In this short post, I’d like to explain what’s wrong with KeithS’s argument for unguided evolution. The argument, in a nutshell, goes like this:
1. We observe objective nested hierarchies (ONH)
2. Unguided evolution explains ONH
3. A designer explains ONH, but also a trillion alternatives.
4. Both unguided evolution and a designer are capable of causing ONH.
Conclusion: Unguided evolution is a trillion times better at explaining ONH.
The first thing I’d like to point out is that while KeithS, in his post over at TSZ leans heavily on the evidence assembled by Dr. Douglas Theobald in his article, 29+ Evidences of Macroevolution, it is very odd that Dr. Theobald himself does not put forward this argument anywhere in his article. On the contrary, he expressly declares, in his reply to creationist Ashley Camp’s critique:
This is not to say that God could not have created species independently and miraculously, yet gradually. While there currently is absolutely no scientific evidence for such an idea, gradual Divine direction of evolution is indeed consistent and compatible with common descent.
It is possible for a theist to see the theory of common descent, and the hierarchy which it predicts, as a reflection of the Creator’s divine plan—much as Sir Isaac Newton saw his laws of motion, and the ellipses and parabolas which they predict, as evidence of the Creator’s hand in our universe…
In fact, no theological assumptions or arguments are made at all in the essay. The “29 Evidences” is not an argument against creation—it is the scientific argument for common descent, no more, no less…
I personally believe that an omnipotent, omniscient Creator could have created in any manner that he chose. For a theist, the pertinent question is not “what is an omnipotent Creator capable of?” but rather “how exactly did/does the Creator create?”. The first question is purely theological, and as such is left unaddressed in the “29 Evidences”; in contrast, the second question is one that science can answer (given the assumption of a Creator).
The second point I’d like to make – and here I’m basically restating a point that William J. Murray made earlier, in mathematical language – is that KeithS has misapplied Bayes’ Theorem, which states: P(A|B) = P(A).[P(B|A)/P(B)],
where A is a proposition and B is the supporting evidence,
P(A), the prior probability, is the initial degree of belief in A,
P(A|B), the conditional probability, is the degree of belief in A, having taken B into account, and
the quotient P(B|A)/P(B) represents the support B provides for A.
A better way of stating Bayes’ Theorem is to expand the denominator, P(B). We can say that P(B) is equal to [P(B|A).P(A))+(P(B|~A).P(~A)], since if B is true, then either A is also true or A is false (and thus ~A is true). Hence:
P(A|B) = [P(A).P(B|A)]/[P(B|A).P(A))+(P(B|~A).P(~A)]
Where P(~A) is the probability of the initial degree of belief against A, or 1-P(A)
P(B|~A) is the degree of belief in B, given that the proposition A is false.
The problem is that KeithS has conflated two hypotheses: the hypothesis of common descent (which is very well-supported by the evidence that objective nested hierarchies exist in living things), and the hypothesis of unguided design (which he also claims is well-supported by the evidence that objective nested hierarchies exist in living things).
The first hypothesis is indeed well-supported by the evidence, as the only known processes that specifically generate unique, nested, hierarchical patterns are branching evolutionary processes. The probability that any other process would generate such hierarchies is vanishingly low.
But if KeithS wishes to argue against intelligently guided evolution, then the two alternative hypotheses he needs to consider are not:
A: a branching evolutionary process (also known as a Markov process) generated the objective nested hierarchies we find in living things; and
~A: an Intelligent Designer generated these objective nested hierarchies,
but instead:
A: an unguided process generated the objective nested hierarchies we find in living things; and
~A: an intelligently guided process generated these objective nested hierarchies.
The point KeithS makes in his essay is that on hypothesis ~A, the likelihood of B (objective nested hierarchies in living things) is very low. However, it is also true that on hypothesis A, the likelihood of B is very low, as the vast majority of unguided processes don’t generate objective nested hierarchies.
My third point is that KeithS’s argument assumes that the genetic and morphological features on the basis of which living things are classified into objective nested hierarchies were generated by the same process as the (unguided, Markovian) processes which generates the branches in the hierarchies. This is unlikely, even on a standard evolutionary view: features take time to evolve, and therefore would presumably have appeared at some time subsequent to the branch nodes themselves. Thus it could well be the case that while unguided processes explain the existence of objective nested hierarchies in the living world, guided processes are required to explain some or all of the features in these hierarchies.
My fourth point is that KeithS’s exclusion of the origin of life from his argument limits the force of his conclusion. At most, he can argue that objective nested hierarchies are best explained by unguided processes; but that is not the same as saying that living things themselves are best explained by these processes, or that the origin of life is due to an unguided process.
Finally, I’d like to point out that KeithS’s argument against Dr. Douglas Axe is factually mistaken. Nowhere in his paper, “The Case Against a Neo-Darwinian Origin of Protein Folds” does Dr. Axe make the argument KeithS imputes to him.
My time at the Internet cafe is up, so I shall stop here.