All recognized famous inventors had capable predecessors and successors and made their improvements at a time when society was capable of using their product.

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.

A blueprint for disaster in any society is when the elite are capable of insulating themselves.

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.

We're uncomfortable about considering history as a science. It's classified as a social science, which is considered not quite scientific.

In the latter case it is often government that organizes the conquest, and religion that justifies it.

Our biggest threat is not an asteroid about to crash into us, something we can do nothing about. Instead, all the major threats facing us today are problems entirely of our own making. And since we made the problems, we can also solve the problems.