The mathematics of being nice
Using mathematics to tackle some of biology's biggest questions, Martin Nowak has concluded that an ability to cooperate is the secret of humanity's success. He talks to Michael Marshall about drawing fire from Richard Dawkins, the perils of punishment, and devising the mathematical equivalent of the rules of religion
Why are you so fascinated by our ability to help each other out?
Cooperation is interesting because it essentially means that you help someone else, someone who is a potential competitor. You reduce your own success in order to increase the success of somebody else. Why should you do that? Why should natural selection favour such behaviour? To answer these questions I use evolutionary dynamics, evolutionary game theory and experimental tests of human behaviour.
You say there are five different ways in which we cooperate that give us an edge, in terms of natural selection. Tell me about them.
The first one is called direct reciprocity. This is when individuals have repeated interactions, so if I help you now, you may help me later. There is also indirect reciprocity, which takes place in groups. If I help you, somebody else might see our interaction and conclude that I'm a helpful person, and help me later. That's a reciprocal process relying on reputation.
The third mechanism is when neighbours help each other - cooperators survive in clusters. This is called spatial selection, and it plays an important role, not only for people but for bacteria, animals and plants. Then there is group selection: it may be that our group of cooperators is better off than another group of defectors: here selection acts on two levels, because in our group there is more cooperation.
Group selection has had a tricky reputation, and has been attacked by evolutionary biologists. Do you think it has now been rehabilitated?
The introduction of the concept of group selection, some 40 years ago, was imprecise. But recent mathematical models explain very clearly when group selection can promote the evolution of cooperation. There must be competition between groups and migration rates should be low.
Unless I've lost count, there should be one mechanism left.
The last one is kin selection, which can occur when you help a close relative.
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