Reply to Bonnie on Evolutionary Explanations

Bonnie’s recent comment involved more than the topic of the last post.  To provide the context for the rest of the comment, my friend Ron posted this:

The problem with all teleological explanations is that many natural phenomena pursue multiple purposes. Although the "purpose" of the human eye is to see... we all look at each other's eyes to form judgments about personality... especially reproductive judgments. The Roman Catholic Church is especially intent on assigning reproductive purpose to monogamous marriage while ignoring friendship as a goal. THUS the question of whether one purpose is more "ultimate" than another purpose is often contingent upon contextual considerations.

This was in response to my recent post explanation and teleology2. I replied as follows:

If by ultimate we have in mind the proximate/ultimate distinction, it seems easy to sort out in case of eyes. Their ultimate function is clearly vision. This is powerfully reinforced by the observation that eyes are temporally and genetically prior to human eyes. Our ancestors had eyes long before the human species emerged.

That we have large whites around our corneas may be an adaptation. It allows us to tell when we are looking into one another's eyes and so facilitates communication. Since chimpanzees don't have such eyes, it is very probably a recent adaptation as runaway selection for intelligence and cooperation shaped our species. At any rate, it seems quite easy to assign these various features to primary and secondary functions.

I won't speak for the Catholics, but Aristotle (who has some purchase with them) also recognized reproduction as the primary function of marriage. This seems to me to be obviously true. It doesn't obviate (in fact it may comprehend) the function of friendship.

Bonnie in turn as this:

On eyes the ultimate (why) final cause of eye as vision could include seeing material objects and forms in the world. If one has an affinity with the poetic understanding of eyes as windows to the soul there are other questions. The ultimate evolutionary purpose of the white of eyes as an adaptive mechanism is purely speculative theory unless tested by scientific method. The science that studies sight at the most refined level is neuroscience.

I reply that the final cause of eyes as vision devices obviously includes seeing material objects and forms in the world.  Cats are looking for prey and prey are looking about for cats.  To test this, I need merely observe the cats and rabbits in my back yard.  The cat moves very slowly, because sudden movement is more visible to rabbits.  The rabbit responds to the cat by freezing, because movement is more visible to cats.  I am sure that the eyes of cats and rabbits are windows to their souls.  Most of what their souls are about is eating and not being eaten. 

What happens in human beings is a lot more poetic, I suspect; but then I am not a rabbit.  When I look at a painting by Joseph Turner, I am not trying to survive or mate.  I am pursuing beauty, which my evolutionary heritage has allowed me to pursue because all the necessary things have been provided.  My agenda is not the same as the agenda of my genes.  Much the same thing is happening when I watch the rabbits play with one another.  They leap at each other and seem to dance.  This may have some adaptive function, but it looks like simple fun.  A cat toying with a mouse is another example.  Good training for hunting, most likely; but a lot more fun for the one than the other. 

Yes, it is speculative that the large whites of human eyes may function to facilitate communication.  It is much easier to tell if a human being is looking at me because I can see the direction of her gaze.  Evolutionary explanations can rarely be tested in the same way that water can be tested for bacteria.  Mostly we have to make do with reverse engineering.  Why the large whites of the eyes?  It might be an accident of eye evolution.  Even if it is, that doesn’t mean that it wasn’t adaptive for another purpose once it was in place.  It might be adaptive for another reason, but the same holds.  All we can say for sure is that it doesn’t look like a complete accident that a species that benefits from interpersonal cooperation has eyes that allow one individual to tell when another is paying attention to her. 

Finally, there is this comment:

If the Greek translation of Aristotle’s ultimate theory carries any weight one might leap to conclusions about the composition of genes. In this era of biotechnology that is a big deal. The courts have wrestled with the question AMP v. Myriad 2013 and have settled upon a kind of genes are like chemistry analogy. It serves Occam’s Razor to simplify its work in resolving disputes between corporate and others interests. According to this analogy the simplest explanation is that genetic information is linear and their coded information is deterministic. Research scientists whose motives exclude the allure of profit and fame as primary incentives, increasingly theorize that a better analogy for the behavior of genes is more quantum physics. Their actions are less predictable than the simplified linear understanding that applies to chemistry. If I am correct, this fits Ron’s remarks about contextual influences.

I have been aware of this for a long time.  Since the discovery of genes, it has been tempting to believe that genes are legible: each codes for one trait and the code can be deciphered.  Once we decipher it, we can edit the code to produce the traits we desire.  I don’t think that anyone in the relevant fields believes that there is a simple, deterministic relation between genes and traits.  A single gene may code for many traits in the body, from the brain to the brawn.  Moreover, many genes depend on environmental inputs for their operation. 

Our genes code for flexibility.  When a cat decides whether to chase a rabbit or a fisherman whether to cast his line, each is making choices.  As I have argued in these posts, evolution works through animals by allowing each to pursue its own agenda.  A bull elk in a rut is not trying to produce the next generation of elk.  He is trying to beat the snot out of other bulls.  When I make dinner for my wife, I am not trying to get my genes into the next generation.  I am trying to make her happy.  That is how the beautiful emerges from the merely necessary.