"Trade is to culture as sex is to biology."

This sparkling wit flows from the keyboard of Matt Ridley, a libertarian zoologist who once was on the staff of the Economist. He calls himself "the rational optimist" (the title of his new book), and offers a neat summary of his evolutionary thinking in the Wall Street Journal ("Humans: Why They Triumphed"). In his view, the way sex is essential to biological evolution, trade is at the heart of cultural and technological progress. It was the invention of trade that unleashed a process of increasing specialization and exchange of ideas. The Neanderthals, on the other hand, never adopted trading practices and ended up in the dustbin of history, despite their larger brains. From the very beginning of urban-based civilization, though, the spread of trade was marked by an enormous injustice: "Tax and even slavery began to rear their ugly heads. Thus was set the pattern that would endure for the next 6,000 years — merchants make wealth; chiefs nationalize it." This should probably apply to bankers, too - as Ridley was able to observe first-hand in his capacity as "non-executive chairman" of Northern Rock. He was pocketing GBP 300,000 a year there - until he was forced to resign when the bank cried uncle in September 2007. Luckily, there is light at the end of the tunnel: "Given that progress is inexorable, cumulative and collective if human beings exchange and specialize, then globalization and the Internet are bound to ensure furious economic progress in the coming century — despite the usual setbacks from recessions, wars, spendthrift governments and natural disasters."