I’m allergic to ID videos. Could you point to (or quote) a few relevant bits?
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It’s one long equivocation, which is to be expected because it’s nothing but a gee-whiz argument from incredulity. Painful to read but different from the dishonest stuff that is a lot more common from ID.
Definitely the latter. Unless you think that platonistic structuralism is an “idea.”
He doesn’t even articulate that clearly.
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He uses leaves as an example of non-adaptive order. All these different shapes of leaves. There is no adaptive reason for these shapes (pretty sure this is false. Doesn’t climate play a role in leaf shape?) These different shapes of leaves aren’t there for any reason. But they are beautiful so it hints at them being built into nature for us to enjoy. It’s just 21 minutes. It’s not the worst thing they have ever put out
For sure. You can even estimate fossil climates by leaf shape.
Say no more. Seriously.
Even if that was true, that would still not mean leaf-shapes are evidence for “structuralism”. They literally could then just be whatever random shape happens to be able to do the job.
That misses the point. He is saying that there is no reason that all these shapes are perceived as beautiful. That can be a valid point, though I don’t know precisely how Denton makes it.
This is actually an example Larry Moran uses in his responses to Denton:
One of my favorite examples has been the shape of leaves. Is the difference between a cluster of five needles (white pine) and two needles (red pine) an example of selection and adaption or an accident? What about the shape of maple leaves? There are 128 species of maple ( Acer spp.) and most of them have distinctly different leaves that vary in shape, color, and size. It’s rather silly, in this day and age, to attribute all of those differences to adaptation.
Trying to convince others of the truth of non-adaptive evolution has been a frustrating experience. It’s been particularly frustrating when dealing with Intelligent Design Creationists who think that evolution by natural selection is the only game in town. They are the most adaptationist people on the planet even though they don’t actually believe in the scientific version of evolution. We know, of course, that they have ulterior motives for focusing their attack on the strawman version of evolution that they call “Darwinism” … I understand that. I understand why they stick to their myopic, old-fashioned, view of evolution in spite of all the evidence that it’s incomplete and misleading. It’s not just stupidity.
But now we have an entirely new phenomenon. Michael Denton recognizes how silly it is to attribute every feature to adaptation. This is, of course, a view that been around for a long time among evolutionary biologists and they have perfectly naturalistic, non-adaptive, explanations that have been published in thousands of scientific papers. Denton won’t acknowledge that.
The section “The Pentadactyl Limb” (pp. 12-13 of the Denton paper) is what really piqued my interest, so I thought I would go into a bit more detail. I may (i.e. will) get some details wrong, and I suspect that there are others here with more expertise on this subject, so I encourage everyone to point out any errors. If I put everything in one post it would be a giant wall of text, so I will try to break this down into digestible chunks.
Starting from a zoomed out view of Denton’s argument, he seems to argue for a hard border between what he calls the functionalist and structuralist viewpoints. On one hand you have the functionalist position where morphology emerges from genetics, and on the other you have the structuralist view where morphology emerges from physical and natural laws. I don’t see a border between those. The function of genetics is based on its physical and chemical characteristics. I suspect Denton is making the mistake of viewing genetics as an abstraction that is made concrete through other means, like human language or computer code.
However, genetics is concrete. The physical interactions between DNA, RNA, and proteins is vitally important to biological function. When you write a sentence down the chemical and physical properties of the ink and paper don’t matter, but with DNA it does matter. DNA is the ink and paper.
Denton states that the pentadactyl limb is the result if laws of diffusion:
How does the reaction-diffusion mechanism produce morphology and patterns in embryonic development, and is it as divorced from genetics as Denton makes it out to be? That’s what I am going to dig into a bit more, and encourage others to do the same if it interests them.
Added in edit:
For those crazy enough to follow along, I will keep an updated list of papers that I am reading through:
Aren’t transcription factors the things that react and diffuse? So how is that not influenced by genetics? This whole structuralist-functionalist and genetic-epigenetic controversy is silly. Bodies are built by physical processes: differential cell growth and death, cell adhesion, cell differentiation, cel migration, and such. But genes influence those processes, and differences between species are caused by differences in DNA sequences. Structural requirements constrain what states of functional elements can arise from current states.
However, it would seem that the five-digit limit is maintained by selection, given that a sixth finger is not an uncommon mutation and that five-fingered tetrapods descend from seven- or eight-fingered tetrapodomorphs.
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This will be old hat for some, but here is simplified explanation of how transcription factors work for the non-biologists who may be interested.
Transcription factors bind to specific DNA sequences and drives the transcription of the downstream gene. If you mutate the transcription factor you can change the DNA sequence that it binds to. If you change the sequence of the DNA upstream of a gene you can change the transcription factors that bind to it, or do away with transcription factor binding altogether. Therefore, this whole process is contingent on DNA sequence, both of the DNA binding sites and the gene sequence coding for the transcription factors.
Transcription factors are usually at the end of a chain of biomolecule interactions. For example, Fgf8 is an important protein in tetrapod limb and cranial development. There is a protein on the surface of some cells that can bind Fgf8, and when this happens it sets off a cascade of genes being turned on and off, somewhat like a set of dominoes or a Rube Goldberg type of device. This is all driven by proteins and DNA binding sites that are dependent on their sequence for their activity.
Mutations in any link in that chain of events can change the final outcome. Again, this is all contingent on DNA sequence. It is all contingent on genetics. There is no physical or natural law that requires these proteins and DNA binding sites to have those sequences.
This is the type of system that controls limb development. Denton claims that limb development is somehow determined by laws similar to salt crystalization, but it isn’t. Limb development is contingent on gene sequences. Evolutionary history is what explains morphology, not natural laws.
I also plan on discussing the specifics of limb development to help drive these points home.
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So what does diffusion have to do with any of this? It’s a complicated process, so I will try to simplify as much as possible.
As the picture in the post above illustrates, there is a whole web of interacting proteins that activate or inactivate one another. Let’s go back to our friend Fgf8:
You can find expression of Fgf8 at the zone of polarizing activity (ZPA), and you can find the figure legend in this paper. The important takeaway is that Fgf8 diffuses outwards which creates a concentration gradient. It is this concentration gradient which helps to define the number of digits.
Different concentrations of Fgf8 will have different consequences with respect to gene regulation, and all of this is due to the specific sequences of different genes and transcription factor binding sites. If you change the sequence of these genes then you may change how they react to different concentrations of Fgf8.
In the diagram above you will also notice that there is a protein called Gli3r. As it turns out, mutations in that gene can result in extra digits AND changes in face and head structure.
If we are asking what is selecting for 5 digits we may have to ask if selection for features in different parts of the body are driving that conservation. In this case, we have a gene that is important in both limb AND cranial development. Earlier, I mentioned that there is a complex web of interaction between genes, and this brings up a point that Denton may have missed. We need to consider the connections between developmental pathways for different parts of the body. Selection for a feature in one region of the may affect a different part of the body.
To summarize the last few posts, I really think Denton went astray with his argument. Conserved features in animals is contingent on DNA sequence and evolutionary history, not on natural laws. If genes were organized differently early on in animal or eukaryote evolution then we would have different limbs. There is no natural law driving evolution towards the tetrapod pentadactyl limb.
I don’t know if these last few posts have been worth other peoples’ time, but thanks for reading if you did.
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You can also change the strength of binding by changing the sequence of a binding site, which can result in small or gradual changes to morphology.
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