Language is a window into human nature, but it is also a fistula, an open wound through which we're exposed to an infectious world.

Evolutionary psychology is one of four sciences that are bringing human nature back into the picture.

The supposedly immaterial soul, we now know, can be bisected with a knife, altered by chemicals, started or stopped by electricity, and extinguished by a sharp blow or by insufficient oxygen.

You could think of an ecosystem as a bunch of antagonistic arms races, almost: Everything that an animal depends upon for food is the body part of some other animal or plant who would just as soon keep that body part for itself.

The reason the United States is not so likely to invade Iran is precisely because of the lessons learned from Iraq. And conversely, the Iranian push towards nuclear capability is calculated to deter invasions like the kind deposing Saddam Husain.

The brain is not a bag of traits. It's startlingly complex. There are few or no single genes with a consistent effect on the mind.

The problem with the emotions is not that they are untamed forces or vestiges of our animal past; it is that they were designed to propagate copies of the genes that built them rather than to promote happiness, wisdom, or moral values.