The Red Queen: Sex and the Evolution of Human Nature

by Matt Ridley

There is a cautionary tale that scientists tell one another about a man who cuts the legs off a flea to test his theory that fleas’ ears are on their legs. He then tells the flea to jump and it does not, so he concludes that he was right; fleas’ ears are in their legs.

This is a paradox. It can be resolved in one of three ways. We can blame adultery on men, asserting that the persuasive powers of seducers will always win some hearts, even the most reluctant. Call this the “Dangerous Liaisons” explanation. Or we can blame it on modern society and say that the frustrations and complexities of modern life, of unhappy marriages and so on, have upset the natural pattern and introduced an alien habit into human females. Call this the “Dallas” explanation. Or we can suggest that there is some valid biological reason for seeking sex outside marriage without abandoning the marriage—some instinct in women not to deny themselves the option of a sexual “plan B” when plan A does not work out so well. Call this the “Emma Bovary” strategy.