When chimps threaten, they open their mouth and show their teeth. It's a little like waving a knife in front of you. It's very primitive, and therefore bizarre.

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.

The only people you and I are likely to know in common are people in the news - politicians, journalists and celebrities.

As women in industrial societies join the paid workforce, they gain the economic means to depart unhappy marriages more easily.

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.

People have often asked me whether what I know about love has spoiled it for me. And I just simply say, 'Hardly.' You can know every single ingredient in a piece of chocolate cake, and then when you sit down and eat that cake, you can still feel that joy.

At first I assumed hate was the opposite of love. But it isn't. The opposite of love is indifference.