We are at once the problem and the only possible solution to the problem.

Wrangham cites several studies indicating that in fact humans don't do well on raw food: they can't maintain their body weight, and half of the women on a raw-food regimen stop menstruating. Devotees of raw food rely heavily on juicers and blenders, because otherwise they would have to spend as much time chewing as the chimps do. It is difficult, if not impossible, to extract sufficient energy from unprocessed plant matter to power a body with such a big, hungry brain.

Okinawa, one of the longest-lived and healthiest populations in the world, practice a principle they call hara hachi bu: Eat until you are 80 percent full.

There are fundamental tensions between the biological reality of the planet and the economic reality. To some extent you can adapt the economy, create a new set of rules and incentives to send it down a better track, but finally people in the first world are going to have to consume a whole lot less.

The sheer novelty and glamor of the Western diet, with its seventeen thousand new food products every year and the marketing power - thirty-two billion dollars a year - used to sell us those products, has overwhelmed the force of tradition and left us where we now find ourselves: relying on science and journalism and government and marketing to help us decide what to eat.

Anyway, in my writing I've always been interested in finding places to stand, and I've found it very useful to have a direct experience of what I'm writing about.

If you're a politician it's very useful to say that we can have economic growth and at the same time green the economy, but writers just have to face up to the fact that there are some fundamental tensions between the economic order and the biological order.