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

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

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?

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

Stop putting all your dirty laundry out in the open if you are not willing to be judged by them.

Our enemy sees us clearly. They will not start a war. They're worried about one thing: If democracy develops here, if we succeed, we will win

I do believe you're only as sick as your secrets.

Anger itself does more harm than the condition which aroused anger.

The hardest thing of all for a soldier is to retreat.

The hand that gives, gathers.

It's exciting for me to see [Laura Bush] busy and out there enjoying what she's doing. But we always make time to be with each other as well.

The man who has entered into a beautiful union is sure of at least one person to whom he can give the best that he possesses.

My soul, alas, needs these uneasinesses in outward things, to be driven to take refuge in God.

You never know just what you can do until you try.