The adoption of agriculture, supposedly our most decisive step toward a better life, was in many ways a catastrophe from which we have never recovered.

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.

For anyone inclined to caricature environmental history as 'environmental determinism,' the contrasting histories of the Dominican Republic and Haiti provide a useful antidote. Yes, environmental problems do constrain human societies, but the societies' responses also make a difference.

The Anasazi did manage to construct in stone the largest and tallest buildings erected in North America until the Chicago steel girder skyscrapers of the 1880s.

The past was still a Golden Age, of ignorance, while the present is an Iron Age of willful bliss.

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.

With the rise of chiefdoms around 7,500 years ago, people had to learn, for the first time in history, how to encounter strangers regularly without attempting to kill them.