According to biologists, having multiple sexual partners is normal in fact, nature prefers it that way.
Blame it on biology
Biologists once believed there were a number of animals, such as eagles, geese and beavers, that were monogamous, but the list of monogamous creatures has dwindled to one the freshwater flatworm, which physically attaches itself to a mate for life. A little extreme perhaps, but if that's what you've got to do to make sure your partner doesn't stray…
Monogamous or polygamous?
University of Texas, psychologist and author David Buss says, "Historically, most cultures are polygamous, meaning men are legally entitled to take multiple wives. Our culture is somewhat unique in that we have presumptive monogamy or legal monogamy men are only supposed to have one woman" [and vice versa].
To stray or not to stray
It seems humans have the ability to override their genetic and biological programming towards polygamy. And studies show that most people do, with 65 percent of men and 75 percent of women claiming they have never cheated on their partner.
Buss says, "Although we have these biological impulses to stray, we also have inhibitions against straying [because] when people get caught straying, they incur reputational damage and we are very concerned about our social reputations."
Buss and Time magazine science editor Jeffrey Kluger agree that while women do cheat, men are more likely to.
"There are two reasons for this," says Kluger. "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."
Kluger adds that society is still structured in ways that encourage men to cheat. "We still live in a patriarchal society, which means men are more commonly in positions of power. Positions of power tend to validate the belief that you're above the rules."
Spotting a cheater
Want to find out if your partner is monogamous or polygamous? It's easy. Buss says that while the urge to cheat is universal, there are some personality types that are more likely to stray than others.
"Our studies find two in particular," says Buss. "One is impulsivity or lack of conscience, but the most important characteristic is narcissism. Men who put their own needs and their own urges before those of their families are more likely to cheat."