To science we owe dramatic changes in our smug self-image. Astronomy taught us that our Earth is not the center of the universe, but merely one of nine planets circling one of billions of stars. From biology we learned that humans were not specially created by God but evolved along with tens of millions of other species.

Much of human history has consisted of unequal conflicts between the haves and the have-nots.

Measles and TB evolved from diseases of our cattle, influenza from a disease of pigs, and smallpox possibly from a disease of camels. The Americas had very few native domesticated animal species from which humans could acquire such diseases.

Take air quality in the United States today: It's about 30 percent better than it was 25 years ago, even though there are now more people driving more cars.

With the MacArthur grant, I realized that people have high expectations of me, that they were placing me in this group of achievers. I compared what Id actually achieved in my life with what I would like to achieve and what other people have achieved, and I found that comparison depressing.

In much of the rest of the world, rich people live in gated communities and drink bottled water. That's increasingly the case in Los Angeles where I come from. So that wealthy people in much of the world are insulated from the consequences of their actions.

We study the injustices of history for the same reason that we study genocide, and for the same reason that psychologists study the minds of murderers and rapists... to understand how those evil things came about.