Soundbite: Darwinian Markets

For millennia, homo sapiens was just another species of hunter-gatherer primates. Then we developed a fantastically complex system of cooperation and specialization unknown elsewhere in nature. In The Company of Strangers: A Natural History of Economic Life (Princeton), University of Toulouse economist Paul Seabright explains how biological dispositions evolved to create the "great experiment" of civilization. Seabright spoke with Assistant Editor Julian Sanchez in March.

Q: Which traits of our hunter-gatherer brains enable market society?

A: The two key characteristics are the ability to calculate and reflect on what's prudent for you, and the ability to respond with reciprocity to others–to respond warmly and generously to others' warmth and generosity. You can't reduce one to the other. We need surveillance mechanisms and rational calculation to cooperate, but also some instinctive emotional need to respond cooperatively to others who are cooperative.

Q: Why have some countries been successful in promoting trust and market exchange?

A:What's important is the associative habits people have and, crudely put, who they're prepared to trust. In the 19th century, Tocqueville was struck by the fact that the U.S. was characterized by an enormous efflorescence of voluntary organizations. If you look at membership in churches, community groups, and so on in the United States, it's very much higher than in most European countries.

We don't know exactly the causes of that, but we can speculate, for example, that feudalism was rather bad for these things, because feudalism encouraged vertical ties. The United States was founded as a commercial republic where right from the start, people had to forge some way of living with people who were in some sense their equals–maybe not their economic equals, but at least in status their equals.

Q: How fragile or robust is our social order today?

A: Most of the conventions that underpin modern society are robust partly because they're extremely decentralized: Nobody's actually enforcing the fact that we all behave in a certain way. We reinforce it ourselves through billions of everyday decisions.

What the sophisticated modern terrorist organizations are trying to do is find a symbolic point of weakness that can threaten the whole edifice, even though the edifice itself doesn't have any kind of central pillar. That's why they chose the Twin Towers, and why a lot of terrorist organizations are very media savvy.