Contra Genetic Determinism

 One of the things you are warned against if you study (or dare to teach) logic is the strawman argument.  This informal fallacy occurs when someone more or less deliberately constructs a weakened version of her opponent’s argument (the straw man) in order to easily knock it down.  You say that people have a right to bear arms.  Should we really allow anyone to walk around with a grenade launcher? 

My least favorite strawman argument is expressed in the phrase it’s not all in the genes.  When I searched for that phrase a moment ago, Google reported one hundred and fifty-three million results.  It is apparently a popular straw man. 

It is always deployed as if it were a response to someone who claims that it is “all in the genes.”  That phrase indicates the idea of genetic determinism.  It is conceivable that individual minds and behaviors are largely controlled by genes in the same way that a player piano is controlled by the holes in a rotating scroll.  I say largely because I wish to avoid building my own strawman. 

The reason that “all in the genes” indicates a straw man is that no one believes in genetic determinism.  Genes provide the fundamental elements of the recipe that an organism uses to build itself from its beginning and maintain itself during its life.  That is indeed most of the story of how I came to be and continue to be a human being.  It is not at all the entire story nor even the most dramatic part of the story.

Many of the “not in the genes” refer to epigenetics.  How genes are packaged in the nucleus of a cell can determine which genes are expressed and how they are expressed in the actualized individual.  Epigenetic changes frequently result of environmental influences.  A mouse whose mother is devotedly nurtured and fondled by her mother will not only do the same to her offspring, but those offspring will inherit the same tendency.  This is a very important discovery which should be but has yet to be integrated into social science. 

This implicates one of my chief interests as somewhat reconstructed Aristotelian: the concept of species.  This article by Peter Ward in Nautilus tells the story. 

Work along the Great Barrier Reef in the 1990s had shown that two different and accepted species are present. One, Nautilus pompilius, is the most widespread of all the nautiluses across their vast Pacific and Indian Ocean range. The second, Nautilus stenomphalus, is found only on the Great Barrier Reef. It differs from the more common N. pompilius in having a hole right at the center of its shell. (In N. pompilius, there is a thick calcareous plug.) There are also marked differences in shell coloration and pattern of stripes on the shell. But when the Australian species was first brought up from its 1,000-foot habitat alive, in the late 20th century, scientists were astonished to find that N. stenomphalus has markedly different anatomy as well on its thick “hood,” a large fleshy area that protects the interior guts and other anatomical soft parts when the animal pulls into its shell. In N. pompilius the hood is covered with low bumps of flesh, like warts. Meanwhile the N. stenomphalus hood is covered with a forest of brushy projections that rise above the hood like a thick carpet of twiggy moss, or tiny trees of flesh; the coloration of the hood is also radically different.

So we have not one nautilus but two different… what is the plural of nautilus?  The two were recognized as distinct species, but what does that mean? 

A species can be defined as an interbreeding or potentially interbreeding population of organisms (the most useful but not only useful account, in my opinion) or as branches of the phylogenetic tree.  Either way, you would expect the two to have distinct sets of genetic inheritance.  No. 

We caught 30 nautiluses over nine days, snipped off a one-millimeter-long tip of one of each nautilus’ 90 tentacles, and returned all back to their habitats alive (if cranky). All the samples were later analyzed in the large machines that read DNA sequences, and to our complete surprise we found that the DNA of N. pompilius and the morphologically different N. stenomphalus was identical. No genetic difference, yet radically different morphology.

Let’s repeat that: no genetic difference, yet radically different morphology.  Genes do not even determine the final physical structure of an organism such as this, though to be sure they heavily influence it and explain the common morphological traits.  So much for it’s all in the genes. 

I would add that the difference between the two species is not determined by the environment either.  It is determined by the interaction between the common biologically heritable factors and the environment.  The ontogeny, or development of these creatures is a dialogue, not a recitation. 

What is true of biological structures is much truer of minds and behaviors.  A human being becomes what she is by a series of dialogues between her genome and the environment and between herself and the human community with which she interacts.  In this series of dialogues, she is not the least of the dramatis personae.