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.

Australia is the most isolated continent.

The single most important problem is our misguided focus on identifying the single most important problem!

I personally am not conscious of my accent.

History followed different courses for different peoples because of differences among peoples' environments, not because of biological differences among peoples themselves

Why were there far more species of domesticated animals in Eurasia than in the Americas? The Americas harbor over a thousand native wild mammal species, so you might initially suppose that the Americas offered plenty of starting material for domestication.

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