In a recent post I asked the following question.
I have a question for non-ID proponents only and it is very simple: Is there even one tenet of modern evolutionary theory that is universally agreed upon by the proponents of modern evolutionary theory?
Then I waited for the answers to come in. I was not disappointed, and I would like to express a hearty “thank you” to the proponents of modern evolutionary theory who participated in the exercise.
I have gone through the comments, and the proponents have nominated the following list as tenets on which all proponents of modern evolutionary theory agree:
1. Common descent
2. Modern organisms descend from very ancient ones.
3. The differences among related lineages have accumulated over many generations of change.
4. The basis of (some of) the differences among individuals is heritable.
5. The relative success of those heritable traits is the basis of evolutionary change.
6. Selection is an important evolution force.
7. Populations connected by gene flow evolve together absent very strong selection pull each population in different directions.
8. Selection is important (I am not sure how this is different from 6).
9. Drift exists.
10. Allopatric speciation is possible.
11. Most speciation processes fit somewhere between the extremes of sympatric speciation and allopatric speciation.
12. All of modern life shares common ancestry, HGT and orphan genes notwithstanding.
13. The following mechanisms of genetic change cause change in lineages, with a bias against reversal:
Mutation (point, indel, duplication and rearrangement)
Gene Conversion
Recombination (several mechanisms including HGT)
14. A parallel process of concentration/dilution of such variant alleles occurs (concentration of one is inevitably dilution of the other), by both sample error (drift) and systematic bias (selection).
15. Only frequency-dependent selection can oppose the progress of such an allele through to the fixation of one variant and elimination of the other. This is rare, so origin-fixation is the norm, long-term. [Later withdrawn]
16. Iterated occurrences of such fixations inevitably change lineages.
17. Isolated gene pools diverge.
18. Species differences are fundamentally due to the tendency of this divergence to proceed beyond the point of interfertility (isolation through prezygotic and postzygotic mechanisms).
19. Higher taxa result from ongoing divergences of historic species.
20. Transition-transversion biases in substitution are due to a biochemical tendency increasing yields of one product over the other.
21. Codon position biases occur and are due to the relative effects of selection and drift on synonymous vs nonsynonymous sites.
OK then. Let’s take a look at this list. They seem to fall into the following five categories.
Category 1: Who doesn’t believe that?
Pretty much everyone on the planet would agree with the following proposition: Animals and plants are different now than they were in the past. Thus, the proposition – while at some trivial level a tenant of modern evolutionary theory – is not that which sets it apart from other theories and accounts for its unique purported explanatory power. Even young earth creationists believe it. Therefore, these propositions cannot be the basis for any claim that the theory (as opposed to some other theory) is true. From the above list the following fall into this category: 1, 2, 3, 7, 9, 10, 12, 14, 16, 17, 18, 19, 20 and 21.
Category 2: Trivial
4. The basis of (some of) the differences among individuals is heritable.
Yes, all evolution proponents agree that genetics exists.
Category 3. It is simply not true that all evolution proponents believe it
It is simply not true, for example, that all evolution proponents believe that natural selection plays more than a non-trivial role in the process. It is also not true that all proponents believe sympatric speciation occurs. 5, 8 and 11 fall into this category. See here and here.
Category 4. I Don’t know what claim is being made
13. The following mechanisms of genetic change cause change in lineages, with a bias against reversal:
Mutation (point, indel, duplication and rearrangement)
Gene Conversion
Recombination (several mechanisms including HGT)
Is the proponent of this claim stating that genetic change and only genetic change causes change in a lineage? If so, it is clearly not the case that all proponents of the theory agree with this; indeed most of them would dispute it. Is the proponent claiming merely that genetics change occurs and somehow that gets fixed in a species? If that is the case, it would fall under category 1.
Catategory 5. Withdrawn: claim 15.
CONCLUSIONS
My suspicions have been confirmed. Proponents of modern evolutionary theory all agree on a set of propositions that even most fervent young earth creationist would also agree on. And nothing more as far as I can tell.
What I was really trying to get at was this: Is there any “core” proposition on which all proponents of modern evolutionary theory agree. By “core” proposition, I do not mean basic facts of biology that pretty much everyone from YECs to Richard Dawkins agrees are true. I mean a proposition upon which the theory stands or falls, and, as I said above, sets it apart from other theories and accounts for its unique purported explanatory power
I have in mind a proposition that would answer David Berlinski’s famous question:
I disagree [with Paul R. Gross’ assertion] that Darwin’s theory is as “solid as any explanation in science.” Disagree? I regard the claim as preposterous. Quantum electrodynamics is accurate to thirteen or so decimal places; so, too, general relativity. A leaf trembling in the wrong way would suffice to shatter either theory. What can Darwinian theory offer in comparison?
Indeed. What does modern evolutionary theory offer in comparison? How can the theory ever hope to be as “solid as any explanation in science” when its proponents cannot seem to agree on a single tenet, the falsification of which would, in Berlinski’s words, shatter the theory?
UPDATE:
In the comments eigenstate pulls Haldane’s famous “rabbit in the Cambrian” out of his hat. I will address that here:
Everyone knows there are no rabbit fossils in the strata that have been labeled “Cambrian.” First, eigen’s sputtering to the contrary notwithstanding, the primary reason a stratum would be called “Cambrian” in the first place is because of the absence of rabbit fossils.
Set that aside for the moment and consider this. The fact that there are no rabbit fossils in the Cambrian strata is a datum. It is a datum for evolutionary theory; it is a datum for young earth creationists; it is a datum for ID proponents. It is a fact on the ground in the same way that people are stuck to the earth with a force of 1G is a fact on the ground. Saying “a rabbit in a Cambrian stratum would destroy Darwinism” is equivalent to saying “if people start floating off into space it would destroy general relativity.” Well, people are not floating off into space and they are not about to. No rabbits have been found in the Cambrian strata and none ever will be. Haldane’s observation amounts to nothing more than “if the facts were different the theory to explain those facts would have to be different too.” It is trivially true and singularly unhelpful.
I take it that Berlinski’s point is very different. The mathematical models of quantum electrodynamics and general relativity make extremely precise predictions (13 decimal points). It follows that those theories have exposed themselves to an enormously high degree of “risk,” because if an observation were to vary from prediction by even an astronomically small degree it would falsify the theory.
Now consider the following exchange:
Barry: And yet unlike respectable scientific theories, there is not universal agreement on a single one of those details that sets [evolutionary] theory apart as an explanatory mechanism.
eigenstate: so what?
Well, here is what. Paul R. Gross’ asserted that Darwin’s theory is as “solid as any explanation in science.” Berlinski retorted that the assertion is preposterous. The point of the OP is that Berlinski is certainly correct. There is not even agreement among evolutionary theorists on what the model should be in the first place; far less has anyone developed a model that would make exquisitely precise predictions equivalent to those made by quantum electrodynamics and general relativity. Thank you eigenstate for confirming Berlinski’s point with your “so what.’