History as well as life itself is complicated -- neither life nor history is an enterprise for those who seek simplicity and consistency.

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

In contrast [to trees and fish], oil, metals, and coal are not renewable; they don't reproduce, sprout, or have sex to produce baby oil droplets or coal nuggets.

The history of interactions among disparate peoples is what shaped the modern world through conquest, epidemics and genocide. Those collisions created reverberations that have still not died down after many centuries, and that are actively continuing in some of the world's most troubled areas.

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

Although native Africans domesticated some plants in the Sahel and in Ethiopia and in tropical West Africa, they acquired valuable domestic animals only later, from the north.

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.