At the gala opening of the Metropolitan Museum of Art's New Greek and Roman Galleries, last spring, the cynosure in the skylit atrium was neither a society starlet in borrowed couture nor one of her 2,000-year-old marmoreal counterparts. Those creamy Venuses and saturnine Muses were too fleshy for this fashionable group's tastes. Rather, the scene-stealer of the evening was the strapping, bearded first-century-A.D. Hercules—a "bear" in current gay parlance—his Nemean lionskin knotted proudly at his sternum.

"Can someone get me a date with that man?" one guest asked repeatedly.

I'm fairly certain that four decades ago (or maybe four minutes ago?) this brawny Hercules would have appeared embarrassingly overdeveloped—a hirsute sack of walnuts, Victor Mature on a bad day. Compare him, for the sake of argument, to another archetypal male effigy, the crew-cut Ken of my girlhood, circa 1964. At that moment, the torso of Barbie's consort was molded more along the lines of a worm than a hero. The pinup boy of my adolescence, Jim Morrison, was scrawnier still, a cadaverous martyred Christ. Even the considerably less androgynous beefcakes of my mother's and grandmother's generations—Clark Gable, Cary Grant, John Wayne, Ronald Reagan, Montgomery Clift, Kirk Douglas—had no distinct cuts in their physiques, unless you count the clefts in their chins. And their waistlines sat somewhere in the vicinity of their diaphragms, not—as an Akon video or a 2(x)ist underwear ad might suggest today—at the latitude of their pelvises.

The turn-of-the-21st-century downward drift of the waistline (it's begun to creep back up again, but uncertainly)—and the concomitant fixation on "core" abdominal-muscle definition—was a phenomenon brought to you by trendsetters high and low: Tom Ford, Britney Spears, and the beltless fellows in the cellblock. Historically, styles in bodies have followed the lead of fashions in clothing and just as quickly become passé. Rubens's pillowy ladies shimmer and swell like the voluminous satins of their era; the belly of van Eyck's prelapsarian Eve bulges in the same manner as the elegant gowns of 1430; the elevated breasts, rigid back, and wasp waist of Goya's Nude Maja echo the modish outlines of the sitter's discarded corset; and the sleek, low-slung bottoms and breasts of Howard Chandler Christy's nymphs at the Cafe des Artistes seem to have just fallen out of clingy, bias-cut Vionnets from the 30s. Accurate or not, period costumes in film are rarely convincing, because the bodies beneath them are anachronisms.

The android-y aesthetic of the pumped-up he-man with washboard abs (think 50 Cent)—which percolated into mainstream consciousness from gay and black subcultures—has even infiltrated the design of sneakers, and of automobiles, once dominated by female anatomical references. (The jutting, red-tipped taillights of a 1958 Chrysler Imperial Le Baron could make a grown man blush.)

These are not examples of meaningless and coincidental pseudomorphic resemblances. "The idea of fitness, being taut, athletic, pinched, does imbue car design today," says Joe Richardson, national brand RR. manager for Mercedes-Benz USA, who cites as an example the 2007 S-Class sedan's "muscular shoulders." Likewise, the upswept, compact tails on vehicles from Nissan Maximas to BMW R 1200 motorcycles reflect, in my opinion, the recent veneration of pneumatic, high-set backsides, a predilection that has led, says New York plastic surgeon Dr. Gerald Imber, to an increased demand for silicone butt implants (a procedure he won't perform). And the V-8 engine tucked into the 2004 Maserati Coupe Cambiocorsa, to my eyes at least, resembles nothing so much as the powerful, ripped six-pack of the bearded Hercules, back at the Metropolitan Museum.

Surprisingly, at least for contemporary viewers, this Hercules (who once adorned a Roman bath) is not colossally scaled everywhere. In ancient Greece and Rome, men and women preferred "the dainty penis," says John R. Clarke, professor of art history at the University of Texas at Austin and author of Roman Sex. A large penis was considered "grotesque and comical," more suitable for freakish figures such as Satyrs than for gods, athletes, or heroes. A hunky man, dramatist Aristophanes wrote in 423 B.C., had "a shining breast, a bright skin, big shoulders, a minute tongue, a big rump, and a small prick."

Predictably, just as the popular image of masculinity has hit a steroid-and-testosterone-fueled extreme, fashion designers have gone back to the drawing board and come up with a corrective antithesis. "The gym body has almost become a cliche," observes Ralph Pucci, whose firm, Pucci International, manufactures display mannequins for upmarket retailers. Agrees Simon Doonan, creative director of Barneys New York, "Sample sizes for men have never been so tiny. Male models have never been so concave. They're on low-carb diets, and they don't work out anymore—they jog. It's a look coming out of Paris, from Hedi Slimane. It's intellectual rather than sexy—definitely not an image gay men are slobbering over."

The schism between elite fashion sensibilities and vernacuIlar tastes is even wider where women are concerned. While fashion models, notoriously, are mutating into ever more attenuated, long-necked, sharp-contoured, and small-headed creatures (gaunt proportions last seen in the sculptures of Alberto Giacometti or maybe the jamb statues of the Chartres Cathedral), stacked Russ Meyer-type fetish bimbos are overrunning the mass media (The Girls Next Door, The Real Housewives of Orange County, the Pussycat Dolls, or any girlfriend of Quagmire, the pervert on Family Guy). At the Metropolitan Museum Costume Institute's gala last May, Jessica Simpson looked almost as out of context as Stella Tennant would have at the Playboy Mansion. The flip side of anorexic chic is not, in my opinion, morbid obesity, but inflatable-sex-doll-style self-mortification, via knives, needles, treadmills, hair extensions, fake tans, fake teeth, fake nails, and full Brazilians. It's a cyber-age variation on Munchausen syndrome that makes old-fashioned tight-lacing and garden-variety female masochism seem wholesome by comparison.

"I find it incomprehensible that, after the feminism of Kate Millett and Betty Friedan, women would turn themselves into an army of Stepford porno chicks with shop-bought hooters," says Simon Doonan. Observes psychoanalyst Dr. Janice S. Lieberman, a specialist in narcissistic body-awareness disorders, "Instead of working at a job, these women work on their bodies, almost as a moral imperative. It's a backlash against feminism, a symptom of accelerated upward mobility, a consequence of inadequate nurturing, and a way of having control in otherwise scary times."

Ariel Levy, author of Female Chauvinist Pigs, says, "One image of women—promoted by fashion—is impossibly complex, coded, and conceptual, and the other is in-your-face crass, anti-intellectual, pop as it can be, accessible as the Internet porn on which it's based, and absolute science fiction."

The fiction, as far as breasts go, is less about size than shape. Jane Russell's 40s Outlaw bosom—cantilevered into twin projectile missiles by Howard Hughes's aeronautically engineered brassiere—still reads as real. The perfect big tits on 50s Vargas cheesecake, the flawless little ones on René Gruau's 70s Lido girls, and the ideal pair on Peggy Moffitt in Rudi Gernreich's 1964 topless bathing suit, dip and tilt anatomically—an organic, teardrop silhouette difficult to replicate in the operating room. Today's standard-issue synthetic breasts have the subtlety of bowling balls, and underpinnings are devised to squeeze them together, not "lift and separate" them as the old Playtex TV ads used to promise. "You lie on your back, and they look like water wings," Dr. Imber explains. "It's a look that originated when saline implants were still prevalent, and the bag was typically placed under the pectoral muscle rather than layered between the muscle and the breast."

The spherical Hollywood boob has been absorbed by fine art (Lisa Yuskavage's nudes), assimilated into fiberglass mannequins (Ralph Pucci's "Goddess" line), taken up by Marvel Comics (see the latest figurine of Mary Jane, Spider-Man's girlfriend)—and, naturally, adopted by Barbie herself. Maybe it's past time for another remake of One Touch of Venus, the 1948 film in which Ava Gardner played a window dresser's dummy come to life.

Around the same moment that Universal released this Pygmalion-inspired fantasy, Christian Dior—who had just introduced his cinched and buttressed New Look—declared, "Without foundations there can be no fashion." Sixty years later, women can insert their stays, boning, trusses, and padding directly into their own mortal flesh.

The current species of clinically modified breasts and derrières will, inevitably, go out of style—as surely as did the snub noses of 1960s rhinoplasty and last fall's Balenciaga platform heels. Disposing of them will be a process a little more complicated than snipping shoulder pads out of an 80s Alai'a suit jacket or burning a 40s Playtex Living Girdle, a contraption that compressed the posterior into an uncleaved mono-buttock. Heterosexual women are not the only self-mutilators at risk of becoming fashion victims. Also in line for obsolescence are the guys, who, in search of a virile sort of hermaphroditism, have undergone Tom of Finland-like pec implants. ("No sex without pecs," goes one gay mantra.) "Envy of the opposite sex is powerful," notes Dr. Lieberman.

Meanwhile, fashion is on the move again, and so is body-part fixation. "In a split second it's on to the next thing," says Pucci, whose current best-selling female mannequins are "thin, flat-chested, narrow-hipped, and long-legged, ( with good collarbones." Simultaneously, Style.com has named legs, and The New York Times clavicles, the latest erogenous zones. "The bony parts are replacing the sexual areas," says Dr. Lieberman. "If sex is no longer forbidden or mysterious, what kind of charge is there in exposing your pelvis or crack?" At Manhattan black-tie parties, women are giving up their plunging, trailing, siren gowns for abbreviated, child-like dresses, either with a raised waist or no waist at all. "You can attribute those baby-doll looks—and all the dresses over skinny jeans or leggings—to the fashion and celebrity icons who over the last year have been pregnant," suggests Stacey Bendet, designer for the avant-garde label Alice & Olivia.

And that's just about as far from a toned midriff and artificially enlarged knockers as you can get—for now. If anatomy is destiny, as Freud proposed, then it is human nature to try to reshape both. .