The Great Depression of the 1930s saw more American unmarried women working from nine to five, mostly in repetitive, boring, subordinate, dead-end jobs. But the number of working women doubled between 1870 and 1940. During World War II it doubled once again.

Mothers really were not built to raise babies not only by themselves, but with only a partner. For millions of years, a woman had much more than just her husband to help rear her young... This whole idea of 'it takes a village to raise a child' is exactly how we're supposed to live.

Women, it turns out, are built to lead - particularly in the modern world.

A woman of 40 or 50 or 60 can take estrogen replacements, get facelifts, spend her money in bars.

Kissing is not just kissing. It is a major escalation or de-escalation point in a powerful process of mate choice.

What our grandmothers told us about playing hard to get is true. The whole point of the game is to impress and capture. It's not about honesty. Many men and women, when they're playing the courtship game, deceive so they can win. Novelty, excitement and danger drive up dopamine in the brain. And both sexes brag.

Until recently, we regarded love as supernatural. We were willing to study the brain chemistry of fear and depression and anger but not love.