That "ol' black magic" is a fickle force. The chemistry of romantic love can trigger the chemistry of sexual desire and the fuel of sexual desire can trigger the fuel of romance. This is why it is dangerous to copulate with someone with whom you don't wish to become involved. Although you intend to have casual sex, you might just fall in love.

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.

I think that property is very important in this day and age. It defines you; you worked hard to get it. It's meaningful to you, and when you divorce, a lot of people have a lot of battles over their property for good reasons.

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.

Men are so visual, they see a woman who appeals to them physically, and it will trigger the romantic love system faster.

There exists no culture in which adultery is unknown, no cultural device or code that extinguishes philandering.

I don’t think we’re an animal that was built to be happy; we are an animal that was built to reproduce.