There were real reasons that you were attracted to somebody originally. The brain doesn't pick willy-nilly. Unless you part ways hating each other for some reason, that mechanism could get triggered again. You can literally fall in love again.

It certainly would have been adaptive for ancestral man to have a chubby wife during stressful times of famine. Not only would she have had more calories to burn, and thus more energy and endurance, but since fat stores estrogen, she would have remained fertile for longer.

Any kind of novelty or excitement drives up dopamine in the brain, and dopamine is associated with romantic love.

Today, American women bear an average of 2.2 children that live to adulthood. Across most of Europe, women bear even fewer young.

Anthropologists have found evidence of romantic love in 170 societies. They've never found a society that did not have it.

In courtship, who wins and who loses will determine who passes on their DNA to tomorrow.

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.