All human societies go through fads in which they temporarily either adopt practices of little use or else abandon practices of considerable use.

The southward advance of native African farmers with Central African crops halted in Natal, beyond which Central African crops couldn't grow - with enormous consequences for the recent history of South Africa.

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 single most important problem is our misguided focus on identifying the single most important problem!

The metaphor is so obvious. Easter Island isolated in the Pacific Ocean — once the island got into trouble, there was no way they could get free. There was no other people from whom they could get help. In the same way that we on Planet Earth, if we ruin our own [world], we won't be able to get help.

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

In short, Europe’s colonization of Africa had nothing to do with differences between European and African peoples themselves, as white racists assume. Rather, it was due to accidents of geography and biogeography—in particular, to the continents’ different areas, axes, and suites of wild plant and animal species. That is, the different historical trajectories of Africa and Europe stem ultimately from differences in real estate.