There's a subtle difference between popular science books written by scientists, and popular science books written by science journalists. Compare Robert Wright's "Nonzero" to Jared Diamond's "Guns, Germs, and Steel". Both are deep-thinking overviews of human history, largely organized along Darwinian lines- but Diamond's book is brain-shaking in a way that Wright's isn't. One hypothesis might be that scientists are just closer to the material, so their thinking is deeper and more nuanced. But I think there's more to it than that- I think science journalists have a kind of inferiority complex, which usually leads them to overplay their hand. That is, they run ahead of the material, liberally sprinkle the text with their own deep-thoughts, and usually end with some sweeping conclusions that are generally unsupported by the evidence they've presented. That's certainly the case here, at least.

Wright's book starts off strong. His theory is that biological evolution and the evolution of human culture are both directional- that is, they tend inexorably to higher levels of complexity over time. The mechanism by which this occurs is cooperation through trade and inter-dependence. As the sphere of cooperation extends from one cell to multiple cells, to organisms, to humans, to villages, to chiefdoms, to states, to empires, to the entire world, the benefits of cooperation power growth to higher levels of complexity. Much of the theoretical underpinning of the argument comes from game theory (Robert Axelrod's excellent "The Evolution of Cooperation" is one of Wright's touchstones)- the phrase "non-zero sum" itself comes from game theory terminology, meaning a game where both players can benefit from cooperation.

So far, so good. Wright deftly handles some basic objections, such as the frequent setbacks that seem to contradict a trend towards complexity. His general retort is that species and cultures that don't effectively harness the power of cooperation will be outcompeted by species and cultures who do, and so, even though the quirks of history (meteors, despotic rulers) may set back a particular species or culture, when viewed as a whole, culture or biology continues its inexorable climb towards complexity. There are, of course, many eminent scientists who disagree with this argument. Wright reserves most of his ire for Stephen Jay Gould, who spent most of his career arguing that species only evolve to "fit" with their environment, and some environments demand complexity, while others don't. Wright offers an effective response here, which is that if you include competition within a species or culture in the calculation, the environment always includes a force which pushes towards greater complexity.

So where does the book go wrong? Mostly at the end, where Wright extends his argument to prognosticating on the future of the human species, and some tangential topics such as the nature of consciousness. Here, I felt like he was making a classic error of extrapolating from too little evidence. Humans have been around for such a short span of time, biologically speaking, and given that we know of only one species that has ever achieved our level of intelligence, it seems a bit of a leap to conclude that the evolution of intelligence is a basic feature of all life in the universe. Likewise, that humans could be considered a single world-spanning organism. And by the time he gets to exploring the idea that the evolution of humans is part of some eternal plan for the universe to "know itself", I felt like we had moved well beyond the realm of science into theology. Maybe Wright wouldn't disagree- his next book is "The Evolution of God", applying evolutionary theory to study of God.

But what about the really important question- what's going to happen to humanity in the future? Jared Diamond argues convincingly in "Collapse" that we're screwed- we'll eventually outstrip our natural resources, like the people on Easter Island, and end in a pretty grim way. Here Wright offers a starkly different opinion, largely based on the same evidence. He feels like we're about to enter a period of serious shake-up, but eventually, through the effect of new information and energy technologies, humans will enter a new golden age, where we peacefully co-exist, respect the Earth, and evolve even higher levels of consciousness. Who you agree with will probably depend on your natural disposition- as a pessimist, I side with Diamond. But as a human, I'm rooting for Wright.