The Greatest Show on Earth - Essentialism

I just started reading Richard Dawkins' new book The Greatest Show On Earth.  (I'm actually reading and listening to the recorded books copy.)  I'm sure I will have many comments as I progress in this book, but the first thing that jumped out at me was the question posed in the book: "Why did it take so long for a Darwin to arrive on the scene?"  Also, why to this day are the scientific facts of evolution so challenging to accept?  Dawkins makes reference to the explanation proposed by Earnst Mayr: humans, either by history or by developmental function, are habituated to essentialist thinking while evolution is fundamentally non-essentialist in nature.  I think this is a very intriguing idea.

For any animal, human or otherwise, there is a common ancestor.  This common ancestor is Dawkins calls the hair-pin individual.  You can trace any species back, child to parent, parent to grand-parent, until we reach the hair-pin individual.  From hear we "turn" a sharp bend and travel forward in time from parent to child, following a particular path (with many unventured paths) until we reach the other animal.  All modern animals are cousins of each-other and their sameness or difference as animals is the measure of geologic time needed to trace back to their common ancestor.

So for any point in the chain of ancestors we can identify a species.  Dawkins uses rabbit as his example so I'll do the same.  If we trace the rabbit back in its ancestors we'll reach a point at which we might say, "this is a rabbit but it appears different from my starting rabbit; however, it looks the same as both its parent, grandparent, child and grandchild."  If we keep going back in time we'll eventually reach some creature, a shrew-like creature I think Dawkins mentions, which is clearly not a rabbit.  But at no point along the chain of parent, child and grandparent can we identify a species change.  So at what point in the chain can definitively say, "this animal is a rabbit but its parent is not a rabbit"?  There isn't any point.

Our notion of an object's identity tends towards mathematical essentialism, a kind of Platonic thinking.  But the fact of evolution undermines essentialism.  There isn't any "perfect rabbit" which identifies the form of a rabbit and which to a greater or lesser extent defines the identity of the being as a rabbit by its participation in that form.  Evolution requires a new kind of thinking: population thinking.

Population thinking is statistical and identity is established by properties measured on a normal distribution curve.  I picture this as a bell-curve, the peak of which is any particular animal in our chain of ancestors.  Parents, grandparents, children and grandchildren will appear relatively close on the bell-curve to the individual.  The farther away in time we get from the individual, the farther from our arbitrary norm, the individual are.  When we talk of animal species, all we are doing is placing the peak of our bell-curve on our modern species.