For one species of flatworm that lives in the gills of freshwater fish, monogamy is the rule. But for humans and every other living creature, biologists believe nature prefers that man and beast have multiple sexual partners.
With that in mind, some biologists say we shouldn’t be too surprised when public figures like former New York Gov. Eliot Spitzer and others get caught cheating on their mates.
We may just be wired that way.
“Nature wants one thing, and what it wants are babies,” Jeffrey Kluger, TIME magazine’s science editor, told TODAY’s Meredith Vieira on Wednesday. “It also wants lots of them and it wants variety, because the greater the genetic variety, the greater the likelihood that the babies are going to survive to adulthood and do well. So even when we’ve had children, we have some very primal software that keeps telling us, ‘Look around.’ ”
Once upon a time, biologists thought that there were a number of animals — eagles, geese and beavers among them — that remained monogamous throughout their lives. But DNA testing has shown that even the animals that look like the models of fidelity are getting out at night for a little extra on the side. And, according to a report filed by TODAY’s Natalie Morales, the list of officially monogamous creatures is down to one — that freshwater flatworm that physically attaches itself to a mate for life.
“Men will look for women who look like they’re young and fecund,” Kluger added. “And women look for men who look like they’re good providers, which is why rich and powerful men do well.”
Even in human societies, Americans are relatively unique in their expectation of lifelong fidelity, said University of Texas psychologist and author David Buss.
“Historically, most cultures are polygynous, meaning men are legally entitled to take multiple wives, and so mating with many women is very common across cultures and perfectly acceptable in many cultures,” he said from Austin, Texas. “Our culture is somewhat unique in that we have presumptive monogamy or legal monogamy — men are only supposed to have one woman.”
Vieira wondered whether we haven’t evolved beyond our biological impulses, and both men agreed that humans do have the ability to override their genetic and biological programming. And, studies show, most people do, with 65 percent of men and 75 percent of women claiming that they have never cheated on their spouses.
“If you look at marriages, in fact, more than half of them — in America anyway — do remain monogamous,” Buss said. “I think it’s important to keep in mind that although we do have these biological impulses to stray, we also have inhibitions against straying, for example, reputational damage. When people get caught straying, they incur reputational damage, and we are very concerned about our social reputations.”
The conflict between desire and morality was famously defined by former President Jimmy Carter, who told Playboy that he felt “lust” in his heart, and was roundly criticized for admitting even that.
- Amy Robach on Cancer Fight: 'I'm in the Thick of It'
- Teen Son Charged with Fatally Shooting Parents in Capistrano Mansion
- Woman Who Drove Children into Ocean Charged with Attempted Murder
- MasterChef Judge Graham Elliot Loses Nearly 150 Lbs. - See His Transformation
- It'll Be a Girl for Eva Amurri Martino
But, Buss said, Carter was making an important point. “It’s a reflection of reality,” he said. “I think it’s also important to keep in mind that both men and women experience lust in their hearts. They feel attractions to others.”
Both scientists agreed that while women do cheat, men are more likely to.
“There are two reasons for that,” Kluger said. “First of all, men simply can breed more. Men biologically can conceive a child every day if they wanted to. So we’re trip-wired for that kind of thing.”
Above the rules?
The way society is structured also adds to a male’s incentive to cheat. “We still live in a patriarchal society, which means men are more commonly in positions of power,” Kluger went on. “Positions of power tend to validate the belief that you’re above the rules. You and I don’t get a motorcade when we go places. We don’t get a flying wedge on the sidewalk. So if you’re entitled to the sidewalk and you’re entitled to the street, why aren’t you entitled to that beautiful woman on your communications staff?”
Buss said that although the urge to cheat is universal, people with certain personality traits are more likely to stray than others.
“Our studies find two in particular,” said Buss in addressing those traits. “One is impulsivity or lack of conscientiousness. But the most important personality characteristic is narcissism. Men who are high on the narcissism personality characteristic are more likely to cheat than men who are lower. They put their own needs and their own urges before those of their families.”
Both agreed that “biology made me do it” isn’t an excuse for infidelity.
“We have to be realistic about our human nature. We have these impulses to stray,” said Buss. “But we also have inhibitions against straying and the ability to choose whether or not we do.”
© 2013 NBCNews.com Reprints