I’ve sometimes been stumped by a creationist question about evolution. Not unable to give a satisfactory answer, you understand, but unable to understand why the questioner asked the question in the first place. Why, I have often wondered, do people ask questions like “if we’re evolved from apes, why are there still apes?” Do they imagine, I have wondered, that the theory of evolution says that all animals of a species change at once?
Reading “What Evolution Is” by Ernst Mayr (ISBN 0-297-60741-3) has shed some light on that question. In this very methodical and clear account of evolutionary thought, Chapter 4, How And Why Evolution Takes Place, describes the difference between Darwin’s “population thinking” and the philosophical ideas it supplanted.
According to Mayr it’s all Plato’s fault. Or rather, the Pythagorean school that inspired his thought. For over two millennia the essentialist thinking of the Pythagoreans ruled the thinking of European philosophers. This inspired the monadism of Leibniz, for instance. Species were fixed. The very words species and genus were used by Plato’s greatest student, Aristotle, to describe a natural essence–an unchangeable form that was eternally defined by its characteristics. These ideas died hard, and in many ways they’re still with us.
One alternative to fixed species, that was favored by Jean-Baptiste Lamarck, was Transmutation of species. The transmutationism of Lamarck found favor with English thinkers such as Charles Darwin’s grandfather Erasmus Darwin, the computer pioneer Charles Babbage who appears to have envisaged the rolling out of new species according to a divine computer or jacquard loom program, and the publisher Robert Chambers.
In time, Darwin’s population thinking won out, but for a while it was not obvious that the old pythagorean concepts were going to lie down and die.