Doberman Pinscher (credit: Wikimedia Commons) 

In a more scientific example of Bayesianism working in my own thinking, I will also mention our Doberman Pinscher–cross pup. Rex was basically a good dog, but he was a mutt, a Doberman cross we acquired because one of my aunts could not keep him. People often remarked that he looked like a Doberman, but his tail was not bobbed. This got me curious. When I learned that most Dobermans had had their tails bobbed for many generations, I wondered why the tails, after so many generations of bobbing, had not simply become shortened at birth. I asked a Biology teacher at my high school, but his answer only confused me. Actually, I don’t think he understood the crucial features of Darwinian evolution theory himself.

                                                                        

                        

                                                  Jean-Batiste Lamarck (credit: Wikimedia Commons)

Once I got to university, I took several Biology courses. Gradually at first, and then in a breakthrough of understanding, I came to realize that I had been thinking in terms of the model of evolution called Lamarckism. At first I did not want to let go of this cherished opinion of mine. I had always thought of myself as progressive, modern, scientific; I did not believe in creationism. I thought I knew how evolution worked and that I was using an accurate understanding of it in all of my thinking. It was only after I had read more and seen by experience that bobbing dogs’ tails did not cause their pups’ tails to be any shorter that I came to a full understanding of Darwinian evolution.

Evolution for all species proceeds 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, 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 genes it carries in the sex cells that govern how long the pups’ tails will be. Under Lamarckism, by contrast, an animal’s genes are pictured as changing because the animal’s body has been injured or 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 has had to use its arm muscles a lot.

But Darwinian evolution gives us what we now see as a far more useful picture. In nature, individuals within a species that are no longer well camouflaged in the changing flora of their environment, for example, become easy prey for predators and so they never survive long enough to have babies of their own. Or ones that are unable to adapt to a cooling climate die young or reproduce less efficiently, while their thicker-coated, stronger, 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, as a consequence, there will be many more individuals with the shorter tail that has now become a normal 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 suddenly became clear, and it gave a deeper coherence to all of my ideas and observations about living things. For me, Lamarckism became just an interesting footnote in the history of Science, sometimes still useful because it showed me one way in which my thinking, and that of others, could go wrong.