It invites a search for ultimate causes: why were Europeans, rather than Africans or Native Americans, the ones to end up with guns, the nastiest germs, and steel?

In fact, everywhere in the world there has been a flux between big and small societies. Big political units are constantly being formed, later to fragment. The individual pieces try to pull apart, and then they join together again. One sees that in Europe: There have been unifications and then dissolutions and reunifications. So in the long run, it's 10,000 steps toward amalgamation offsetting 9,999 steps toward falling apart again. In businesses and industries, I would guess that's also true.

Forced to choose between limiting population or trying to increase food production, we chose the latter and ended up with starvation, warfare, and tyranny.

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.

Ahead of me lies the familiar litany: weakening of the heart, hardening of the arteries, increasing brittleness of bones, decreases in kidney filtration rates, lower resistance of the immune system, and loss of memory. The list could be extended almost indefinitely. Evolution seems indeed to have arranged things so that all our systems deteriorate, and that we invest in repair only as much as we are worth.

The United States has long thought of itself as the land of infinite plenty, and historically we did have abundant resources. But now we are gradually exhausting our fisheries, our topsoil, our water. On top of that, we're coming to the end of world resources.

Perhaps our greatest distinction as a species is our capacity, unique among animals, to make counter-evolutionary choices.