The Right Chemistry

Evolutionary roots, brain imprints, biological secretions. That's the story of love.

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If, in nature's design, romantic love is not eternal, neither is it exclusive. Less than 5% of mammals form rigorously faithful pairs. From the earliest days, contends Fisher, the human pattern has been "monogamy with clandestine adultery." Occasional flings upped the chances that new combinations of genes would be passed on to the next generation. Men who sought new partners had more children. Contrary to common assumptions, women were just as likely to stray. "As long as prehistoric females were secretive about their extramarital affairs," argues Fisher, "they could garner extra resources, life insurance, better genes and more varied DNA for their biological futures. Hence those who sneaked into the bushes with secret lovers lived on -- unconsciously passing on through the centuries whatever it is in the female spirit that motivates modern women to philander."

Love is a romantic designation for a most ordinary biological -- or, shall we say, chemical? -- process. A lot of nonsense is talked and written about it.

-- Greta Garbo to Melvyn Douglas in Ninotchka

Lovers often claim that they feel as if they are being swept away. They're not mistaken; they are literally flooded by chemicals, research suggests. A meeting of eyes, a touch of hands or a whiff of scent sets off a flood that starts in the brain and races along the nerves and through the blood. The results are familiar: flushed skin, sweaty palms, heavy breathing. If love looks suspiciously like stress, the reason is simple: the chemical pathways are identical.

Above all, there is the sheer euphoria of falling in love -- a not-so- surprising reaction, considering that many of the substances swamping the newly smitten are chemical cousins of amphetamines. They include dopamine, norepinephrine and especially phenylethylamine (PEA). Cole Porter knew what he was talking about when he wrote "I get a kick out of you." "Love is a natural high," observes Anthony Walsh, author of The Science of Love: Understanding Love and Its Effects on Mind and Body. "PEA gives you that silly smile that you flash at strangers. When we meet someone who is attractive to us, the whistle blows at the PEA factory."

But phenylethylamine highs don't last forever, a fact that lends support to arguments that passionate romantic love is short-lived. As with any amphetamine, the body builds up a tolerance to PEA; thus it takes more and more of the substance to produce love's special kick. After two to three years, the body simply can't crank up the needed amount of PEA. And chewing on chocolate doesn't help, despite popular belief. The candy is high in PEA, but it fails to boost the body's supply.

Fizzling chemicals spell the end of delirious passion; for many people that marks the end of the liaison as well. It is particularly true for those whom Dr. Michael Liebowitz of the New York State Psychiatric Institute terms "attraction junkies." They crave the intoxication of falling in love so much that they move frantically from affair to affair just as soon as the first rush of infatuation fades.

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