Exactly how do we signal our amorous interest and intent in each other? It's been trivialized, even demonized, but the coquettish behavior indulged in by men and women alike is actually a vital silent language exchanging critical-and startling-information about our general health and reproductive fitness.

"She was," he proclaimed, "so extraordinarily beautiful that I nearly laughed out loud. She... [was] famine, fire, destruction and plague... the only true begetter. Her breasts were apocalyptic, they would topple empires before they withered... her body was a miracle of construction... She was unquestionably gorgeous. She was lavish. She was a dark, unyielding largesse. She was, in short, too bloody much... Those huge violet blue eyes... had an odd glint... Aeons passed, civilizations came and went while these cosmic headlights examined my flawed personality. Every pockmark on my face became a crater of the moon."

So Richard Burton described his first sight of a 19-year-old Elizabeth Taylor. He didn't record what happened next, but a growing cadre of scientists would bet their lab coats and research budgets that sometime after that breath-catching, gut-gripping moment of instant mutual awareness, Liz tossed her hair, swayed her hips, arched her feet, giggled, gazed wide-eyed, flicked her tongue over her lips and extended that apocalyptic chest, and that Dick, for his part, arched his back, stretched his pecs, imperceptibly swayed his pelvis in a tame Elvis performance, swaggered, laughed loudly, tugged his tie and clasped the back of his neck, which had the thoroughly engaging effect of stiffening his stance and puffing his chest.

What eventually got these two strangers from across the fabled crowded room to each other's side was what does it for all of us-in a word, flirtation, the capacity to automatically turn our actions into sexual semaphores signaling interest in the opposite sex as predictably and instinctively as peacocks tan their tails, codfish thrust their pelvic fins or mice twitch their noses and tilt their backs to draw in the object of their attention.

Long trivialized and even demonized, flirtation is gaining new respectability thanks to a spate of provocative studies of animal and human behavior in many parts of the world. The capacity of men and women to flirt and to be receptive to flirting turns out to be a remarkable set of behaviors embedded deep in our psyches. Every come-hither look sent and every sidelong glance received are mutually understood signals of such transcendent history and beguiling sophistication that only now are they beginning to yield clues to the psychological and biological wisdom they encode.

This much is clear so far: flirting is nature's solution to the problem every creature faces in a world full of potential mates-how to choose the right one. We all need a partner who is not merely fertile but genetically different as well as healthy enough to promise viable offspring, provide some kind of help in the hard job of parenting and offer some social compatibility.

Our animal and human ancestors needed a means of quickly and safely judging the value of potential mates without "going all the way" and risking pregnancy with every possible candidate they encountered. Flirting achieved that end, offering a relatively risk-free set of signals with which to sample the field, try out sexual wares and exchange vital information about candidates' general health and reproductive fitness.

• Free Brochures
• Books
• Education
• Health & Lifestyle