We know from our recent history that English did not come to replace U.S. Indian languages merely because English sounded musical to Indians' ears. Instead, the replacement entailed English-speaking immigrants' killing most Indians by war, murder, and introduced diseases, and the surviving Indians' being pressured into adopting English, the new majority language.

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

Even to this day, no native Australian animal species and only one plant species-the macadamia nut-have proved suitable for domestication. There still are no domestic kangaroos.

Measles and TB evolved from diseases of our cattle, influenza from a disease of pigs, and smallpox possibly from a disease of camels. The Americas had very few native domesticated animal species from which humans could acquire such diseases.

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.

Science is often misrepresented as "the body of knowledge acquired by performing replicated controlled experiments in the laboratory." Actually, science is something broader: the acquisition of reliable knowledge about the world.

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.