When I was growing up I used to think that the best thing about coming from Des Moines was that it meant you didn't come from anywhere else in Iowa. By Iowa standards, Des Moines is a mecca of cosmopolitanism, a dynamic hub of wealth and education, where people wear three-piece suits and dark socks, often simultaneously.

A sign in the yard of a church next door said CHRIST IS THE ANSWER. (The question, of course, is: What do you say when you strike your thumb with a hammer?)

But I got a great deal else from the experience. I learned to pitch a tent and sleep beneath the stars. For a brief, proud period I was slender and fit. I gained a profound respect for the wilderness and nature and the benign dark power of woods. I understand now, in a way I never did before, the colossal scale of the world. I found patience and fortitude that I didn't know I had. I discovered an America that millions of people scarcely know exists. I made a friend. I came home.

Book tours are really kind of fun. You get to stay in nice hotels, you are driven everywhere in big silver cars, you are treated as if you are much more important than you are, you can eat steak three times a day at someone else's expense, and you get to talk endlessly about yourself for weeks at a stretch.

I had to drive to Minneapolis once, and went on a back road just to see the country. But there was nothing to see. It's just flat and hot, and full of corn and soybeans and hogs. Every once in a while you come across a farm or some dead little town where the liveliest thing is the flies.

So, if people didn’t settle down to take up farming, why then did they embark on this entirely new way of living? We have no idea – or actually, we have lots of ideas, but we don’t know if any of them are right. According to Felipe Fernández-Armesto, at least thirty-eight theories have been put forward to explain why people took to living in communities: that they were driven to it by climatic change, or by a wish to stay near their dead, or by a powerful desire to brew and drink beer, which could only be indulged by staying in one place.

Perhaps it's my natural pessimism, but it seems that an awfully large part of travel these days is to see things while you still can.