Apparently, everyone’s doing it. Bill was doing Monica. Arnie was doing the housekeeper. Tiger was doing pretty much anything with a pulse. According to Eric Anderson, sociologist and author of The Monogamy Gap, a more mature, honest society would simply drop the pretence that monogamy is either realistic or desirable.

“Society says that people are meant to be faithful to their partners,” Anderson explains. “That’s the expectation of people in relationships at a very young age but everyone is running around cheating. Everyone comes to realise it. And the approach of stigmatising it and hyper-moralising about it, the approach that men should just keep their dicks in their pants, it isn’t working.”

This is, in effect, the ‘monogamy gap’ referred to in Anderson’s book, in which he interviewed young men in relationships to assess both the prevalence of infidelity and their motivations for cheating.

“A lot of men, when they enter a relationship, they want to be faithful – they don’t want to be that guy who cheated – but they also think they’ll have long, exciting sex lives with that partner,” Anderson explains. “But it often doesn’t work out that way. Often, the longer they’re with that partner, the more they love them but, at the same time, the more they come to desire sex with someone else recreationally.”

Anderson’s conclusion is that monogamy forces people – not just men – into contradiction, where they want what they are conditioned not to want. He argues, perhaps provocatively, that cheating on a partner without ending the relationship is in fact an affirmation of love.

“There’s this belief that if a man cheats on his wife or girlfriend, it either means she hasn’t provided enough sexual fulfilment – which is a horrible thing to say to a woman – or that the guy is looking for fulfilment elsewhere,” Anderson says. “But I spoke to these young men who weren’t forced to stay with their partners – they had no financial or formal obligation to stay with them and they told me, ‘I just want sex with someone else’. In a weird way, it’s a symbol of their love for their partner that they want to keep the relationship, but just want sex with another person.

“The prevailing message is that if men cheat on their partners, they’re either scum or they don’t love the woman they’re with. Between those messages and my message, which is that men just want sex with someone else, which is healthier? In that argument, it’s the expectation of monogamy that’s unhealthy.”

Anderson’s focus on men has been seized upon by some detractors as inherently anti-woman, as license for men to cheat on their wives or girlfriends by invoking “biological urges” as a get-out-of-jail-free card. But he is quick to insist that his conclusions apply equally to women – men are merely the focus because male behaviour is his area of speciality.

“Monogamy also fails women,” he insists. “Academic feminists have been saying for years that marriage introduces power and patriarchy into a relationship. And while monogamy might serve some men well, particularly those with low sex drives, it doesn’t come naturally. It’s a social expectation. If it came naturally, we wouldn’t have to talk about it all the time.”

Traditionalists, of course, will interpret Anderson’s anything-goes approach as yet another attack on the besieged definition of marriage as a union between one man and one woman. Anderson, for his part, is not anti-marriage – he is, though, prepared to question what marriage means.

“Marriage doesn’t have to imply sexual fidelity – the concept of marriage means you’re devoted, but that doesn’t have to mean sexual exclusivity,” he says.

“Many stigmas of sexuality have dropped away. You’ve now got a hook-up culture where people can go and meet someone in a club. Oral sex and anal sex used to be completely taboo but aren’t any more. One stigma that has remained, though, is against open relationships.

“Why do we consider monogamy moral? Why can’t open relationships be considered moral?”

Resistance to Anderson’s theories runs deep among those committed to preserving marriage – defined as being between one man and one woman – as the bedrock of society.

“Successful civilisations have had that union between a man and a woman at their core,” argues Alistair Thompson, spokesman for the UK’s Coalition For Marriage, a grassroots organisation that lobbies on behalf of conventional marriage. “To suggest it’s desirable to have polygamy or open relationships is risible. All the statistics show the life chances of children are dramatically improved by stable family units – they do better at school, they have greater life expectancy, they form more stable relationships, they are less likely to become caught up in the criminal justice system. Hard-wired into humans is the importance of relationships and stability.

“So I fundamenally disagree that monogamy is a bad thing. For an academic to publish a book like this – it just sounds like a charter for philanderers. I think we’ve come a long way from when it was just about bonking everything that moved.”

Wonder what Tiger, Bill and Arnie think about that.