Security 'bad news for sex drive' :: BBC

The argument is that the female's sex drive is high early in a relationship in order to cement a relationship. Later in the relationship it drops. Here's the argument why:

Dr Dietrich Klusmann, lead author of the study and a psychologist from Hamburg-Eppendorf University, believed the differences were down to human evolution.

He said: "For men, a good reason their sexual motivation to remain constant would be to guard against being cuckolded by another male."

But women, he said, have evolved to have a high sex drive when they are initially in a relationship in order to form a "pair bond" with their partner.

But, once this bond is sealed a woman's sexual appetite declines, he added.

He said animal behaviour studies suggest this could be because females may be diverting their sexual interest towards other men, in order to secure the best combinations of genetic material for their offspring.

Or, he said, this could be because limiting sex may boost their partner's interest in it.

Huh? You've already established the cause of why he's already interested in it.

Then there's an attempt at a supply and demand analogy:

Professor George Fieldman, an evolutionary psychologist from Buckinghamshire Chilterns University College, said: "These findings seem to fit in with anecdotal studies and his explanations seem plausible.

"The rational for why a woman's sex drive declines may be down to supply and demand. If something is in infinite supply, the perceived value would drop."

Hmm. Maybe the idea is if you don't give it way you can sell it for something. Like doing a bit of housecleaning or childcare? Or some tenderness?:

About 90% of women wanted tenderness, regardless of how long they had been in a relationship, but only 25% of men who had been in a relationship for 10 years said they were still seeking tenderness from their partner.

In Why We Love: The Nature and Chemistry of Romantic Love the author, Helen Fisher, writes:

There is a great deal of anecdotal evidence for this negative chemical relationship between attachment and romantic love. People around the world say the exhilaration of romance wanes as their marriage or partnership becomes increasingly stable, comfortable, and secure. Some even go to psychiatrists or marriage counselors to try to renew romantic passion in their relationship. Some seek romance outside their marriage instead. Some divorce. And many settle into a long-term partnership of devoid of romantic bliss.