Rhino-mounted Bantu shock troops could have overthrown the Roman Empire. It never happened.

I decided that now is the time to start doing the things that really interest me and I find important. It was in the 10 years of the MacArthur grant that I began working on my first book... and I began putting more work into environmental history.

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

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.

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.

Why did human development proceed at such different rates on different continents for the last 13,000 years?