The science writer Matt Ridley made his reputation with books like "The Red Queen: Sex and the Evolution of Human Nature" and "Genome: The Autobiography of a Species in 23 Chapters." His latest book, "The Rational Optimist: How Prosperity Evolves" is much broader, as its title suggests. Its subject is the history of humanity, focusing on why our species has succeeded and how we should think about the future.

Although I strongly disagree with what Mr. Ridley says in these pages about some of the critical issues facing the world today, his wider narrative is based on two ideas that are very important and powerful.

The first is that the key to rising prosperity over the course of human history has been the exchange of goods. This may not seem like a very original point, but Mr. Ridley takes the concept much further than previous writers. He argues that our success as a species, as opposed to earlier hominids, resulted from innate characteristics that allowed us to trade. Not long after Homo sapiens emerged, we were using rare objects, like obsidian blades, far away from the source materials needed to produce them. This suggests that large numbers of commercial links were established even at the hunter-gatherer stage of our development.

Mr. Ridley gives many examples of how exchange allowed groups to thrive, by enabling them, for example, to acquire fish hooks or sewing needles. He also points out that even the most primitive human groups today are open to exchange. I've always thought this openness was surprising, considering the risks involved, but Mr. Ridley convincingly describes its adaptive value.

Exchange has improved the human condition through the movement not only of goods but also of ideas. Unsurprisingly, given his background in genetics, Mr. Ridley compares this intermingling of ideas with the intermingling of genes in reproduction. In both cases, he sees the process as leading, ultimately, to the selection and development of the best offspring.