What is the driving force behind organic and cultural evolution? Non-zero-sumness, answers Robert Wright in his book Nonzero: The Logic of Human Destiny. Wright explains that in game theory, a contest with a winner and a loser is a zero-sum game. When both contestants are winners, it becomes a non-zero-sum game. The premise of Wright's book is that non-zero-sum contests in evolution tend to produce more fit individuals and species.

Accepting that premise assigns an arrow to both organic evolution and cultural evolution, and that arrow points in the direction of constantly increasing complexity. Wright doesn't quite say that we were preordained, but he does say that we, or something very like us, were much more likely to have evolved as we did rather than in some less complex way. He even dances around the idea that evolution tends to favor what we call "goodness" in preference to something else.

In the first and largest section of the book, "A Brief History of Mankind," Wright traces human progress from hunter-gatherer tribes, to chiefdoms, to kingdoms, to nation-states, and to the first baby steps we have just now taken toward a world confederation.

Wright posits that all cultures began as hunter-gatherer families or tribes. He further postulates that we all started out with the same genetic endowment. That endowment of intellectual and cultural traits, he says, persists to this day. We all have the drive, first and foremost, to preserve our own hide or genetic endowment. But we also share with all other creatures a drive to preserve the hides and genetic endowments of our near kin. When we protect kin, we ensure that at least the portion of our genetic makeup that is shared will be preserved. The closer the relationship, the more we tend to cooperate. And, says Wright, that cooperation, whether with kin or extended to non-kin, is the essence of the non-zero-sumness that drives cultural evolution.

Hunter-gatherers who were fortunate enough to live in rich environments invented technologies to extract greater benefits from their surroundings for their families. The accretion of these ideas, or memes, enriched the family and tended to favor survival of that family. Use of these memes by other nearby families led to confederations or tribes. Confederation benefited all, because when one group within a larger group had a surplus, it could be shared. The largess would be returned later, when some other family within the tribe was the more fortunate. The increase in group size and complexity improved the larger group's overall success.

When group complexity reached a point that allowed specialization of labor within the group, a chief became necessary to mediate between the members of the group. Each member of the group ceded a portion of his autonomy in exchange for the probability of a more comfortable lifestyle. The chief might have been the best mediator, the best warrior, or the inventor of a new meme. Cooperation, or non-zero-sumness, promoted the survival of this larger cultural organism.

With each improvement in technology - which Wright states is really improvement in the use of information - the social organism becomes more complex and serves its members more reliably. Wright likens this growth through the stages of cultural evolution to the growth of a distributed cultural brain or intelligence. Instead of Adam Smith's invisible hand, we have Robert Wright's continually growing invisible brain leading us onward.

Wright even endeavors to incorporate that notorious zero-sum game, war, into his schema. The winner in war tends to be the stronger and more advanced culture. The unity imposed on such a culture by the war effort can open the way to more growth of the invisible brain. And the author shows how war, or the threat of war, often forces cultures to cooperate or wage peace.

In the second section, "A Brief History of Organic Life," Wright shows how the non-zero-sum paradigm benefited the biological evolution of genes, simple organisms, and then the increasingly more complex organisms that preceded humankind and culture. DNA is itself information that directs the use of energy to replicate more DNA. As DNA, for whatever reason, becomes more complex, the resultant cell may be more efficient or adaptable. By succeeding, the new, more complex cell creates new niches for other cells to exploit. And each advance in complexity opens the way for yet more advances in complexity. Simple cells become complex cells. A complex cell learns to divide and a simple organism is born. Cells in an organism "learn" to specialize and organs are born.

The whole exercise in biological evolution is an exercise in the continually improving ability of life to handle information and energy more efficiently. The end result is a creature with an information-handling organ, the brain, which itself is now beginning to control biological evolution.

In the final section, "From Here to Eternity," Wright offers his synthesis and conclusions. He asks if this process occurred because of some external direction or directive. Is there a God, or was it all just random? Are we, mankind, evolving into a global organism or consciousness? These are questions, not answers.

Wright proposes to show us how evolution has lead to love and then to consciousness, with its knowledge of good and evil. He also shows that at every step there have been losers. Non-zero-sumness has been accompanied by zero-sumness - death or extinction - for many individuals and species. His answer to the question evolution poses appears to be, "I gave up so long ago on an omnipotent and benign deity that I'll take a few wisps of good karma and hope that it signifies something larger." The reader must supply his own answers to these cosmic questions.

Wright, the author of The Moral Animal: Why We Are the Way We Are: The New Science of Evolutionary Psychology, is a longtime science writer and editor. He has written a fascinating book of wide general interest. All of us have at one time or another asked the question, "What does it all mean?" The author doesn't answer the question for us, but he does give us a well-constructed scenario upon which we may base our own speculations.