'Chiefs, thieves, and priests': science writer Matt Ridley on the causes of poverty and prosperity.

• Author: Bailey, Ronald
• Position: Interview

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MATT RIDLEY, an Oxford-educated zoologist, turned to journalism in 1983, when he got a job as The Economist's science reporter. He soon became the magazine's Washington correspondent and eventually served as it's American editor. This time in the United States had a profound intellectual effect on Ridley, ultimately leading him to become a self-described classical liberal, a "person who believes in economic freedom and social freedom, too."

Ridley, 50, has written several superb books that combine clear explanations of complex biology with discussions of the science's implications for human society. In The Origins of Virtue: Human Instincts and the Evolution of Cooperation (1997), Ridley showed how natural selection led to human morality, including the development of property rights and our propensity to exchange. At the end he warned that government can subvert our natural tendency to cooperate. "We are not so nasty that we need to be tamed by intrusive government, nor so nice that too much government does not bring out the worst in us," he concluded. Reviewing the book for reason, the UCLA economist Jack Hirshleifer noted that "Ridley leans in the anarchist direction."

Written just before researchers announced the completed sequencing of the human genome, Ridley's Genome: The Autobiography of a Species in 23 Chapters (2000) toured our 23 chromosome pairs to illustrate how genes cause disease, direct the production of proteins, and influence intelligence. While pointing out the differential heritability of many human characteristics, Ridley condemned genetic determinism and eugenics as unscientific. "Many modern accounts of the history of eugenics present it as an example of the dangers of letting science, genetics especially, out of control," he wrote. "It is much more an example of the danger of letting government out of control." Ridley further deflated genetic determinism in Nature via Nurture: Genes, Experience, and What Makes Us Human (2003), which explained how genes change their expression in response to environmental influences.

Ridley is now working on a book about how and why progress happens. During a visit to Blagdon Hail, Ridley's home outside Newcastle upon Tyne, I took advantage of the author's weakened state (he had broken his collarbone falling from a horse) to talk about the new book.

reason: What's the book about?

Matt Ridley: My last three or four books have all argued that there is such a thing as an evolved human nature which is true all over the world and has been true throughout history. But something changes. Clearly, my life is completely different from what it would've been if I was an Ice Age hunter-gatherer. Technology changes. Society changes. Prosperity changes. What I want to do is turn the question on its head and come at it from the point of view of an evolutionary biologist who looks at this species--man--which has a constant nature but has somehow acquired an ever-changing lifestyle. I want to understand what's driving that change. Let's give it the obvious word, even though it's a very unfashionable one: progress. The book is about where progress came from, how it works, and, most important, how long it can continue in the future.

My major themes are specialization, exchange, technology, energy, and then population. Human beings have progressed in material living standards, on the whole, since the Stone Age, but they've also progressed enormously in terms of the number of people on the planet. That's because we got better at turning the energy available into people, and the denser the population has got, the more things we've been able to invent that we wouldn't have been able to invent with a sparse population. For example, if you're going to smelt metals, you need a fairly dense population of customers before it's worth building kilns.

Population density can also lead to reductions in the standard of living. There must be cases in history where people have tried to live at too a high a density for the resources that were available to them. They've either then suffered one of Malthus' positive checks--war, famine, and disease--or, and this is a slightly more original point, they've reduced their division of labor, i.e., they've returned to serf-sufficiency.

If you look at the Bronze Age empires in Mesopotamia or Egypt, or the Roman Empire, or some of the Chinese dynasties, at a certain point the population density gets too high for people...