[Useless]

Along somewhat similar lines, here's an article I read yesterday about why we want sex, and why we want it with more than one mate. It's for the good of the species!

http://www.reuniting.info/science/sex_in_the_brain

The central neurochemical player behind falling in—and out—of love is dopamine. Dopamine is the principal neurochemical that activates your reward circuitry. Your reward circuitry drives nearly all of your behaviors. In other words, most all roads lead to Rome, or to the reward circuitry so you can assess things as "good, bad, or indifferent."

At its most basic, this circuit is activated when you engage in activities that further your survival, or the continuation of your genes. Whether it’s sex, eating, taking risks, achieving goals, or drinking water, all increase dopamine, and dopamine turns on your reward circuitry. You can think of dopamine as the "I’ve got to have it" neurochemical, whatever "it" is. It’s the "craving" signal.

...

Researchers placed electrodes in rats’ reward centers to stimulate them, much as dopamine does. The rats could then press a lever to stimulate the reward center. That’s all those rats did. rat pushing leverThey ignored food, receptive females and their own pups, if female. They just sat there pressing the lever over and over, wasting away…not unlike crack addicts.

Also:

Addiction mechanisms are complex. Yet the one aspect they share is dopamine. All addictive substances and activities increase dopamine. Porn, accumulating money, gaining power over others, gambling, compulsive shopping, video games…if something really boosts your dopamine, then it’s potentially addictive for you. Why did Martha Stewart risk everything for more money? She got a thrill from a stock market gamble. She didn’t need the money; she needed the dopamine.