Why would someone as rich and powerful as Eliot Spitzer put his family, his job and his promising future on the line for an alleged $4,000 date with a prostitute?

Is this pathological or inherent in human nature?

Scientists says it's more likely to be the latter. They attribute this kind of behavior to natural promiscuity combined with opportunity - along with a risk-taking personality common to men like Bill Clinton and John F Kennedy. It's what makes them seek office and what makes us want to vote for them.

Psychologist Christopher Ryan, author of "Sex in Prehistory," says the desire for sex with more than one person has always been there - for leaders and followers alike. "The desire is not a function of status or power - it's a question of availability."

What's relatively new to the human race, he said, is the ability to exercise power and the connection between power and sex.

That's because, for most of human existence, there was only so far a man could coerce others when food was essentially free and hard to hoard. And until relatively recently, sex with multiple partners was the norm. "It would have been very unusual 100,000 years ago for a person to have one sexual partner for 30 years," said Ryan in an interview from Barcelona.

We don't know this for sure, because prehistoric sexual behavior doesn't fossilize, but there's much we can infer from studying how people in foraging cultures live today, he said. Such cultures tend to be relatively egalitarian and promiscuous, at least by American standards, he said. But prostitution is rare, as he believes it was for most of our past.

"There would be no need for prostitutes because there would be very few sexually frustrated men," he said.

So in other words, if Spitzer had been born in 40,000 B.C., he would never have gotten into this fix.

While Ryan argues that men and women are both naturally promiscuous and power simply gives men the opportunity to follow that nature, psychiatrist Gabriela Cort takes a more open view of the human male. Alpha males - leaders - are often indeed full of pent-up sexual energy, but they don't always use it to get in trouble, said Cort, author of the upcoming book, "Leading Under Pressure."

"Some alpha males do whatever they want for their own purposes but others can be very loyal." Alpha males often have excess sexual energy, but instead of cheating or visiting high-priced call girls, she said, many channel it into other pursuits. "Some people create things - or do things for the public good."

Temple University psychologist Frank Farley suggests that while we're busy shaking our heads at Spitzer, we could stand to look back at ourselves and question why we vote for men like him. Risk-taking personalities are attracted to the uncertain world of politics, he said, and at the same time voters are attracted to them.

"We want our leaders to show some qualities of innovation," he said. "We want bold men willing to push their ideas."

We don't choose people riddled with anxieties to run our government or our corporations, though such people may act in a thoughtful, conscientious way. We loved John Kennedy for standing up to the Soviets during the Cuban Missile Crisis.

"We don't want shrinking violets in these kinds of roles," Farley said.

Along with that package you get personal risk-taking - the affairs, the dabbling in solicitation and sometimes other crimes. "It's hard to get rid of it in politics," he said.

The other question that left many of us puzzled: Why pay for it when a man like Spitzer could probably get women for free?

"Men such as those in Spitzer's position do not so much pay for women to have sex with them; they pay for women to go away AFTER having sex with them," said evolutionary psychologist David Buss of the University of Texas. "It's one strategy some men use for minimizing the costs, although obviously it did not work for Spitzer."

Contact staff writer Faye Flam at 215-854-4977 or fflam@phillynews.com.