Nonlin's Case Against Common Descent

We aren’t assuming that T. roseae has a mixture of fish and tetrapod features. We OBSERVE that T. roseae has a mixture of fish and tetrapod features. This observation is what makes it transitional, by definition.

What most people misunderstand is that no one is assuming that transitional fossils are caused by evolution. Rather, each and every fossil is a test of the theory, and that test is a nested hierarchy. The mixture of features in fossils should fall into the nested hierarchy predicted by the theory of evolution.

This means that if we were to find a fossil with a mixture of derived bird and mammal features this would be a transitional fossil, AND that fossil would seriously challenge the theory of evolution, perhaps even falsifying it. The theory predicts that there should have never been any species with a mixture of derived bird and mammal features, but it does predict that there should have been species with a mixture of fish and tetrapod features.

As it stands, every fossil we have fits into the predicted nested hierarchy. This is why the fossil record is one of the strongest pieces of evidence for evolution.

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Sorry, where did this start?
Did you address these points?

  1. Exactly what I was saying! A different movie!
  2. More importantly, if this is the first “evidence”, then what were the previous 150 yrs of belief based on?
  3. And what about Coelacanth? You know, the failed prediction star?

How can the mix make it transitional “by definition”?
It’s like saying “a four legged chair is transitional between a tree and a cat… by definition”.

I am pretty sure that if a “fossil with a mixture of derived bird and mammal” ever shows up, someone will come up with an “explanation” to not kill Darwinism. This is exactly what happened to Mendel - they “explained” genetics with the “modern evolutionary synthesis”. Too bad it still doesn’t fit.

Tiktaalik was unlikely to be an ancestor of extant tetrapods. That doesn’t make it any less of a transitional form. Fossils are almost never assigned to an ancestral node in a phylogeny - you’ll basically always see fossil species like Tiktaalik shown as “different movies”, as you put it, for example in this diagram:
miscon_fig7

Notice that this tree clearly doesn’t depict Tiktaalik as an ancestor of amphibians, mammals, lizards, etc. That doesn’t make it any less of a transitional form by the only useful definition of the term.

Who said Tiktaalik was the “first evidence” for evolution?

Do you want to make a point about coelacanths or just keep saying “what about it”? It wasn’t really a “failed prediction” that coelacanths were found to not be extinct. That wasn’t a prediction in the same way that Tiktaalik was a prediction. Coelacanths were thought to be extinct on the basis that they hadn’t been seen in the fossil record for a long time leading up to the present, and hadn’t been found in the wild. After a certain amount of searching present-day habitats and the fossil record, it’s a reasonable conclusion to come to. But this is equivalent to looking at a very large number of swans, observing that they’re all white, and concluding that there are no black swans. This conclusion is a statistical one - reliant on the sample size relative to the total number of swans. So is the extinction of a species in the fossil record. Short of literally searching the entire world, we can technically never be sure that any given species is actually extinct - it’s all about the weight of the stats. In the case of coelacanths, the odds were against them still surviving, so many people provisionally accepted that they were extinct. Bear in mind that huge numbers of fossil species are considered extinct for the same reason, so it’s inevitable that a few of them will buck the odds and turn up alive.

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I’m a bit confused here. Are you saying genetics doesn’t “fit” with evolution?

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Yes, I did address them. Here is the wikipedia definition of transitional fossil:

Here is what Darwin said about transitional fossils:

No one is saying that T. roseae is the direct ancestor of any living species. Therefore, finding earlier transitional tetrapods does nothing to change the transitional nature of T. roseae. The transitional nature of a fossil is determined by the mixture of features in the fossil. Period.

What about the coelacanth? If nothing else, it is proof positive of how many gaps there are in the geologic record and why gaps in the fossil record are not indicative of gaps in the actual evolution of species.

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If a chair was a biologically reproducing organisms with bones such as a humerus, radius, ulna, carpals, femur, tibia, fibia, and tarsals then you might have a point. Those are the homologous features that are used to construct comparisons between species.

A transitional fossil is defined by it’s morphological characteristics, as shown in the wiki definition above.

" A transitional fossil is any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group."

T. roseae has a mixture of features from lobe finned fish and tetrapods. It is transitional by definition because it has those features.

The point is that every fossil we have fits the predicted nested hierarchy which is why every fossil we have is evidence for the theory.

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To be clear, the nested hierarchy is imperfect because of things like convergence, etc.

It gets a bit cumbersome to add the same caveats to every post, but it is prudent to remind readers about the statistical nature of phylogenetics, and really all of science. Almost all measurements and correlations in science have noise, and phylogenetics is no different.

It is very important to add this specific caveat in every time. It is well known to biologists, and not to the public.

Let’s test this. I said: “one must presume evolution to see evolutionary links (the animation movie)”. Now let’s not presuppose “evolution”. Would the tree you show make any sense? Without presupposing “evolution”, what would “transitional” mean?

It is presented as the “definitive” proof.

Not that it was extinct. The failed prediction was that it was a “transitional” organism.

Exactly. Mendel destroyed “gradualism”.

…only if presupposing “evolution”.

“Nested hierarchy” is in perpetual change (attempt to fit “predictions”) because it’s simply “curve fitting” (or “tree fitting” in this case)…
if a tree must be built, a tree will be built as in this example: “The close relationship between animals and fungi was suggested by Thomas Cavalier-Smith in 1987, […] and was supported by later genetic studies. Early phylogenies placed fungi near the plants and other groups that have mitochondria with flat cristae, but this character varies. More recently, it has been said that holozoa (animals) and holomycota (fungi) are much more closely related to each other than either is to plants […].”

That’s like saying that you have to presume the guilt of a suspect in order to get a match with DNA fingerprinting.

Do you understand what a hypothesis is? This is where you take an idea and predict what you should observe if that idea is true. That is what we are doing, testing hypotheses. If evolution is true then we should see a tree-like distribution of shared derived features. That’s the hypothesis. I am not presuming that evolution is true. I am testing the hypothesis of evolution.

Do you object to hypothesis testing?

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As Dr. S writes, this is a common misconception. The fossil record is not evidence for evolution because it is a complete record - far from it - there are numerous gaps and incomplete data.

The reason the fossil record supports evolution is that everywhere we look in the geologic column, fossils appear in sequence with respect to the pattern of Common Descent predicted by evolution. If evolution is not true then there is no reason to expect this pattern, and it should be a simple matter to find fossils which break the pattern (ie: the Precambrian Rabbit), but this never happens. We have no other hypothesis which offers any better explanation for this pattern we see.

We now have genetic data that shows the same pattern of Common Descent as the fossil record. This is an independent line of evidence supporting evolution, and again we have no reason to expect this pattern unless evolution is true.

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Tiktaalik is one of my favorite examples. I use it in reply to people claiming there is no experimental evidence to support evolution.

There was a gap in the fossil record between fish and land-walking tetrapods, and based on evolution hypothesized that such a creature should have existed. Shubin and others examples examined geological records for location of the right age and environment where fossils of such a creature might be found. After several years of searching they discovered the fossils representing the creature we now know as Tiktaalik. This constitutes an experiment based on a prediction of evolution: hypothesis, gathering of data, and confirmation of the prediction. This is very repeatable - we can (and do!) search for other fossils not yet known but predicted by evolution.

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“Gradualism” =/= “evolution”, does it?

The debate between the Mendelians and the Biometricians was settled with the theoretical work that led to the “modern synthesis” or “neo-Darwinism” in the 1930’s. Fisher, Wright, and Haldane showed mathematically that Mendelian genetics was conpatible with evolution.

You’re strawmanning evolution as an incredibly extreme gradualistic idea, forbidding any level of discrete changes. That’s completely false.

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Transitional just implies that a form is intermediate in some way between two other forms. In isolation that information doesn’t necessarily mean anything, but in the context of the other evidence for evolution, and in this case the relatedness of tetrapods and non-tetrapod sarcopterygian fish, Tiktaalik’s form is supportive of that evolutionary transition.

That’s not what you claimed though is it? You said it was the first “proof”, and asked what evidence supported evolution prior to Tiktaalik’s discovery. Tiktaalik may have been portrayed by the popular media as the “first definitive proof” of the “fish-tetrapod” transition, but not the “first definitive proof” of evolution itself, as you implied. Despite what the media headlines might say, Tiktaalik was absolutely not the first “definitive proof” of the “fish-tetrapod” transition, it was just a particularly striking transitional fossil with a nice clean story of discovery that made it appealling to a lay-audience. It doesn’t hurt that it’s discoverer, Neil Shubin, is a gifted science communicator who was able to promote Tiktaalik either. Evidence for the “fish-tetrapod” transition was already definitive long before 2004-2006.

Please elaborate. Exactly what was claimed about coelacanths before they were found to be not be extinct? Are you saying that people were treating coelacanth as a “transitional form” in the sense that extant tetrapods descended from coelacanths, and that the reason coelacanths weren’t found in modern times is because they had gone on to evolve into tetrapods? Or are you saying that coelacanth was treated as a lineage of lobe-finned fish that was closely related to the tetrapod lineage? Only 1 would be accurate.

Much better than most people.

Funny you should mention hypothesis testing and tree-like distribution because this is another extensive discussion on TSZ that you might be interested in. It turns out curve fitting (tree fitting in this case) is not at all hypothesis testing.

Some fossil discoveries predate the “Common Descent” hypothesis which didn’t make any pattern predictions anyway.
Can you prove “genetics independent of morphology”?
The “no other hypothesis” argument has failed too many times in the past.

Tiktaalik “prediction” was discussed - read above. Tiktaalik Blown “Out of the Water” by Earlier Tetrapod Fossil Footprints | Evolution News