Things were not looking good for Josh (not his real name). He had lost all the money he'd made as a day trader. To make matters worse, his longtime girlfriend walked out on him, taking all the furniture and whatever else she could carry. By any measure, it was rock bottom. But when Josh's friends mobilized the rescue crew, they were astounded: Josh appeared to be totally unfazed.

"He didn't care!" says Josh's best friend, Steve (not his real name), a 35-year-old hedge-fund manager who worked with him on Wall Street. "He shrugged it off. It would have killed a lesser man." But Steve knew his friend's nonchalance wasn't due to some elaborate form of self-hypnosis or handfuls of Wellbutrin. Josh owed his composure to something far simpler: nine inches of the most primal form of self-assurance known to man.

"If it weren't for his cock, he'd be a hobo riding the trains around the country," Steve says. "It's opened doors for him. Rich women put him up at their apartments. We have friends who have more money than him and are more successful than him, but they all say, 'I want to come back as this guy.' Secretly, we all want to be him."

Does it really come down to this? Millions of years of evolution culminating in a highly advanced society whose members are adept at evaluating worth on the basis of intelligence, compassion, creativity—or even money—and it turns out our core psychology is still governed by the length of our reproductive organs?

"Are you kidding me?" says Josh (who's 33 now and has started over as a physical therapist). "That's basically my philosophy on life! Whenever it gets bad, I'm like, 'Hey, I got the one good thing!' My ex-girlfriend called it BDS—Big Dick Syndrome. It was hard to even have an argument, because I'd just be like, 'Whatever.' It's an ego thing. Because when it comes down to men, I mean, really, what else is there?"

This is obviously not a popular notion among sex therapists, who tend to be of the opinion that "it's what you do with it that counts." But such reassurances are all but inaudible amid the phallocentric babble that permeates our post—Sex and the City dating landscape.

"Size matters only if you let it matter," says psychologist and advice columnist Dr. Joyce Brothers. The thing is, a lot of us are letting it matter—and not just within the confines of the bedroom but as the unspoken arbiter of our confidence. It turns out we've been doing this for a very long time. According to a 2006 report by the British Journal of Urology International, there is evidence that "prehistoric cave dwellers attributed the symbolic values of strength and power to penile size, as well as those of virility and fertility." And some anthropological-minded observers confirm what none of us likely want to hear—that Josh isn't lost in some fun-house mirror-land of his own personal delusion. He's enjoying the satisfaction that comes from living in a world that has made him its king.