Take air quality in the United States today: It's about 30 percent better than it was 25 years ago, even though there are now more people driving more cars.

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

Forced to choose between limiting population or trying to increase food production, we chose the latter and ended up with starvation, warfare, and tyranny.

The adoption of agriculture, supposedly our most decisive step toward a better life, was in many ways a catastrophe from which we have never recovered.

AIDS and malaria and TB are national security issues. A worldwide program to get a start on dealing with these issues would cost about $25 billion... It's, what, a few months in Iraq.

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

Biology is the science. Evolution is the concept that makes biology unique.

Technology has to be invented or adopted.

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

Human societies vary in lots of independent factors affecting their openness to innovation.

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

Facing a language you don't know is like returning to your infancy when your mother tongue used to be a foreign language to you

The finger of suspicion never forgets the way it has once pointed.

Small men, seeking great wealth or power, have too often and too long turned even the highest levels of public service into mere personal opportunity.

I did grow up in a rough neighborhood in Portland, which is an abstract concept for anybody who's rolled through Portland because now it looks like a TV set, literally.

Continuity is how you build a physique.

Well if I was hanging out with The Bellas, I'd be pretty big too.

Surround yourself with people that are going to support you on your journey, and get rid of the ones that don't.

Words are nets through which all truth escapes.

There are no difficulties except for those who worry too much about tomorrow.

It provokes the desire but it takes away the performance. Therefore much drink may be said to be an equivocator with lechery: it makes him and it mars him; it sets him on and it takes him off.