What our grandmothers told us about playing hard to get is true. The whole point of the game is to impress and capture. It's not about honesty. Many men and women, when they're playing the courtship game, deceive so they can win. Novelty, excitement and danger drive up dopamine in the brain. And both sexes brag.

People live for love. They kill for love. They die for love. They have songs, poems, novels, sculptures, paintings, myths, legends. It's one of the most powerful brain systems on Earth for both great joy and great sorrow.

Real competition can drive up testosterone, which boosts libido.

Hair that gleams can send a clear sign that you're young and in your prime, whatever your actual age.

Of all the foods we share, there is nothing more primordial than meat. It's no surprise that meat-eaters still want a partner who will give, receive and share this primordial symbol of a budding partnership.

From my studies of genetics and neuroscience I have come to believe that people fall into four broad personality types - each influenced by a different brain chemical: I call them the Explorer, Builder, Director, and Negotiator.

Sometimes we fall in love with somebody who will probably never love us, for reasons having nothing to do with us but with their own mindset, their chemistry.