If two very different people pool their DNA, they'll create more genetic variety, and their young will come to the job of parenting with a wider array of skills.

Men couldn't care less if your strands are perfectly styled and neat. In fact, he might like you more with some wildness or bedhead, since it shows you're carefree and relaxed.

A hundred years ago, if you had a child out of marriage, you'd be a social disgrace. Today women feel comfortable enough economically and culturally to bring up a child without a recognized commitment from a man.

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.

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

A world without love is a deadly place.

Games are the way we keep romance alive. They're based in human hardwiring. Playing hard-to-get or leaving a little to the imagination allows the woman to be wooed and appreciated and the man to be challenged and intrigued.