When you fight, anger drives up testosterone in both men and women.

You know, when you've been dumped, the one thing you love to do is just forget about this human being, and then go on with your life - but no, you just love them harder.

Overdone lipstick is a deterrent to men. It rubs off easily onto their skin and the edges of their shirts, so it discourages them from kissing, touching, and coming closer to you, which is what they really want to do!

Women like signs of money and education - things that indicate that not only is this guy going to have some resources, but he's also willing to share them.

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.

We're apt to fall in love with those who are mysterious and challenging to us.

I think romantic love evolved to enable you to focus your mating energy on just one individual at a time, thereby conserving mating time and energy.