For those not familiar with “turtles all the way down,” I offer the following from wikipedia.
The most widely known version today appears in Stephen Hawking’s 1988 book A Brief History of Time, which begins with an anecdote about an encounter between a scientist and an old lady:
A well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy. He described how the Earth orbits around the sun and how the sun, in turn, orbits around the centre of a vast collection of stars called our galaxy.
At the end of the lecture, a little old lady at the back of the room got up and said: “What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise.” The scientist gave a superior smile before replying, “What is the tortoise standing on?” “You’re very clever, young man, very clever,” said the old lady. “But it’s turtles all the way down.”
The association of Russell with this story is most likely due to Russell’s telling of a version of the story in his 1927 essay Why I Am Not a Christian (in discounting the “First Cause” argument intended to be a proof of God’s existence): “If everything must have a cause, then God must have a cause. If there can be anything without a cause, it may just as well be the world as God, so that there cannot be any validity in that argument. It is exactly of the same nature as the Hindus’ view, that the world rested upon an elephant and the elephant rested upon a tortoise; and when they said, “How about the tortoise?” the Indian said, “Suppose we change the subject.” The argument is really no better than that.
Russell apparently did not know or could not conceptually grasp the notion that time itself came into being at the origin of the universe, so the question of the origin of the cause of the universe is completely meaningless. Something must exist on the time line of the physical universe in order for the question of origins to have any meaning at all. But I digress.
So, how is Darwinism “turtles all the way down”? Just search and replace “turtles” with “speculation.”
In a previous UD comment I noted that Darwinian explanations for the evolution of anatomical features (e.g. the eye) depend on easily imagined, but undemonstrated, gross morphological and naturally selectable pathways. But I also noted that the starting point, a light-sensitive spot, would be of no use, without colossally complex mechanisms that could transform photon collisions into neurological signals that could result in meaningful muscle movements.
Commenter Hawks retorted: “The old ‘something cannot possibly have evolved unless it was for the sole purpose of doing what it is doing in modern organisms’, aka ‘something had to evolve the intricacies of whole biochemical pathways (including all its enzymes) all at once in one feel swoop’ argument. It is very convincing.”
This is the now tiresome co-option fantasy which I blogged about here.
So, you see, Darwinian “theory” really is turtles (oops, speculation) all the way down. Speculate about imagined but undemonstrated morphological pathways, and when challenged to explain the engineering that would be required, speculate about imagined but undemonstrated and highly improbable co-option scenarios.
When it comes to Darwinism, this is how “science” works.