"Daily Mail" columnist Liz Jones is at it again -- this time she's tsk-tsking celeb cads like David Arquette, Jude Law and Tiger Woods for stepping out on their beautiful, powerful partners with -- gasp! -- waitresses. Jones calls the phenomenon "cheating down."

Let's ignore Jones's not-at-all subtle classism for a minute -- servers are human beings with legitimate careers and not, you know, Victorian prostitutes -- and explore her point about the appeal of sleeping with someone, er, "below your station."

She surmises that dudes like Arquette step out on their Courteney Coxes to sleep with women like Jasmine Waltz (the server he claims to have gotten on) because they love it when a woman acts grateful to bang them.

We wanted to know if there was a more cultural reason for "cheating down," so we asked Helen E. Fisher, PhD, a biological anthropologist at Rutgers University. Dr. Fisher's research examines the role the brain plays in love and relationships, and she's the chief scientific adviser for dating site Chemistry.com.

According to Dr. Fisher, these pairings are a perfect storm of a woman wanting to marry up and men wanting to feel powerful.

"Men with a lot of money attract a woman like that," she said. Cocktail waitresses and their ilk are just trying to commit hypergamy, which is the fancy, book-learnin' term for "marrying up."

They are attracted to powerful men and, consequently, men are attracted to them for several reasons, including because a woman who's less powerful is a safe bet for cheating because she is outside the powerful circles the man -- and his wife -- run in. "If a man goes down the ladder to cheat, he can impress [his mistress] with his money, class and background," Dr. Fisher said.

Another reason a man might be attracted to someone of a lower class may be because he comes from that kind of background as well. (Think of "30 Rock"'s Jack Donaghy and his affair with his childhood sweetheart.) There's comfort in the familiar.

There's a novelty factor for guys as well. "Sometimes men want to take a walk on the wild side," she said. "The novelty drives up the dopamine in the brain and that makes them feel sexy. Also a 'lower' person will adore them, unlike an equal, and they like to feel adored."

This makes us uncomfortable.

Dr. Fisher also explained that, conversely, powerful women are attracted to powerful men because there's an exchange involved. She may have money, but he may have notoriety. (Although, in Cox and Arquette's case, it seems like he's the one who was marrying up.) Long story short, it's all about fulfilling one's needs.

Makes sense. Except that we're pretty sure these guys would have slept with a female prime minister if she was hot. (Even if she was off-hot.) Heck, it's not like we haven't gone after a chimney sweep or two in our day. We're not above sex outside of our station, because we're just that culturally advanced.