Jealousy can even be good for love. One partner may feel secretly flattered when the other is mildly jealous. And catching someone flirting with your beloved can spark the kind of lust and romance that reignites a relationship.

People have often asked me whether what I know about love has spoiled it for me. And I just simply say, 'Hardly.' You can know every single ingredient in a piece of chocolate cake, and then when you sit down and eat that cake, you can still feel that joy.

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.

Romantic love is one of the most addictive substances on Earth.

Neither gender is routinely more jealous - although women are more willing to work to win back a lover, while men tend to flaunt their money and status and are more likely to walk out to protect their self-esteem or save face.

Real competition can drive up testosterone, which boosts libido.

Along with our many human propensities, we evolved a huge cerebral cortex with which we make decisions.