Why cooperate?

Blogging on Peer-Reviewed ResearchCooperation in nature is very common, and papers about how unlikely cooperation in nature would be are also common. Especially in Nature. (The Journal.)

The latest paper is nicely summarized in a press release from the University of Bristol:

Cooperative behaviour is common in many species, including humans. Given that cooperative individuals can often be exploited, it is not immediately clear why such behaviour has evolved.

...

Professor John McNamara and colleagues demonstrate that when individuals in a population are choosy about their partners, cooperativeness is rewarded and tends to increase.

Professor McNamara explained: "The problem is that the process of natural selection tends to produce individuals that do the best for themselves. So why has a behaviour evolved that appears to benefit others at a cost to the individual concerned?

"In our model, an individual's level of choosiness determines the level of cooperation demanded of its partner. If the current partner is not cooperative enough the individual stops interacting with this partner and seeks a better partner, even though finding a new partner incurs costs."

So when is it worth leaving the current partner and seeking a more cooperative one? Two components are necessary for this to be beneficial:

* There must be better partners out there.
* There must also be time to exploit the relationship with the new partner, which will be true for long-lived animals like humans.

If these conditions are met, natural selection will lead to a certain degree of choosiness evolving. And once this happens, an individual that is not cooperative will be discarded by its partner and must pay the cost of finding another partner.

Thus when there is choosiness, cooperativeness is rewarded and tends to increase. In this way the level of cooperation and the degree of choosiness increase together over time, and cooperation can evolve from an initially uncooperative population.

I'm not sure if this is a trivial finding or an important finding.

The idea derives in part from the concept of competitive altruism. This is where cooperation or altruistic behavior is beneficial to the recipient of this behavior, and being seen as a viable parter is beneficial to the producer of the behavior. Under those conditions, individuals compete to be the more altruistic.

"After you...." "No, really, after allow me..." "No, really, please you go first..." and so on.

The description of the research from the press release is really about general models of cooperation, and does not indicate anything new. The actual study, in Nature, had more subtle findings that do not lend themselves to a press release.

The study at hand used simulations to test the idea that when individuals have the opportunity to repeatedly inteact (in pairs) that the degree of cooperation depends on the amount of potential variation in cooperative tendancy of the different actors in the population. They found that variation (and lifespand of the participants in the model) both positively affect the liklihood of cooperation.

The reason I think this could be a trivial result is that the opposite of variation is no variation (or inability to measure variation) in which case cooperation may be only weakly selected for. The idea that an actor in a cooperative game can defect or cheat is the foundation of the possibility that the actor can actually play along and cooperate. The absence of variation (or the abiltiy to detect variation) is a more complex than necessary way of saying "there is nothing going on here, in nature or our model." The discovery that the variables being measured actually exist, and that the "more" you have (in this case in the magnitude of variation) in the variables, the stronger the effect, may be important in designing models, but not in understanding the evolution of cooperation.


McNamara, John M., Zoltan Barta, Lutz Fromhage & Alasdair I. Houston. (2008) The coevolution of choosiness and cooperation. Nature 451, 189-192 (10 January 2008) | doi:10.1038/nature06455; Received 15 October 2007; Accepted 6 November 2007

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A few days ago I introduced how higher levels of selection could occur via a "toy" example. Obviously it wasn't realistic, and as RPM pointed out a real population is not open ended in its growth potential. I simply wanted to allude to the seeds of how Simpson's Paradox might occur, where…

I think it might still be "a more complex than necessary way" of explaining this.

Right from the start Prof McNamara was over-complicating: "The problem is that the process of natural selection tends to produce individuals that do the best for themselves." That is not really true. If we look back through history, all we can say is that process of natural selection tends to produce agents whose actions tend to result in the continuation and propagation of the genetic patterns within them.

It is obviously not the specific DNA molecules that are kept across generations, only the pattern, hence a genetic pattern that tends to result in the survival of more copies of itself will tend to survive.

So perhaps I am ignoring some hidden complexity, but the longevity and success of genetic patterns that encourage cooperation therefore seems obvious to me.

I'm glad I started subscribing to the feed on journals linking to bp3.org - it's interesting to see how somebody else reports on the same article that I just covered. :)

To clarify your last paragraphs - are you saying that these results are trivial because they don't show that individuals actually have (or develop) attributes such as the ones modeled, nor that they could have evolved? If so, I'm not entirely sure that I'd agree. Aren't many evolutionary explanations in general just that - explanations of why a certain trait or feature, once evolved by happenstance, is beneficial and may rise to fixation? Certainly the paper didn't explain how such features may have evolved in the first place, but they don't seem like more complex than many other genetic behaviors. Or did I misunderstand your criticism?