The recurrent laryngeal nerve in humans begins in the brain then travels down into the the thorax, loops around the aorta, and travels back up the neck where it innervates the larynx. This pathway doesn't makes much sense. A better design would be to innervate the larynx directly without looping around the aorta.
This isn't much of a problem in humans but in giraffes the recurrent laryngeal nerve has to travel several extra meters in order to get to its final destination. Those who advocate that evidence of design is evidence of God prefer to ignore examples such as these.
But can it be explained by evolution? Of course it can. This branch of the vagus nerve is present in fish were it is the fourth vagus nerve innervating one of the posterior gills. You can trace its evolution as the modern blood vessels evolved in the mammal lineage. Mark Ridley describes it, with diagrams, in his textbook Evolution.
You can also see what the region looks like during development on the Critical Biomass blog.
The point is that this is another example of something that makes sense in the light of evolution but otherwise seems quite senseless. The other point is that Intelligent Design Creationism fails to provide any explanation of phenomena such as the path of the recurrent laryngeal nerve.
This is a well-known example of something that looks like "bad design" and that's why it is often used to refute the main message of the Intelligent Design Creationists. Jerry Coyne uses several examples like this in his book Why Evolution Is True.
Have you ever wondered how the creationists respond to these examples of evolution? Here's an example from Darwin's God by Cornelius Hunter: Are Evolutionists Delusional (or just in denial)?.
Coyne inverts the message to say that imperfect designs make sense in evolution. Of course, but so what? So do perfect designs, and everything in between. All these make sense in evolution just as my bad day yesterday makes sense in astrology and warp drive makes sense in science fiction movies. When you can make up whatever just-so stories come to mind, then everything "makes sense."Are you having trouble following the logic of this argument? Let me help you out with the short version ....
The bottom line is that it is precisely from theology and metaphysics that evolution derives its power. Evolution is proclaimed to be a fact by Dobzhansky, Coyne and the evolutionists not on the basis of speculative science. As Elliott Sober has pointed out, evolution's truth status comes from the assumed unlikeliness of design, and all the theology entailed therein. It is, as Sober put it, Darwin's Principle.
Evolutionists like to make factual claims. One fact that is incontrovertible is that evolution is driven by theological claims--that is a matter of public record. Evolution is a religious theory. What is interesting is that the evolutionist denies any such thing. He may as well be denying the nose on his own face. This is truly a fascinating mythology.
Whether evolutionists are liars, delusional or in denial is difficult to say. What is obvious is that evolutionary thought is bankrupt. Religion drives science, and it matters.
Intelligent Design Creationism is a religious theory that fails to explain most of what we observe in biology. But that's OK since evolution is also a religious theory. Nyah, nyah!
[Image Credit: Critical Biomass]
Hunter would have a point if fish were metaphysical.
ReplyDeleteAs Sober has pointed out elsewhere, bad design by itself is no evidence for evolution, even when compared only to design. It is, as he says in the article Hunter cites, useless or deleterious traits that are shared across species that provide strong evidence of common descent. It isn't just in comparison to design but in comparison to any other proposed explanation, such as Lamarck's idea that organisms separately evolve up a "chain of being," that evolution wins against. Evolution's truth status does not come from the "assumed" unlikeliness of design but from the fact that, out of all the things we've thought of yet to explain the shape of life, it fits the evidence best.
ReplyDeleteI somewhat see Hunter's point, but it is a bit strained given that we aren't talking about hypothetical anatomy here. No one's making up stories about these body parts, honest to god they really are that way >.<
ReplyDeleteCut 'em open and see for yourself! :)
The trouble is such relations of anatomical features across species are predicted to be found. The trouble for evolution would be if we never found these apparent relations.
If the internal structure of each species was remarkably and fundamentally different from the next, that would support ID.
...which actually here should stand for "Independent Design". For that's what the metaphysical difference really amounts to. If god made each species, he could have made every species irrefutably and fundamentally different from the next.
Yet in evolution the "design" requires dependence on working from past forms. Thus we require some level of similarities.
The irony here is that yes, there are times where evolutionists may resort to a religious argument - for example, when countering creationists/IDists they need to point out the obvious flaws in those theological arguments. So an evolutionist may argue that, based on what we know about God (omnipotent, perfect, etc, etc) then there is obviously a flaw in the design or creation process used by that God (and no, just saying the imperfections are all because of some mythical "fall" really doesn't cut it). So, because evolutionists use these kinds of arguments, he claims they are they ones making a religious argument. It's really all rather absurd. But so far everything Cornelius Hunter (Dr? Really?) has written on UD seems completely ridiculous.
ReplyDeleteSuspiciously, the laryngeal nerve of the giraffe was also mentioned here, posted on the very same day as this Sandwalk entry (take a look at the second image). Co-incidence?
ReplyDeleteSarfati, on the other hand, makes the simple claims that what seems to be bad design is just deterioration from an original perfect design.
ReplyDelete(I'm having great fun with his Refuting Evolution tome at the moment)
One slightly off-topic question for you-all. I seem to recall there was a point in time where creationists really had every single species separately created, and then a point where they came up with "variation within kinds", seemingly in response to embarrassing-to-refute modern-day observations.
Am I misremembering? Otherwise, does anyone know who started the "variation within kinds" trend?
Dr. Moran:
ReplyDeleteIn response to the question of laryngeal nerve design and your declaration “But can it be explained by evolution? Of course it can.—You can trace its evolution as the modern blood vessels evolved in the mammal lineage."
"Mark Ridley describes it, with diagrams, in his textbook Evolution.”
In his book Evolution, there appears the following:
“Evolution by natural selection proceeds in small, local steps---”
“These nerves first evolved in fish-like ancestors.”
“During evolution, the gill arches have been transformed: the sixth gill arch has evolved in mammals into the ductus arteriosus---”
“(b) In mammals, the gill arches have evolved into a very different circulatory system.”
“Ancestrally, the direct route for the nerve was to pass posterior to the aorta; but as the neck lengthened in the giraffe’s evolutionary lineage the nerve was led on a detour of increasing absurdity.”
“—with each step taking place as a modification of what is already present.”
Here is my problem in comprehending the overall plausibility of your declarative statement that you can trace its evolution as explained by Dr. Ridley’s diagrams.
The quotes from Dr. Ridley’s book indicate a significant degree of major morphological change from organism to organism.
Two of the quotes declare that these major morphological changes occurred in small steps as modifications from a previous morphological feature.
You comment implies that these morphological changes can be traced in Ridley’s drawings.
I do not see evidence of the step-by-step small morphological changes in the drawings. I only see drawings of morphological structures as completed evolutionary organs in rather distinctly different body forms (fish and mammals).
What am I missing here? Are there other information sources where I can gain a perspective of the step-by-step changes in the "evolution" of this nerve and how the “first” laryngeal nerve originated?
Anonymous asks:I do not see evidence of the step-by-step small morphological changes in the drawings. I only see drawings of morphological structures as completed evolutionary organs in rather distinctly different body forms (fish and mammals).
ReplyDeleteWhat am I missing here? Are there other information sources where I can gain a perspective of the step-by-step changes in the "evolution" of this nerve and how the “first” laryngeal nerve originated?"
It looks like you are missing developmental biology. Organs gradually form, they do not appear suddenly.
If creationists would say that we are so badly designed because their god is stupid, they'd sound a little more plausible.
ReplyDeletei don't see how god could have made it that way, but maybe Zeus, he didn't study anatomy as much!
ReplyDelete