Keywords: Complexity theory, science, complex adaptive systems

Title: Emergence

Author: Steven Johnson

Publisher: Penguin

Media: Book

ISBN: 0140287752


What do ant colonies, slime moulds and the teeming streets of your average city have in common? Viewed through the lens of complexity theory, they are all examples of complex adaptive systems, and a hall-mark of such systems is that they display emergent behaviour. Steven Johnson's book does not dwell too much on detailing complexity theory to any great extent, there are other books (such as Mitchell Waldrop's or Philip Lewin's pop-science books Complexity), instead Johnson is more interested in the real examples of emergence all around us.

Emergent phenomena, such as the cleaving of a city into different neighbourhoods or the apparent collective intelligence of an ant colony, are by-products of the interactions of thousands of simple agents. An individual ant is fairly unintelligent and is largely driven by instinct. An ant follows a few simple rules: get food, dump waste, tend young, defend the colony. It has limited means of communications with its fellow ants, and what there is largely based on pheromone signalling. But when thousands of ants interact with each other, what you get is not teeming chaos but a global behaviour that can solve problems, keep the colony fed, protect it from attack and can adapt to a changing environment. This is what emergence is all about, this qualitative difference between the simple rules of the agent and the complex behaviour of the mass.

Slime moulds, a favourite example of Johnson's, exhibit even greater levels of emergent behaviour. Slime moulds, and biofilms in general, are formed by individual bacterial cells who somehow get together and organise themselves to act as a collective mass. To all intents and purposes the individual bacteria group together and start acting as though they are a single organism. For a long time it was assumed that there had to be a leader, some super bacterium that controlled and cajoled the rest of the colony. However, surprisingly perhaps, scientists could discover no such microbial dictator. So, who controls the pseudo-organism made up of thousands of individuals? No one.

Just as the ant colony is not controlled and direct by the queen, so the slime mould is not controlled and directed by any single bacterium or group of bacteria. The group behaviour emerges naturally from the simple interactions between the individuals which make it up. The implications for libertarians are obvious: what we have are natural examples of self-organisation.

There are other examples which are much closer to home, of course, and Johnson ranges quite widely, switching from bacterial colonies to city streets to global economies to the Internet. An economy, for example, is also an emergent system, in that it is made up of many thousands of individual agents: consumers, investors, corporations and workers. What emerges from the interactions between these many millions of agents is not a predictable, controllable market but an endlessly evolving marketplace that is never at stasis.

Complexity theory offers a theoretical framework for modelling the activity of phenomena that conventional reductionist approaches to science cannot hope to tackle. The tools of physics cannot be applied to human societies, people cannot be reduced to simple components in the same way that matter can be broken down into sub-atomic particles. However, using complexity theory we can at last begin to imagine modelling societies of complicated, autonomous, rational and irrational people - and that includes creating models of different types of society, not just Western capitalist societies.

Contents © London Book Review 2006. Published March 29 2006