidekick, Ed McMahon, stammer together about how unnerving they find her beauty. Mr. McMahon jokes nervously about how seeing Ms. Welch backstage had unhinged him completely. Normally glib, Mr. Carson struggles for words to describe her, while making the universal hand gesture for big breasts. When Ms. Welch strides onstage covered up in a high-necked, floor-length dress of angelic white (a sight gag that suggests all three are in on the joke), the two men seem undone by her soft-spoken poise. Asked about being a sex symbol, she says with devastating simplicity, “You can’t fight an image.”

And she never did. Instead, Ms. Welch leaned into it and somehow nature helped her along. Although she may have had some “outside” help maintaining her youthful face and figure, Ms. Welch never looked unnatural or “pulled.” Instead, she looked recognizably like herself until the end. Voluptuous, chiseled, with a face-framing auburn mane.

And, cleverly, she capitalized on that look by marketing a version of it to other women in the form of her successful line of Raquel Welch wigs, which she hawked on QVC. The website for her wigs, all approximating her own hairstyles, featured a lineup of models who resembled Ms. Welch physically, interspersed with photos of Ms. Welch herself wearing the wigs. The message was clear: Buy this simulacrum of part of my body and join me in this array of beauties. A total acceptance, even embrace of the self-fetishizing, body-fragmenting at the heart of so much beauty culture.

That this message was still viable at all when Ms. Welch was over 80 is testament to her unique status. She may never have been a full-blown movie star, but Ms. Welch was a sex symbol all her life. It’s not clear that this is desirable or even possible for other women. And many have suffered in our ageist culture for seeming to try too hard to preserve their appeal after a certain age (even if they might actually be artistically reinventing themselves: See Madonna at this year’s Grammys).

A few notable celebrities have achieved similar longevity. Rita Moreno is a pistol at 90. Ms. Fonda is elegant at 85. Ms. Loren is an elder stateswoman of glamour at 88. But these women do not do “va-va-voom” any longer. They are not self-conscious commodities, or “breathing monuments.” That title belonged only to Raquel Welch; it may retire with her passing — and that’s probably for the best.