It’s a punchline: because they can. Or is it, as the famous (and brilliant?) sociobiologist Desmond Morris explains, because it's in the nature of brilliant men to cheat on their wives.

These powerful men, according to Morris, are "so highly rewarded by society for their achievements that they are unable to limit their curiosity to new problems in their special fields.”

Consequently, "novel sexual experiences … suddenly seem irresistible.

"It is not the mating act itself that is so important -- that varies very little. It is the thrill of the chase and the excitement of a new conquest that drives them on.

Once the conquest has been made, the novelty of the affair soon wears off and another chase is begun. Each illicit episode involves stealth and secrecy, tactics and strategy, and the terrifying risk of discovery, making it the perfect metaphor for the primeval hunt."

Morris concludes that powerful men cheating on their wives' is "sadly, simply a by-product of the human exploratory urge, and one of the prices we -- and wives the world over -- have to pay for being the most innovative species on the planet."

And so there we have man's epochal, expensive storyline.

And so I say to Elin: go shopping, and stop putting out. Then maybe you'll keep him.