Scientists develop new theoretical model on the evolution of cooperation

Evolution by definition is cold and merciless: it selects for success and weeds out failure. It seems only natural to expect that such a process would simply favour genes that help themselves and not others. Yet cooperative behaviour can be observed in many areas, and humans helping each other are a common phenomenon. Thus, one of the major questions in science today is how cooperative behaviour could evolve.

Scientists from the Max Planck Institute of Evolutionary Biology in Plön, Harvard University, and the University of Amsterdam have now developed a new model combining two possible explanations - direct reciprocity and - and found that both repetition and structured population are essential for the of cooperation. The researchers conclude that human societies can best achieve high levels of if their individuals interact repeatedly, and if populations exhibit at least a minor degree of structure.

The scientists addressed the question how cooperative behaviour could evolve using a game called the prisoner's dilemma, which considers two types of players: co-operators who pay a cost to help others; and defectors who avoid paying the cost, while reaping benefits from the co-operators they interact with. In general, everyone would be better off if they had engaged in cooperation, but from the point of view of the individual, defection is more beneficial. Selection will therefore always favour the defectors, and not cooperation. Researchers have used population structure and direct reciprocity to explain why cooperation has nevertheless evolved. In structured populations, co-operators are more likely to interact with other co-operators and defectors with defectors. Direct reciprocity involves the repetition of interaction and is therefore based on experiences gained from prior events involving cooperation. In the past, both approaches have been regarded separately.

Using computer simulations and mathematical models, a group of scientists around Julian Garcia from the Max-Planck Institute of in Plön have developed a new model that is taking both concepts into account. They discovered that direct reciprocity alone is not enough, and that population structure is necessary in order to reach a high level of cooperation. When there is some reciprocity, the average level of cooperation increases because alike types are more likely to interact with each other. Additionally, the researchers observed that cooperation occurs if cooperative and defective individuals are highly clustered and repetition is rare. And surprisingly, too much repetition can even harm cooperation in cases when the population structure makes cooperation between individuals very likely. This is due to the fact that reciprocity can protect defectors from invasion by defectors in a similar manner that it prevents cooperation from being invaded by defectors.

"Without population structure, cooperation based on repetition is unstable", Garcia explains one of the main findings. This is especially true for humans, where repetition occurs regularly and who live in fluid, but not totally unstructured populations. A pinch of population structure helps a lot if repetition is present. "Therefore, the recipe for human cooperation might be: a bit of structure and a lot of repetition", says Julian Garcia. This results in a high average level of cooperation.

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More information: Matthijs van Veelena,Julián Garcíac,David G. Randa and Martin A. Nowaka, Direct reciprocity in structured populations, PNAS,
Published online before print June 4, 2012, doi: 10.1073/pnas.1206694109
Provided by Max Planck Society
Citation: Scientists develop new theoretical model on the evolution of cooperation (2012, June 8) retrieved 21 September 2019 from
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Jun 09, 2012
This article would have been radically improved if they explained what _they_ mean by 'structure'.

Jun 09, 2012
In my opinion (which is actually dense aether model based) the people cooperate from the same reason, like the particles do condense under cooling. The rich or sparse society is individualistic, but when the density of people increases and/or the resources are going down (for example during economical crisis), the sectarian and totalitarian tendencies will gradually prevail. The totalitarian society is the analogy of boson condensate in dense aether model - it formed itself inside of poor Germany and Russia after WWW I and after WWW II in weaker form in Cuba, North Korea and East Europe block. The characteristic of totalitarian and/or sectarian society is the phase interface and high degree of its isolation from the rest of civilization. Inside it forms homogeneous structure entangled with propaganda. Now the USA are facing economical recession, so that the socialistic tendencies are on the rise there too. It's physical mechanism and it cannot be essentially avoided.

Jun 09, 2012
In my opinion (which is actually dense aether model based)...

From physics to evolution. I'm starting to think this dense aether stuff is something you've been huffing.

Jun 09, 2012
Note that there are plenty of known cases of cooperation where no specific social structure is needed, but kinship is the key. Say, bee societies - the social structure follows from the kinship relations, but are not needed to predict the cooperative behavior.

@ IronhorseA: Thanks for the new term, and indeed. "Huffyheads", huh?

@ Terriva:

Your opinion is wrong, so worthless as most opinions go: contenders to evolution ("physical mechanism") and relativity ("aether") were both rejected over hundred years ago. And of course no one sane expects physical mechanisms to control innate social behavior - that is nearly as ludicrous as the rest.

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