"It's part and parcel of the whole thing about male size and power," says Dr. David D. Gilmore, cultural anthropologist and author of Manhood in the Making: Cultural Concepts of Masculinity. "I mean, look— the big man is attractive to other men and to women. He's admired. Big, strong men stand out, and the penis is a symbol of bigness, of strength, of mastery." In ancient Greece, Gilmore says, a big penis was actually considered vulgar—irrelevant, even detrimental, to the proportional athletic ideal. But it's not uncommon for Mediterranean mothers to kiss their babies' penises and say, "Grow, grow, grow!" And if size weren't the very fulcrum of even the most sophisticated and accomplished male egos, why would F. Scott Fitzgerald ask Hemingway to take a look at his apparently not-so-great Gatsby in the bathroom of the Brasserie l'Escorailles? For that matter, how did a guy like Milton Berle score with Marilyn Monroe?

The answer is unsettling. The title, the diploma, the Raymond Weil. The Danish lingerie model. What are these compared with the ultimate eugenic advantage? Penis size is the final word—the argument ender, the longest straw.

Figures vary, but the generally accepted average length for an erect penis is somewhere between 5 and 5.9 inches. A 2002 study conducted by the International Journal of Impotence Research found that most men seeking penile-lengthening procedures actually have normal-size penises. And, according to the British Journal of Urology International report, while 85 percent of women polled said they were just fine with their partner's size, only 55 percent of the men were satisfied with their own measurements.

Trying to draw a quantifiable link between penis size and the male psyche is a complicated endeavor, which is why scientific research is scant. But Trojan, manufacturer of Magnum-brand condoms, has been filling in the gaps—conducting studies to determine the psychology of its ostensibly more gifted clientele. "They claim to be very spontaneous and very assertive," says Trojan's vice president of marketing, Jim Daniels.

But Daniels divulges a potentially devastating secret: The Magnum isn't any larger than Trojan's other condoms. Its comfortable fit is due to an innovative "baseball bat" shape. The length and circumference are identical to those of other lines. Only the XL variety is larger—by 30 percent—and that's only required by about 6 percent of the male population. "You've got the image of the package—it's premium; it's gold foil," Daniels says. "And what guy doesn't want to think that he can handle a Magnum condom? There's a certain machismo involved."

Sound familiar? It should. Because human behavior will always be subject to the same social dynamics that played out at elementary-school—and penis size is no exception. Short men have Napoleon complexes. Coworkers still ridicule each other about their shirts. And successful young businessmen aren't above shoving it in your face—sometimes literally. Take G.C., for instance, a 31-year-old New Yorker who works in finance who taunted his pals one night after a few too many drinks by pressing his 8 1/4-inch member against the window outside a house party in the Hamptons—and knocking on the glass to get the partygoers' attention.