Eurasia ended up with the most domesticated animal species in part because it's the world's largest land mass and offered the most wild species to begin with.

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?

When we stop fighting against death, we are able to wake up to our lives.

All governments suffer a recurring problem: Power attracts pathological personalities.

A negative past is only there to motivate you to start creating a future that's far better than it.

When a man looks into a mirror and can no longer see his own reflection... he has lost his way.

We live in a society bloated with data yet starved for wisdom. We're connected 24/7, yet anxiety, fear, depression and loneliness is at an all-time high. We must course-correct.

We know nothing of religion here: we only think of Christ.

Even the most solid of things, and the most real, the best-loved and the well-known, are only hand shadows on the wall. Empty space and points of light.

One thing that previous practice doesn't always make perfect: Marriage.

I can't blame Angela Merkel for saying she wants a strong euro.

I'm a sucker for nice religious leaders. I fall for it every time.