6/10/2019

Probability and evolution

Filed under: — Bravus @ 8:39 am

There are a range of arguments against evolution that rely on the notion that it is inherently so improbable as to be impossible. They date right back to William Paley, who published his ‘watchmaker argument’ in 1802, predating Darwin’s ‘Origin of Species’ by more than 50 years.

Essentially, this is the notion that the appearance of design implies the existence of a Designer. It’s also linked to the analogy of ‘a tornado in a junkyard creating a functional Boeing 747 aircraft’, and to the ‘infinite number of typing monkeys creating the complete works of Shakespeare if given an infinite amount of time’.

I’ve tried to avoid linking out to things elsewhere in this series and to make them self-contained, but this paper from 1971 in American Biology Teacher has a perfect example of the kind of thing I’m talking about, in the section entitled “How Many Genes Could Exist?”

Using the usual approach used in these kinds of arguments, that piece comes up with a probability of 1:10600 for the random evolution of all possible genes. That’s a genuinely outlandish number: to give you a sense, the number of atoms in the known universe is on the order of 1080. If that number were correct, then indeed it would seem wildly improbable that life could evolve.

This short post is just about explaining why it is not.

First, that assumes entirely random processes without a step-wise process of natural selection. It assumes that it is necessary (to mangle a metaphor) to arrive at the Boeing 747 without passing via the Wright Flyer and successive improvements.

Second, it assumes that a specific outcome is the goal, whereas biology has a very large range of possible ways to solve the same problems. There are different kinds of wings and eyes and different types of legs and different models of fish locomotion and… Again, to play with metaphors, it’s not inevitable that the monkeys will arrive at the complete works of Shakespeare: they might end up with Stephen King or Iain M Banks or S T Colleridge instead.

These two objections may not sound like much, but together they essentially mean that the statistical and probability claims against the evolution of life do not hold water. Statistical models are only valid when they accurately model the phenomenon of interest… and these simply don’t.


For ease of navigation I will include links to each of the other posts in this series at the bottom of each post.

Why I think it’s important to understand evolution
Cosmogenesis, abiogenesis and evolution
Evolution and entropy
Facts, Theories and Laws
Radiocarbon dating
Radiometric dating and deep time
Four Forces of the Universe
Species and ‘baramin’, macro- and micro-evolution
Mitochondrial Eve and Y-chromosomal Adam
Transitional fossils
Complexity – irreducible and otherwise