See if this analogy makes sense. A ramp onto which you loose a ball, which can roll down and fall into one of three slots. The configuration is such that the ball must go into one of these slots. It cannot get stuck or jump off the ramp. Suppose, like a pachinko machine, the ramp is covered in plastic to prevent leakage.
Now something will cause that ball to go into one of the three slots, but suppose you’re no expert in physics and can’t figure out the equations of motion. So you don’t know the cause.
But can you agree with me that the ball must go into one of the three slots? As a matter of logic, or information, given the setup, the probability of any slot is 1/3. The probability didn’t cause the ball to end up anywhere; chance isn’t a cause. That the ball could potentially be in one of the slots also wasn’t a cause.
Randomness isn’t a cause, either. Neither “chance.” The ball did not fall “randomly” in any causal sense. It fell because of the physics; our ignorance of the physics means nothing.
The ball had to go into just these three slots. Why? Well, that was the way the setup was designed.
And there it is. The “D” word.
The system from its start to its end could be said to have evolved. Evolution in action! But it could have only evolved in certain set ways. The ball could evolve only into one of three configurations. It could not have evolved into fourth slot, for one doesn’t exist. It could not have evolved into a petunia.
This is a stretch of the word evolution, however, which is why it is only an analogy. But ordinary evolution cannot be different in manner, though of course it differs in mechanism.
When DNA undergoes a mutation it must do so only in certain constrained ways. Like the ball, it must fall into prescribed “slots.” Some thing or things will cause the mutation. Nobody might know these causes, or even the range of possible “slots”. This ignorance is called “randomness”. But randomness isn’t ontological. There is nothing physical there.
These facts are why explanations of evolution are often screwy. Take this example from The Scientist:
Are mutations truly random?
Do genetic mutations really occur at random spots along the genome, as researchers have long supposed? Maybe not, according to a study published online today (January 13) in Proceedings of the Royal Society B, which proposes a mechanism for how new mutations might preferentially form around existing ones.
Truly random has no physical or biological meaning. Here it seems to be a stand in for uniform. Whether mutations are uniform along a genome, or express a preference for other sites, some thing or things still causes each one, and under some constraints. It is the duty of the biology to discover whether these causes are biased towards this or that direction. That is, what the “slots” are and their natures.
Another frequent mistake is made by those anxious to argue evolution is “unlikely”. For example, the paper The Mathematical Impossibility Of Evolution by Henry Morris, Ph.D. Morris’s argument is along the same as we met yesterday, when a fellow calculated the probability you existed was nearly impossible.
All probability—a measure of our information—is conditional on the premises supplied. Change the premises, change the probability. Morris starts with the central error of his opponents, “Mutations are random changes in genetic systems”, as if randomness is a cause, from which he concludes “Since random changes in ordered systems almost always will decrease the amount of order in those systems, nearly all mutations are harmful to the organisms which experience them.”
This is a theoretical conclusion, not one based on observation. (I recall people used to say bumblebees couldn’t fly because aerodynamical theory forbade it.) It seems to also be based on the premise that random is not only a cause but also uniform in action. That would be like saying that while we can only see three slots, theory demands there be four thousand (maybe there are slots besides the three which are too narrow, but which theory insists are options).
Just like “you exist” cannot be that impossible since you, in fact, exist, evolution cannot be impossible because it, as observations prove, exists. The nature of evolution is badly misunderstood on both sides.
We still have not succeeded purging the mysticism of randomness from probability. Frequentist statistical theory is rife with it. But then so are many interpretations of quantum physics.