Like the early days of the Internet, the dawn of personal genomics promises benefits and pitfalls that no one can foresee.

Cognitive psychology has shown that the mind best understands facts when they are woven into a conceptual fabric, such as a narrative, mental map, or intuitive theory. Disconnected facts in the mind are like unlinked pages on the Web: They might as well not exist.

Commerce, trade and exchange make other people more valuable alive than dead, and mean that people try to anticipate what the other guy needs and wants. It engages the mechanisms of reciprocal altruism, as the evolutionary biologists call it, as opposed to raw dominance.

People have long assumed that violence is necessary for political change. Rulers never cede power voluntarily, the argument goes, so progressives have no choice but to contemplate the use of force to bring about a better world, mindful of the trade-off between a small amount of violence now and acceptance of an unjust status quo indefinitely.

There's a common criticism of evolutionary psychology that it's fatalistic and it dooms us to eternal strife, 'Why even try to work toward peace if we're just bloody killer apes and violence is in our genes?'

America had, for one thing, lived in anarchy for - until much more recently than Europe. We had the Wild West, where the cliche of the cowboy movies was the nearest sheriff is 90 miles away, and so you had to pack a gun and defend yourself.

We are visual creatures. Visual things stay put, whereas sounds fade.