Chapter 7.                    (conclusion) 

Evolution for all species proceeds, mostly, by the combined processes of genetic variation and natural selection. It doesn’t matter how often the anatomies of already existing members of a species are altered if their gene pool doesn’t change. If the species’ gene pool doesn’t change, then the next generation will, at birth, basically look pretty much like their parents did at birth. Chopping off a dog’s tail doesn’t change the tail genes it carries in its sperm or egg cells.

Under Lamarckism, by contrast, an animal’s genes are pictured as changing because the animal’s body has been stressed in some way. Lamarckism says a chimp, for instance, will pass genes for larger arm muscles on to its young if the parent chimp is forced to use its arm muscles a lot.

But Darwinian evolution gives us what we now see as a far more useful picture. For example, in nature, if several plant species in an area are changing their appearance, individual within an animal species there that are no longer well camouflaged in the changing flora become easy prey for predators, and so they never survive long enough to have babies of their own. Or, in another example, ones that are unable to adapt to a cooling climate die young or reproduce less efficiently, while their thicker-coated, or smarter, or better camouflaged cousins flourish.

Then, over generations, the gene pool of the local community of that species does change. It contains more genes for short, climbing legs or long, running legs or short tails or long tails or whatever the local environment is now paying a premium for. Gradually, the anatomy of the average species member changes. If short-tailed members have been surviving better for the last sixty generations and long-tailed members have been dying young, before they could reproduce, the gene pool changes. Eventually, there will be many more individuals with short tails, a now-normal, genetically transmitted trait of the species.

Pondering Rex’s case helped me to absorb Darwinism. My understanding grew and then, one day, through a mental leap, I suddenly “got” the newer, better model. A model I hadn’t understood became clear, and it gave deeper coherence to all my ideas about living things. Lamarckism became just an interesting footnote in the history of Science for me, occasionally still useful because it showed me one way in which my thinking, and that of others, could go wrong.

(To be complete here, I will add that there is now some evidence that, at least in small degrees, stressing an individual can cause its genetic code to alter, though almost always only for a generation or two. This process is called “epigenetic”. But epigenetic changes and their effects on the evolution of that individual organism’s species can be neglected for our purposes here. The evidence shows by far, most of the time, Darwinian processes of variation and selection govern evolution. Bayesianism can, furthermore, accommodate epigenetic models of species change. They are just more nuances to be added to a detailed, nuanced, ever-evolving model of evolution that enables and guides research in the whole, massive field of study called “Biology”. Bayesians are comfortable with that.)

The question that now arises is this: how would the Bayesian way of choosing between the Lamarckian and Darwinian models of evolution or of reshaping one’s views on the mentally challenged compare with the Empiricist way or the Rationalist way of dealing with these same problems?

The chief danger of Empiricism that Bayesians try to avoid is the insidious slip into dogmatism. In the history of Science, many Empiricist-minded scientists have worked out and checked a theory so thoroughly that they have slipped into thinking they have found an unshakeable truth. For example, physicists in the late 1800s were in general agreement that there was little left to do in Physics. Physics, for these people, was complete. Newton and Maxwell, between them, had articulated all the truths of the physical world, from atomic to cosmic. Then, Einstein’s Theory of Relativity overthrew Newtonian Physics.

 

 

                              

                               James Clerk Maxwell (credit: Wikimedia Commons)

 

Today, Physics is in a constant state of upheaval. A few physicists still show a longing for certainty, but most modern physicists are tentative and cautious. They’ve been let down so many times in the last hundred years by theories that once had seemed so promising, but that later were shown by experiment to be flawed, that they have become permanently wary of all “truth” claims. 

It is regrettable that a similar caution has not got into more of the physicists’ fellow scientists and, more frequently, public intellectuals who promulgate and defend science to the general public. They often speak as if Darwinism explains all aspects of the living world we know about or could want to know about. But it is still only a theory; it should be viewed as tentative and likely, but not irrevocable or final. It is part of a bigger, more nuanced model of evolution that is evolving as new data are encountered. (See Dawkins and Wong. ²)

The larger point for our purposes here, however, is that while some who believe Empiricist methods can lead us to truth may present the Theory of Evolution to us as final, Bayesians never endorse any one model as the last word on anything, and they never throw out any of the old models or theories entirely. Even those that are clearly proven wrong have things to teach us, and of the ones that are currently working well, we have to say, simply, that …they are currently working well.

In contrast to Empiricism, Rationalism has other problems, especially with the whole Theory of Evolution and what was going on with my dog, Rex.

For Plato, the whole idea of a canine genetic code that contained the instructions for the making of an ideal dog would have sounded appealing. Obviously, the code must have come from the dimension of the forms, the pure Good. 

But Plato would have rejected the idea that back a few geological ages ago no dogs existed, while some other animals did exist that looked like dogs, but were not imperfect copies of an ideal dog “form.” We know now these creatures can be more fruitfully thought of as excellent examples of canis lupus variabilis, another species entirely. All dogs, for Plato, should be seen as poor copies of the ideal dog that exists in the pure dimension of the Good. But the fossil records in the rocks don’t so much cast doubt on Plato’s idealism as belie it altogether. With regard to gradual, incremental change in all species, Plato’s commitment to “forms” would have led him to totally reject Darwin’s Theory of Evolution.

In the meantime, Descartes’s version of Rationalism would have had serious difficulties with the mentally challenged. Do they have minds/souls or not? If they don’t grasp Math and Geometry and they can’t discuss “clear and distinct” ideas, are they human or are they mere animals? The abilities of the mentally challenged range from slightly below normal to severely mentally handicapped. At what point on this continuum do we cross the threshold between human and animal? Between the realm of the soul and that of mere matter, in other words?

Descartes’s ideas about what properties make a human being human are disturbing. But his ideas about how we can treat non-human creatures are revolting.

To Descartes, animals didn’t have souls; therefore, humans could do whatever they wished to them and not violate any of his moral beliefs. In his own scientific work, he dissected dogs alive. Their screams weren’t evidence of real pain, he claimed. They had no souls and thus could not feel pain. The noise was like the ringing of an alarm clock – a mechanical sound, nothing more. Generations of scientists after him performed similar acts: vivisection in the name of Science. ³

Would Descartes have stuck to his definition of what makes a being morally considerable if he had known then what we know now about the physiology of pain? Would Plato have kept preaching his form of Rationalism if he had been given access to the fossil records we have? These are imponderable questions. It’s hard to imagine either of them would have been that stubborn. But the point is that they didn’t know then what we know now. 

In any case, after considering some likely Rationalist responses to the test situations described in this chapter, it is certainly reasonable for us to say again that Rationalism’s way of portraying what human minds do when they think and know is simply mistaken.

And now, we can put aside for good our regrets about both Rationalism and Empiricism and the inadequacies of their ways of looking at the world. We can go on to a more detailed and comprehensive discussion of Bayesianism.

 

 

 

Notes

 

1. Bayes’ Formula, Cornell University website, Department of Mathematics. Accessed April 6, 2015. http://www.math.cornell.edu/~mec/2008-2009/ TianyiZheng/Bayes.html.  

 

2. Richard Dawkins and Yan Wong; Epilogue to the Mouse’s Tale – On Epigenetics; Richard Dawkins.net; June 8, 2016.

 

3. Richard Dawkins, “Richard Dawkins on Vivisection: ‘But Can They Suffer?’” BoingBoing blog, June 30, 2011.

http://boingboing.net/2011/06/30/richard-dawkins-on-v.html.