Friday, June 26, 2015

Plato, Aristotle, Darwin & Indirect Reciprocity

My strategy for pursuing political, moral, and biological questions consists of three basic steps in the following order.  The first is Platonic.  I look for the idea that is expressed in a wide range of phenomena across time and space.  The second is Aristotelian.  I look for the way in which the idea answers different questions in different contexts.  The third is Darwinian.  I look for how the idea might emerge in the evolutionary history of the organisms in which it is expressed. 
Consider the wing.  We recognize wings in a wide variety of animals.  In all cases, it is a biological appendage that allows the creature to gain altitude by beating the air.  In a fundamental sense, the wing of a bat, a bird, a pterodactyl and a dragonfly, are all the same thing.  Plato (or his Socrates) would be pleased.  The wings are very different, however, in their basic design.  One has to lift a heavy reptile; another, a creature as light as a feather.  Aristotle would point this out to his teacher.  The various wings are also examples of convergence.  This is a term in Darwinian explanations that indicates an independent evolution toward a common trait as opposed to homology, which indicates a trait shared because it is inherited from a common ancestor.  Bats and birds don’t have wings because they inherited them from a common ancestor, but because they worked out the same basic mechanics on their own. 
I have found this strategy to be fruitful when applied to my primary interest, morality and politics.  My work on autonomy (which I hope to be published soon) is an example that is illustrated in previous posts.  Here I apply it to reciprocity, one of the basic foundations of cooperation in animals (including human beings).  When some party X pays a cost on behalf of some other party Y because there is a reasonable expectation that the cost will be repaid with profit, that is reciprocity.  That this is a genuinely Platonic idea is indicated by the abstraction of the terms.  It can apply to two teams of dolphins cooperating with one another of different days and to a fellow tipping big at a local restaurant.  Obviously the mechanisms are different.  Less obviously but very likely, they both owe their operation to evolved dispositions. 
Reciprocity is a powerful engine for cooperation, but in its direct form (an exchange between two parties) it is limited to specific exchanges.  When we’re done we’re done.  Indirect reciprocity, by contrast, can knit together much larger communities of cooperators.  This is when an individual is influenced by observing third party cooperation.  In such a case, the cooperator benefits by building a reputation as a good partner.  The observer benefits by recognizing the altruist as a promising partner. 
Tonight I read two accounts of indirect reciprocity.  One was a study of cleaner fish and their clients (Bshary & Grutter, “Image scoring and cooperation in a cleaner fish mutualism”, Nature 22 June 2006).  Cleaner fish feed on ectoparasites in the mouths of much larger fish.  This is a classic example of reciprocity in a morally charged context.  If the cleaner fish eats ectoparasites, it will benefit its larger client.  However, it prefers mucus, if it has a choice.  Eating mucus does not benefit the client.  So the cleaner is tempted to cheat.  In some cases, the client fish is also tempted to cheat by eating the cleaner; however, in most cases the client fish do not prey on other fish.  So how are cleaner fish encouraged to be honest? 
The answer seems to be that client fish pay attention.  They recognize which cleaners are good cooperators and which are not.  They allow the one but not the other to service them.  The cleaners then have an interest in appearing to be good cooperators.  They are more likely to restrain their appetites and eat only the less preferred food (ectoparasites) when they are observed by other potential clients. 
I am pretty sure that there are no moral theorists among Laborides dimidaiatus.  Nor do these tiny denizens of the deep reflect on their behavior.  Their behavior is nonetheless logically moral. 
That this is an expression of a Platonic idea is indicated by the fact that it occurs in very different species.  James R. Anderson et. al., have found it in capuchin monkeys [Cognition 127 (2013) 140-146]. 
Here we show that capuchin monkeys discriminate between humans who reciprocate in a social exchange with others and those who do not. Monkeys more readily accepted food from reciprocators than non-reciprocators or partial reciprocators.
Hitomi Chijiiwa et al found much the same among domestic dogs [Animal Behavior 106 (2015) 123-127]. 
To put it mildly, cleaner fish and their clients, capuchin monkeys, and lapdogs occupy very diverse branches on the tree of life.  It seems likely this is a case of convergence rather than homology.  That makes the case for Plato stronger.  The same basic idea (indirect reciprocity) is expressed independently in a number of distinct cases.  Aristotle would remind us to pay attention to the differences.  Capuchin monkeys and beagles are psychologically social species.  They have, no doubt, a pallet of emotions that from which they paint out their behavior.  As for fish, probably not so much.  Darwinian theory helps us understand how this Platonic idea arises in each case.  
Plato and Aristotle were right, even when they disagreed with each other.  Both of them need Darwin to complete their accounts.  Aristotle understood that teeth make chewing possible is essential to explaining what teeth are.  Darwin explain how chewing explains teeth.  Plato understood that shark’s teeth and his teeth were the same thing.  Darwin explains why Plato was right. 

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