Evolution by natural selection is not an idle hypothesis. The genetic variation on which selection acts is well understood in principle all the way down to the molecular level.

The global conservation organisations are doing everything they can on modest budgets. They essentially promote setting aside reserves and parks around the world.

Hands-on experience at the critical time, not systematic knowledge, is what counts in the making of a naturalist. Better to be an untutored savage for a while, not to know the names or anatomical detail. Better to spend stretches of time just searching and dreaming.

We don't even know what species are out there, for the most part, particularly when you get down to the microbes and very small invertebrates. They make up the mass of the organisms around us, including the soil we depend on, the soil of cornfields as well as hardwood forests. We haven't taken ecology to the point where we can even make a crude prediction of what's going to happen when we've reduced the living world down to a certain level.

That is the great mystery of human evolution: how to account for calculus and Mozart.

The second half of the 20th century was a golden age of molecular biology, and it was one of the golden ages of the history of science. Molecular biology was so successful and made such a powerful alliance with the medical scientists that the two together just flourished. And they continue to flourish.

If everyone agreed to become vegetarian, leaving little or nothing for livestock, the present 1.4 billion hectares of arable land (3.5 billion acres) would support about 10 billion people.