Tomorrow marks that special day when we celebrate the magic of love. And maybe there is some magic dust involved.

But scientists such as Rutgers University anthropologist Helen Fisher are beginning to realize that love actually is a curious mixture of DNA, brain power and brain chemicals.

Her research reveals that love is a powerful human drive -- perhaps more powerful than people thought. It goes beyond the basic need for companionship and well beyond the desire for sex or procreation.

In truth, love is a drug -- a powerful human desire that can become addictive, dangerous and sometimes deadly.

"I thought it was an emotion or a series of emotions, but we found out that it's a drive," said Dr. Fisher, a member of Rutgers Center for Human Evolutionary Studies. "Wow, romantic love is like hunger or thirst with lots of emotions attached."

It's far more powerful than the desire for sex or companionship. As Dr. Fisher notes, "If you ask someone to go to bed with you, and they say 'no,' you don't kill yourself."

Romantic love can "be stronger than the drive to live," she said. So people sing for love, write love poems, and create myths and legends about love. They become so obsessed with love it can prompt suicide, homicide and even elopement.

"People live for love, kill for love and die for love, and it has evolved that way for very good reason," Dr. Fisher said.

Which defines the mission this Valentine's Eve: How to explain love's vital role in life and survival?

The history of romance traces back to when people began walking on two legs, Dr. Fisher said. Only 3 percent of all mammals are pair-bonding, which means they form long-term relationships mostly to raise and protect their young.

Most of human's closest relatives carry their young on their backs. By the time primitive people were walking upright by 3.5 million years ago, the woman was using her hands to hold her child, which created problems in defending herself and her baby.

It's akin to having a woman hold a bowling ball for four years in one arm while trying to wield a stick for protection in the other, Dr. Fisher said. Children tie up one's hands, so mom had to figure a better means of protection.

What evolved was romance. She needed protection and food, and her male partner saw good reason to protect her and his progeny. Hot romance emerged as the way to cement a relationship that benefited man, woman and child.

In time, love evolved into a powerful drive, much like thirst and hunger, that promoted human survival.

That's not to say people are monogamous forever. Some 43 percent of all couples divorce. The most common time frame -- around four years -- also is based in evolution. By then, the child has survived infancy and no longer requires close care. So it becomes an advantageous time to pursue other partners.

As Dr. Fisher says, the person unconsciously gives in to "the primitive response to create more genetic variety in their young." (Translation: The person sleeps around and produces more babies with more partners.)

Science provides a sound foundation for such conclusions. Magnetic Resonance Imaging of romantic couples' brains showed that love originates in the basal ganglia, near the base of the brain -- also known as the lizard brain -- where the neurotransmitter, dopamine, is produced.

Dopamine sparks a wide range of emotional responses. The base of the brain is the same place that's stimulated by cocaine and other drugs, which result in high energy, novelty-seeking, risk-taking, craving and desire.

Indeed, love acts like a drug.

Relationships can range from loveless sex to monogamy, in which case couples produce oxytocin -- the hormone that encourages people to follow tradition, abide by social norms, respect rules, and be cautious and calm but not fearful.

The 57 percent of all marriages that last generally become more calm and comfortable with intermittent feelings of romantic love, she said.

In her book due out next year, she will divide people into four personality styles based on predominance of brain chemicals involved in love and romance -- dopamine (explorer), serotonin (builder), estrogen (negotiator) and testosterone (director).

She declined to discuss details prior to publication but said it will reveal romantic tendencies and behaviors of people of different biologically-based personalities. She describes it as finding "some of the recipe for romance in love's kitchen."

She also plans to use this science to develop more precise matchmaking tools. She currently is a consultant for the Web site, www.chemistry.com.

Dr. Fisher says MRIs, hormones and brain chemistry still fail to explain the magic of love. Science remains a bit coy. So let's conclude that love is like a piece of cake: It's delicious but can grow stale and even end up smashed in one's face. But tomorrow we emphasize its delicious qualities.

"You can reduce cake to its chemistry," Dr. Fisher said. "But it won't explain the magic of its taste."