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The evolution of cooperation

Crew cooperationCooperation provides many evolutionary advantages: groups working together can simply do more and, thus, defeat competitors who work as individuals. In fact, cooperation helps to explain how frail, tiny humans reached the top of the food chain. Cooperation is great. So great, that one wonders why more other animals do not have it. If it provides such a large advantage, it should be more common. Out to solve the mystery of cooperation’s rarity, J. B. André (Institut de Biologie de l’Ecole Normale Supérieure, Paris) found that cooperation requires reciprocity, which in turn requires two abilities, neither of which can persist without the other.

Rather than seeing reciprocity as unidimensional, as many biologists do, André sees reciprocity as bidimensional. More specifically, André argues that reciprocity depends on the ability to (1) cooperate and (2) conditionally respond to the cooperation of others. However, the first ability depends on the second for its evolutionary viability, and likewise the second depends on the first. This creates a “chicken-and-egg” problem, where neither ability can exist for very long without the other.

Take the first ability, the ability to cooperate. An organism gains no evolutionary advantage by cooperating with kin that do not respond to this cooperation. In effect, the cooperating animal simply wastes resources, boosting the survival of everyone but itself. Importantly, the kin must not simply respond to cooperation but do so conditionally. That is, an organism being helped via cooperation must recognize the organism that helped it in such a way that it confers some sort of advantage upon the helper. If the helping organism never receives an evolutionarily useful response, cooperation will not last.

On the other hand, the second ability, the ability to respond conditionally to others, presupposes cooperation. Evolving this trait in an environment where no one cooperates confers no advantage. Hence, André argues that these two abilities must evolve independently yet only provide an evolutionary advantage if they evolve at the same time. Neither one leads to the evolution of the other, but neither can one survive without the other. For André, this explains cooperation’s rarity and accounts for its evolutionary advantage and stability.

To test this theory, André constructed a computer simulation which modeled the ability to cooperate and the ability to respond to cooperation as genes. The model allowed for organisms either to respond to cooperation or to “defect,” that is, offer nothing in return (André points out that cooperation by its nature is all-or-nothing).

As expected, cooperation evolved very rarely due to the fact that it requires two abilities that evolve independently of each other yet need each other to confer any evolutionary advantage. The odds of this actually occurring are quite slim, which explains why biologists rarely find cooperation in the animal kingdom.

As André puts it, “Reciprocal cooperation entails an important component of coordination: it is adaptive to cooperate reciprocally when others also do so; otherwise defection is generally a better strategy. In other words, reciprocity is an adaptation to itself.” Furthermore, André argues that there is no reason to assume that reciprocity is a simple, unidimensional trait: if one built a robot to help others, there would be no inherent need for it also to be able to detect being helped. The two are independent. As such, evolution will rarely select for cooperation because rather than evolving as a gradual accumulation of traits over time, cooperation must appear intact, all at once.

For more, see “Mechanistic constraints and the unlikely evolution of reciprocal cooperation” in the Journal of Evolutionary Biology.

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