Throughout history, adultery has had few rivals as a cause of murder and human misery. The reason we tend to resemble our mates is that many of us are looking for someone who reminds us of our parent or sibling of the opposite sex, who in turn resembles us.

The rate of human invention is faster, and the rate of cultural loss is slower, in areas occupied by many competing societies with many individuals and in contact with societies elsewhere.

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

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

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.

I'd rather spend my leisure time doing what some people call my work and I call my fun.

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