by Dr. Sharon Moalem (HarperCollins Canada)

How Monogamy Works

There are over 6 billion people on the planet. Why do we pick just one and spend an entire lifetime with him or her?

Why do we need sex? Looking back into our evolutionary past, Dr. Sharon Moalem explores the ways in which the struggle to survive and create healthy offspring has determined -- and continues to determine -- our sexuality. From ground-breaking research to strange and fascinating discoveries to an exploration of the roles of culture, biology, and time on sexuality, How Sex Works is an entertaining and comprehensive history of sex that goes far beyond our classic "birds and bees" approach.

I'm so excited and I just can't hide it

Millions of words -- in books and on blogs, in magazine articles and advice columns -- have been written about mastering the search for Ms. or Mr. Right. And millions of people have wondered why they keep dating the wrong man or woman when they think they know what's really good for them. They think they know what they need; the problem is, what they need isn't always what they want.

So why do we want what we want anyway? How much of what turns us on is hardwired?

Like everything else, attraction and arousal (and possibly love, for that matter) are the products of millions of years of finely tuned biological engineering. And there's really only one goal behind the engineering -- to get you to have sex.

As you'll see, much of what we are pre-programmed to find attractive may be connected to what it tells us about health, fertility, and compatibility of potential mates. Genetic compatibility, that is. Nature isn't really concerned about similar political views or favorite movies, although it does place stock in appearances. From the standpoint of survival, in some sense it really cares that we have strong offspring, and that they get what they need to grow up and give us grandkids in turn. But genetic compatibility only gets us halfway there in terms of successful offspring -- it can give us healthy babies, but those babies need parents to protect and nurture them into maturity. And that's where love comes in. Falling and staying in love -- the pair bonding that keeps a couple together long enough to have, raise, and care for children -- almost certainly involves chemical processes that are a product of millions of years of evolution.

A new study published in March 2008 in the journal Evolution and Human Behavior shows that being in love with someone actually works to dampen the sexual appeal of people of the opposite sex that we might otherwise find attractive. In another study, Florida State University researcher Jon Maner took two groups of heterosexual college students who "were currently in a committed romantic relationship" and showed them rapid-fire bursts of images depicting very attractive and average-looking men and women. Before watching the images, each group wrote essays. The first group of students watched the images after writing essays about extreme happiness. The second group wrote essays about moments when they felt extreme love toward their partners. In the group that was primed by writing about happiness, the participants in the study seemed to pay about the same attention to attractive people and average people. But in the group that wrote essays about moments of extreme love towards their partners, their attention, in the words of the researchers, "was captured substantially less by attractive alternatives than by other targets." The researchers' theory is that concentrating on the love you have for your partner may block the normal reflexes that might otherwise cause you to consider other potential "attractive" partners. This may be a mechanism that evolved to keep couples together. If you keep seeking alternatives to your partner, the likelihood of building a lasting and successful relationship, especially one that leaves you with children, diminishes.