Friday, July 3, 2015

Of Microbes & Men

Conservative critics of the biosocial sciences general view the latter as reductionist.  They see it as a series of defeats.  The human mind is reduced to neurobiology, virtue and morality to raw self-interest, human beings to mere animals, animals to accidental products of blind evolutionary processes and those processes to molecular collisions.  I have long seen exactly the opposite in these same sciences.  I have argued in these pages that biology in general and evolutionary biology in particular are not and cannot be reductionist sciences.  The consequences of this insight are metaphysically robust. 
Leo Strauss wrote that
It is safer to try to understand the low in the light of the high than the high in the light of the low. In doing the latter one necessarily distorts the high, whereas in doing the former one does not deprive the low of the freedom to reveal itself as fully as what it is.
That is a clear and penetrating a rejection of reductionism.  I am in complete agreement and I think that evolutionary biology in general and the biosocial sciences in particular conform to Strauss’s principle.  The simplest understanding of the distinction between the high and the low goes like this: the high comprehends the low but is neither comprehended by nor exhausted by the low.  To take a simple example: consider the First Methodist Church in Aberdeen, South Dakota.  It is made of bricks, wood, plaster, pipes, wire, and glass, among other things.  While it includes all of these things, none of them is sufficient to explain why it came to be or why it has been sustained over the last century.  To understand that, you have to know something about the human turn toward the Divine, along with a lot of knowledge about human beings form societies, cooperate and pool resources, form networks, etc. 
I was led to these thoughts this week when reading a marvelous essay: “Evolution of cooperation and control of cheating in a social microbe,” by Joan E. Strassmann and David C. Queller (PNAS, vol. 108, suppl. 2).  Strassman and Queller believe that Dictylostelium discoideum, an occasionally social amoeba, is an excellent model for the evolution of cooperation and the transition in evolutionary history from single cells to multicellular organisms. 
D. discoideum amoebae live as singular cells, engulfing their bacterial prey when there is plenty of the latter.  When food runs out, they aggregate.  They form a slug which, after it has found a suitable perch, transforms into a stalk and bulb formation.  In the bulb are amoebae that have become spores, armored to a ride on the belly of some passing insect or other animal.  

All of this extraordinarily functional behavior depends upon mere molecules.  The amoebae secrete a molecule called “prestarvation factor”.  This is part of a quorum sensing mechanism.  It tells each amoeba how dense the population of its fellows is in the immediate neighborhood.  As long as there is enough food, the factor is suppressed.  When the population grows and the food runs out, it triggers the social stage (or the sexual stage, but I’ll leave that one for later).  Understanding how the molecules work in the mechanisms of the cells is work for a molecular biologist.  One cannot understand what the organism is doing without understanding that it is trying to do something.  The whole includes all the stages of the organism, from single cell to hopeful tower. 
The most interesting thing that Strassmann and Queller explain is that D. discoideum is a political animal (my phrase).  Its strategy requires a social contract, with benefits for cooperation and penalties for cheating.  The amoebae are not all genetically identical.  They are divided into diverse clones with distinct traits and distinct reproductive interests.  Any clone that exists is the offspring of previous amoebae that successfully navigated the process of sustenance, transportation and reproduction.  That defines its interest in the process. 
When a stalk and bulb is formed, all the amoebae that form the stalk will die.  Only those that end up in the spores will have a genetic future.  That doesn’t matter when the stalk and bulb are formed by a single clone.  However, the construction project frequently includes more than one clone.  The stalk and bulb are a chimera, an organism with more than one genetic identity.  In that case, there is an opportunity for cheating.  One clone might allow another to form the stalk without contributing to that work.  A clone that can get all of its team into spores would cheat a clone that did stalk work.  
That would mean, however, that the cheated clone would eventually disappear from the gene pool.  If that happens, there is no one left to cheat.  The system does not have to be egalitarian.  Some clones can do better than others, at least temporarily.  The system does have to demand contributions from every party and distribute benefits to every party if it is to be sustained. 
Strassmann and Queller do a fine job of laying out all the devices by which cheating is controlled and cooperation ensured in these social amoebae.  They frequently use the language of political theory: social contracts, “veils of ignorance”, etc.  These terms are partially metaphorical, but only partially.  There is a genuine social contract in force among these tiny citizens.  There are genuine conflicts of interest, concessions, sanctions, and a general interest. 
Instead of reducing the higher animals to the lowest ones, biology is busy elevating the lowest ones.  I know enough about Socrates, Plato, and Aristotle, to know who wins here.  Socrates spent most of his time in Plato’s dialogues arguing with Sophists.  The latter argued that justice was a mere human invention, contrary to nature, employed by the weak to hobble the strong.  Socrates argued to the contrary that justice was something real, intrinsic to the nature of things.  The strongest, he argued, had as much interest in justice as the weaker. 
Contemporary biology is proving Socrates right.  Principles of justice govern when slime mold clones congregate, honey bees operate their colonies, and the Continental Congress does the constitutional thing.  None of this deprives the lower organic and inorganic levels of the freedom to fully reveal themselves as what they are.  One cannot, however, understand any of this if one views the high solely in the light of the low. 

No comments:

Post a Comment