Evolution and Creationism Open Debate ·
Kenneth Gilmore · tSrdesnpool l9al5749all9t13mo0mf mcci:122120iacch30lgpa ft1h ·
Given both the positive response to my previous post on the suboptimal path the tetrapod recurrent laryngeal nerve takes, and the unsurprising but still fractally ignorant creationist rebuttals to it, a deeper dive into how the human body unarguably shows poor design driven by evolutionary contingency is needed if only to provide badly-needed education and a dose of humility to the creationists.
The go-to example is the vertebrate eye. Put simply, the vertebrate eye design is fundamentally broken, because the light sensing cells point away from the light. Speaking as both a doctor and an engineer, this is objectively stupid design, if consciously carried out by an agent. What highlights this poor design is that in nature we have a whole group of organisms with objectively correct eye architecture in the cephalopods, whose light sensing cells point towards the light. The image below [1] shows the differences in architecture between vertebate and cephalopod.
Evolution has no problem explaining this, as the initial choices taken by the common ancestors of the vertebrates and cephalopods were done because they worked at that time, without any thought into limitations arising from this design in future descendants. The creationist however is forced to contend with the reality that the intelligent designer favoured the mere squid with an architecturally-superior retinal design than the alleged pinnacle of creation, humanity.
The first obvious limitation with the vertebrate eye is that its back to front design creates a blind spot where nerves and blood vessels exit the eye. Cephalopods do not have a blind spot because the nerves and blood vessels are behind the light sensors. Apart from the existence of a blind spot, the vertebrate retina is prone to:
Retina detachment
Vision impairment from diabetic retinopathy
VIsion impairment from retinal haemorrhage
Vision impairment from inflammation in the cells before the light sensing cells.
Neurologist Steve Novella, who raises these issues in an excellent paper on the suboptinal vertebrate retina also comments on how damage to the macula, the small area in the eye which gives us high-resolution vision is ultmately contingent on the inferior inverted retina architecture:
"The macula is that part of the retina that has the densest concentration of rods and cones for detailed vision. Within the macula is a smaller area called the fovea which contains only cones and has the highest density of these receptors. The very existence of the macula, however, is a partial fix for the “backward” arrangement of retinal layers with the nerve and blood vessels between the receptors and the direction of light. This limits the density of rods and cones, and so the partial fix is to have one small area cleared of nerves and blood vessels where rods and cones can be denser. However, if the human retina were designed like that of the squid and other cephalopods, this would not be necessary.
"The dependence of the human eye on the macular for sharp vision creates a vulnerability, for any problem with that small area will have a dramatic effect on visual acuity. The rest of the retina will not be able to adequately compensate for the loss or compromise of the macula because the density of rods and cones is just too diffuse.
"Macular degeneration is the most common cause of blindness. Although the cause is often unknown, its severe effects on vision are a consequence of the need for a macula as a partial fix for the poor retinal design." [2]
Novella continues by showing how diseases such as acute angle glaucoma, cataracts, and the suboptimal design of the extraocular muscles that move the eye bear witness to a design that is anything but optimal, but I will not discuss these further as the example of the suboptimal inverted retina is more than enough to show the vertebrate eye design is inconsistent with intelligent design.
Creationists, exquisitely sensitive to the fact the inverted vertebrate retina is bad design have worked overtime to come up with defences of the eye, most of which ignore the fact that while evolution has been able to hone a fundamentally flawed design to create an excellent sensing organ (the average eagle has excellent vision which is several times better than human vision), many aspects of the design optimisation would be unneccesary if the vertebrate retina had the same front-pointing architecture of the cephalopod.
For example, creationists will point to the Müllerian glial cells which act like fibre optic cables [3] in channelling light to the light sensing cells of the retina, ignoring the fact that a retinal design where the light-sensing cells point the correct way would make such an ingenous evolutionary hack unnecessary. It's much like praising the designers of the corrective lenses fitted to the Hubble Space Telescope while ignoring the fact that had the original optics not been badly designed, the corrective lenses would not have been needed.
Recently, the terminally-dishonest creationist site Evolution News has appealed to a paper [4] commenting on the vertebrate inverted retina in order to argue that the inverted retina design is not fundamentally disordered, an argument which makes the same mistake that creationists do when trying to defend the inverted retinal design as optimal, and that subject to the design defect of light cells pointing away from the light, evolution has honed with astonishing efficienty the bad hand evolutionary history has dealt it. These creationist arguments that try to defend the inverted retinal design from an optical efficienty perspective ignore the real design flaws that the inverted retgina give, namely the increased risk of vision loss due to retinal detachment, retinal haemorrhage, macular degeneration and diabetic retinopathy which simply do not exist with a forward-facing retinal design.
One final desperate move creaionists have made is to argue that from a retinal cooling perspective, the inverted architecture is necessary, but apart from the obvious fact that this ignores the existence of the cephalopod retina which doesn't need the inverted retinal architecture for cooling, the creationist argument does not hold water, as molecular pharmacologist Ian Musgrave points out:
"The vertebrate eye does very well indeed, but it is a kludge. The fovea is a cute trick to squeeze greater acuity out of a flawed design, but octopi and squid do it better. The cooling blood flow to the choroid is needed as the pigments of the choroid generate waste heat, but this is irrelevant to whether the photoreceptors are forward or reverse facing. The arrangement of the vertebrate eye does not improve the blood supply, and it looks like the vertebrate eye has to kludge up a high blood flow to the choroid because the vertebrate inverted retina is poorly designed to get blood to where it is needed." [5]
There is for the creationist one ecological fact which serves to mock their concept of intelligent design, and that is the fact deep sea predators such as the sperm whale and the giant squid while living in exactly the same environment and occupying similar niches have such fundamentally different eye architectures. From an intelligent design perspective, the fact God gave two large predators which not only inhabit the same parts of the ocean deeps but frequently meet each other in combat fundamentally different retinal designs is inexplicable, unless one resorts to hand-waving and special pleading. When one recognise evolutionary contingency, the problem vanishes.
Evolution is a tinkerer which selects what works at that moment without a thought for the future, which means a choice that works at one point may lock descendants into a fundamentally flawed design architecture. Evolution over time is able via iterative tinkering to achieve astonishing efficienty - our use of evolutionary algorithms to design confims this - but the fundamental limitations of the initial design will always hamper these design, as the vertebrate retina predisposition to detachment shows.
As I frequently point out, creationists who disagree need to do more than offer a braying hit and run laugh reaction or regurgitate long-debunked platitudes copied uncritically from creationist sources. That requires reasoned thought and evidence from credible primary and secondary literature. I have yet to see a single creationist here even come close to meeting these criteria, and frankly do not expect them to meet it this time.
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Evolution and Creationism Open Debate ·
Kenneth Gilmore · tSrdesnpool l9al5749all9t13mo0mf mcci:122120iacch30lgpa ft1h ·
Given both the positive response to my previous post on the suboptimal path the tetrapod recurrent laryngeal nerve takes, and the unsurprising but still fractally ignorant creationist rebuttals to it, a deeper dive into how the human body unarguably shows poor design driven by evolutionary contingency is needed if only to provide badly-needed education and a dose of humility to the creationists.
The go-to example is the vertebrate eye. Put simply, the vertebrate eye design is fundamentally broken, because the light sensing cells point away from the light. Speaking as both a doctor and an engineer, this is objectively stupid design, if consciously carried out by an agent. What highlights this poor design is that in nature we have a whole group of organisms with objectively correct eye architecture in the cephalopods, whose light sensing cells point towards the light. The image below [1] shows the differences in architecture between vertebate and cephalopod.
Evolution has no problem explaining this, as the initial choices taken by the common ancestors of the vertebrates and cephalopods were done because they worked at that time, without any thought into limitations arising from this design in future descendants. The creationist however is forced to contend with the reality that the intelligent designer favoured the mere squid with an architecturally-superior retinal design than the alleged pinnacle of creation, humanity.
The first obvious limitation with the vertebrate eye is that its back to front design creates a blind spot where nerves and blood vessels exit the eye. Cephalopods do not have a blind spot because the nerves and blood vessels are behind the light sensors. Apart from the existence of a blind spot, the vertebrate retina is prone to:
Neurologist Steve Novella, who raises these issues in an excellent paper on the suboptinal vertebrate retina also comments on how damage to the macula, the small area in the eye which gives us high-resolution vision is ultmately contingent on the inferior inverted retina architecture:
"The macula is that part of the retina that has the densest concentration of rods and cones for detailed vision. Within the macula is a smaller area called the fovea which contains only cones and has the highest density of these receptors. The very existence of the macula, however, is a partial fix for the “backward” arrangement of retinal layers with the nerve and blood vessels between the receptors and the direction of light. This limits the density of rods and cones, and so the partial fix is to have one small area cleared of nerves and blood vessels where rods and cones can be denser. However, if the human retina were designed like that of the squid and other cephalopods, this would not be necessary.
"The dependence of the human eye on the macular for sharp vision creates a vulnerability, for any problem with that small area will have a dramatic effect on visual acuity. The rest of the retina will not be able to adequately compensate for the loss or compromise of the macula because the density of rods and cones is just too diffuse.
"Macular degeneration is the most common cause of blindness. Although the cause is often unknown, its severe effects on vision are a consequence of the need for a macula as a partial fix for the poor retinal design." [2]
Novella continues by showing how diseases such as acute angle glaucoma, cataracts, and the suboptimal design of the extraocular muscles that move the eye bear witness to a design that is anything but optimal, but I will not discuss these further as the example of the suboptimal inverted retina is more than enough to show the vertebrate eye design is inconsistent with intelligent design.
Creationists, exquisitely sensitive to the fact the inverted vertebrate retina is bad design have worked overtime to come up with defences of the eye, most of which ignore the fact that while evolution has been able to hone a fundamentally flawed design to create an excellent sensing organ (the average eagle has excellent vision which is several times better than human vision), many aspects of the design optimisation would be unneccesary if the vertebrate retina had the same front-pointing architecture of the cephalopod.
For example, creationists will point to the Müllerian glial cells which act like fibre optic cables [3] in channelling light to the light sensing cells of the retina, ignoring the fact that a retinal design where the light-sensing cells point the correct way would make such an ingenous evolutionary hack unnecessary. It's much like praising the designers of the corrective lenses fitted to the Hubble Space Telescope while ignoring the fact that had the original optics not been badly designed, the corrective lenses would not have been needed.
Recently, the terminally-dishonest creationist site Evolution News has appealed to a paper [4] commenting on the vertebrate inverted retina in order to argue that the inverted retina design is not fundamentally disordered, an argument which makes the same mistake that creationists do when trying to defend the inverted retinal design as optimal, and that subject to the design defect of light cells pointing away from the light, evolution has honed with astonishing efficienty the bad hand evolutionary history has dealt it. These creationist arguments that try to defend the inverted retinal design from an optical efficienty perspective ignore the real design flaws that the inverted retgina give, namely the increased risk of vision loss due to retinal detachment, retinal haemorrhage, macular degeneration and diabetic retinopathy which simply do not exist with a forward-facing retinal design.
One final desperate move creaionists have made is to argue that from a retinal cooling perspective, the inverted architecture is necessary, but apart from the obvious fact that this ignores the existence of the cephalopod retina which doesn't need the inverted retinal architecture for cooling, the creationist argument does not hold water, as molecular pharmacologist Ian Musgrave points out:
"The vertebrate eye does very well indeed, but it is a kludge. The fovea is a cute trick to squeeze greater acuity out of a flawed design, but octopi and squid do it better. The cooling blood flow to the choroid is needed as the pigments of the choroid generate waste heat, but this is irrelevant to whether the photoreceptors are forward or reverse facing. The arrangement of the vertebrate eye does not improve the blood supply, and it looks like the vertebrate eye has to kludge up a high blood flow to the choroid because the vertebrate inverted retina is poorly designed to get blood to where it is needed." [5]
There is for the creationist one ecological fact which serves to mock their concept of intelligent design, and that is the fact deep sea predators such as the sperm whale and the giant squid while living in exactly the same environment and occupying similar niches have such fundamentally different eye architectures. From an intelligent design perspective, the fact God gave two large predators which not only inhabit the same parts of the ocean deeps but frequently meet each other in combat fundamentally different retinal designs is inexplicable, unless one resorts to hand-waving and special pleading. When one recognise evolutionary contingency, the problem vanishes.
Evolution is a tinkerer which selects what works at that moment without a thought for the future, which means a choice that works at one point may lock descendants into a fundamentally flawed design architecture. Evolution over time is able via iterative tinkering to achieve astonishing efficienty - our use of evolutionary algorithms to design confims this - but the fundamental limitations of the initial design will always hamper these design, as the vertebrate retina predisposition to detachment shows.
As I frequently point out, creationists who disagree need to do more than offer a braying hit and run laugh reaction or regurgitate long-debunked platitudes copied uncritically from creationist sources. That requires reasoned thought and evidence from credible primary and secondary literature. I have yet to see a single creationist here even come close to meeting these criteria, and frankly do not expect them to meet it this time.
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