Romantic love allows you to focus mating energy. Attachment sustains that relationship as long as necessary to raise your baby.

If we remained perpetually infatuated, we couldn't eat, sleep or work.

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

Men tend to be hierarchical, but women are driven to make lateral connections so they can cooperate.

We all have restlessness in long-term relationships.

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.

Women have a better sense of smell than men do, and it's even sharper in the middle of their menstrual cycle, when estrogen levels peak and women are more likely to be deciding whether a man's attractive.