Part 3
Chapter 2 – Dogs, Cows and Cabbages
Why did the fact of evolution take so long to discover? Darwin’s theory is so elegant you would think it would have been fathomed out sooner. Perhaps it was the difficulty of grasping the immense periods of time that evolution required or the powerful illusion of design that we see in complex organs like the eye. Dawkins refers back to biologist Ernst Mayr for an interesting and important answer to this dilemma.
For Mayr, the culprit was the "dead hand of Plato".
To Plato everything we experience is nothing more than shadows on the cave wall - imperfect copies an unseen, ideal reality. If you did maths at school or college you may have been amazed (and stumped) by the power of Greek geometers to work out some amazing truths using mental gymnastics. In Plato's world of "essentialism" all the shapes you could ever draw were mere representations of “essential” shapes; the essential triangle really did have angles adding up to precisely 180 degrees, parallel lines of the “essential” rhombus really did extend for infinity without merging.
According to Mayr biology has suffered from its own version of essentialism in which tapirs and rabbits are treated as though they were triangles or dodecahedrons. It is as if there was a perfect essential Platonic rabbit hanging somewhere in conceptual space along with all the perfect forms of geometry. Variation among real rabbits is seen as a departure from the correct form of the essential rabbit to which all bunnies are tethered by invisible elastic.
I find this a very helpful insight. It exposes a way of thinking that is as deeply ingrained as it is flawed and opposed to the evolutionary view of life. Descendants are in fact free to vary endlessly from ancestor forms and every variation in the real world is a potential ancestor to future variants. There is no permanent “rabbitness” no essence of rabbit or tapir or hippo hanging in the sky.
Dawkins proposes a powerful thought experiment to illustrate his point. Imagine going on a walk through evolutionary time to track the path from rabbit to leopard - Let's be clear, rabbits did not descend from leopards or vice-versa. Just like any other two species they descended from a common ancestor.
Like an inspecting general you walk along a line of rabbits, daughter to mother to grandmother back and back through thousands of generations. Change would be so gradual as to be imperceptible like the movement of the hour hand of a watch but eventually we would reach ancestors that are less rabbit like and perhaps more shrew like. Then at some point we reach a hairpin and begin to move forward in time along a separate branch of the tree of life choosing left and right forks in the road until we arrive at a modern leopard.
We could have chosen other directions at every junction and taken a path to any other modern species. At no point in our journey would we notice any changes from one generation to the next. We could choose any two species and do the same thing. This is no mere thought experiment it is exactly what evolution tells us has happened. It is also as far removed from essentialism as it would is possible to conceive.
Hopefully it is also now clear why questions like "if we evolved from chimps why are there still chimps" is so frustrating.
Dawkins observes that psychologists studying the development of language tell us that children are natural essentialists. Maybe they have to be as their developing minds divide their world into discreet categories.
Before summarising the remainder of chapter 2 I would like to illustrate the natural tendency of children towards an essentialist view of the world.
I witnessed an extreme illustration of essentialism when we took our daughter on a visit to Edinburgh zoo when she a little more than a year old. She had evidently fathomed out two models that helped her make sense of the whole animal kingdom "duck" and "cow".
As we wheeled her around the zoo she pointed excitedly at every creature and announced them to be either a duck or a cow. Flamingos, eagles emus etc were all "ducks" every quadruped was proudly declared to be a "cow". Nothing apparently failed to fit into her wonderfully simple world and she looked perpetually pleased with herself for having fathomed out the entire world of zoology at such a tender age.
After lunch we made it to the enclosures near the top of Corstorphine hill. The Penguins came out for their afternoon walk and as they waddled by she mentally ticked of each individual as "duck", "duck", "duck"..... As they went back to their pond, not without stealing a few sandwiches from unsuspecting visitors bags, we turned around to see the giraffes emerging from their house. She stared open mouthed as she looked up and up and up at these four-legged giants that just would not fit into her simple "two creature" model of the world. The word "cow" seemed to stick in her throat; it was a moment of epiphany. A light went on in her head and all our travelling and patience suddenly bore fruit. Her world had changed.
Creationists have just a slightly bigger "duck - cow" view of the world.
In Darwin’s day the word “essentialism” had not been invented but the phrase “the immutability of species” was the received wisdom of the day. It was domestication that proved to be his strongest case against immutability and this occupies the remainder of chapter 2.
