Both sexes like the exercise and challenge of sports, but for men it's also a basic display behavior for impressing and winning a mate.

Women apparently are quite drawn to men who have differences rather than similarities in their histocompatibility system. They pick it up by smell, and they can pick it up from kissing.

Falling in love was not really a choice; it just struck me.

Like most animals, we're wired to associate height with power.

There's a lot of talk about the positive aspects of love. We as a society downplay the danger, the anxiety, and the disappointment. We romanticize romance.

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.

We evolved in a tropical climate where the smells of plants and flowers were all around us. We spent a lot of time in the trees with a lot of sunlight and no clothes.