Last week, General David Petraeus resigned from his post as the CIA director, because of an admitted extramarital affair with his biographer Paula Broadwell. Petraeus was a popular figure in the Republican party and in the United States as a whole, especially for his role in transforming combat in the war in Afghanistan. Many had wanted him to run for President. His high-profile position meant that he needed to make sure that he was never vulnerable to blackmail. The affair naturally begs the question: why would the four-star general risk everything to cheat?

Petraeus was, after all, not just a prominent figure in Washington and in the Republican party. He had been married for 38 years. But Petraeus is hardly the first prominent figure in Washington, DC to have cheated on his wife - and often, the press and the public looked the other way. President Dwight D. Eisenhower, a former general, was rumored to have had an affair with the woman who served as his chauffeur in World War II. Another famous World War II general, George Patton, had an affair with his wife's step-niece. General Douglas MacArthur had a mistress, Isabel Rosario Cooper, from the Philippines. A study from last year found that veterans were about twice as likely as civilians to cheat on their spouses.

Baruch Fischhoff suggested to LiveScience that military men like General Petraeus, or other people with high-risk careers, become desensitized to risk after a while. "People tend to underestimate how quickly small risks mount up," Fischhoff said. "You do something once and you get away with it - certain things you're probably going to get away with - but you keep doing them often enough, eventually the risk gets pretty high." Indeed, risk-taking was probably something that Petraeus and Broadwell shared; Broadwell, a graduate of West Point and a lieutenant colonel in the United States Army Reserves, described herself and her husband as "adventure junkies" in an interview with the Charlotte Observer.

Studies also suggest that men become more likely to take risks if they see an attractive woman. A 2008 study asked men to play blackjack after seeing faces of women. Men who saw faces of attractive women were more likely to take risks than men who saw faces of unattractive women.

That is not the only study that claims that women cloud men's judgment. A study from earlier this year found that, when men simply thought that they would interact with women, men's cognitive ability was compromised.

Some experts say that the affair would have actually been a demonstration of "mating intelligence". While losing his career and marriage may seem like horrible risks, they would have seemed like nothing compared to the evolutionary need to reproduce.

"These individuals have these very high-power, high status-positions and the whole idea behind why people might be motivated to get these positions is because it gives them better access to resources that could be used to increase their reproductive success and attract more mates," said Michael Baker, currently a professor at Eastern Carolina University and one of the researchers behind the blackjack study.

Of course, the affair may have simply been a consequence of humans' problems with monogamy. Monogamy is, after all, a relatively new concept in the timeline of human civilization. Temple University psychologist Frank Farley points out that humans are still working out the kinks.