Human Eyes Are Wired Backwards(theconversation.com)
theconversation.com
Human Eyes Are Wired Backwards
https://theconversation.com/look-your-eyes-are-wired-backwards-heres-why-38319
11 comments
The picture of the guinea pig says a lot about the intellectual heft of the article...fluffy and not addressing the scientific reality. I'm not a member of PETA, but thinking about the messy reality of experiments on guinea pig eyes is not something I take as being without karmic costs. Grass, sunshine and a bowl of kibble are not what laboratory experiments on animals conjure to my mind.
Exactly, it feels very strange that anyone would find it "rather curious" that the eye has evolved toward a local optimum. And moving the wiring out of the light's path would allow for even more of this concentration mechanism in front of the retina.
You make a good point regarding the author's understanding of color blindness, however gray-scale vision absolutely does exist in humans, albeit in a much smaller proportion of the population than common red-green colorblindness:
https://en.wikipedia.org/wiki/Achromatopsia
https://en.wikipedia.org/wiki/Achromatopsia
>Evolution hill-climbs, so the backwardness (and ensuing disadvantages like the blind spot) can never be fixed.
Well, there's some randomness in there too. I'm sure genetic local maxima get busted sometimes.
Well, there's some randomness in there too. I'm sure genetic local maxima get busted sometimes.
The problem with randomness is that it is overwhelmingly likely to produce worse performance, not better. So much so, that it is practically impossible to improve through random effects.
Random mutations don't have to produce better performance to end up with better results. They just need:
1. To move you to a "bigger hill". Imagine going from no eyes to skin spots that are slightly more delicate than regular skin, but are precursors of light-sensing skin cells^1. Over the course of generations, eyes can evolve.
2. To not be too deleterious. One spot of more sensitive skin won't cause the mutation to be immediately evolved away from; it's just not that bad for the individual.
When you say it's "practically impossible to improve through random effects", what is "practically impossible"? How have you weighed that against the number of individuals in a population, the number of random mutations each offspring has, and the length of time we're talking about? The question isn't "what are the chances a blind fish today has a baby with eyes tomorrow?" This question both understates the number of trials evolution has to generate something, and pins the target of evolution. Instead, we should ask "over millions of years, what are the chances that a given population evolves something useful?"
[1] I'm not claiming this is exactly how eyes evolved.
1. To move you to a "bigger hill". Imagine going from no eyes to skin spots that are slightly more delicate than regular skin, but are precursors of light-sensing skin cells^1. Over the course of generations, eyes can evolve.
2. To not be too deleterious. One spot of more sensitive skin won't cause the mutation to be immediately evolved away from; it's just not that bad for the individual.
When you say it's "practically impossible to improve through random effects", what is "practically impossible"? How have you weighed that against the number of individuals in a population, the number of random mutations each offspring has, and the length of time we're talking about? The question isn't "what are the chances a blind fish today has a baby with eyes tomorrow?" This question both understates the number of trials evolution has to generate something, and pins the target of evolution. Instead, we should ask "over millions of years, what are the chances that a given population evolves something useful?"
[1] I'm not claiming this is exactly how eyes evolved.
There are two different concepts at play here. The first is the notion of optimization by randomness and the second is evolution by natural selection.
For the first issue, there are is a simple way of seeing what I'm talking about; If you are trying to optimize an algorithm for given results, there are three broad techniques which I will categorize for simplicity as 'stupid', 'random', and 'smart.'
For instance, if I wanted to sort a deck of cards, I could just shuffle it until I had a sorted deck. That's 'random.' This is not the worst you can do, and only if you do worse can random be an improvement. To do worse, you have to actively prevent the deck from becoming sorted. (For example, by using an algorithm that guarantees a 1-3-2 order at the start.) Randomness is not optimization, and stupidity is optimization away from the goal. Smart is convergence on a goal.
However, evolution is not a goal directed process. Those who exist are simply those who lived long enough in the environments they happened find themselves. Randomness doesn't improve any organism or any feature of any organism: it only improves diversity, which allows for more niches to be filled. I mean, maybe this increases the availability of food or the amount of space per organism or something, but it doesn't actually improve organisms. It improves the environment by making it less hostile to life in the abstract.
So it has nothing to do with hill climbing or optimization per se.
For the first issue, there are is a simple way of seeing what I'm talking about; If you are trying to optimize an algorithm for given results, there are three broad techniques which I will categorize for simplicity as 'stupid', 'random', and 'smart.'
For instance, if I wanted to sort a deck of cards, I could just shuffle it until I had a sorted deck. That's 'random.' This is not the worst you can do, and only if you do worse can random be an improvement. To do worse, you have to actively prevent the deck from becoming sorted. (For example, by using an algorithm that guarantees a 1-3-2 order at the start.) Randomness is not optimization, and stupidity is optimization away from the goal. Smart is convergence on a goal.
However, evolution is not a goal directed process. Those who exist are simply those who lived long enough in the environments they happened find themselves. Randomness doesn't improve any organism or any feature of any organism: it only improves diversity, which allows for more niches to be filled. I mean, maybe this increases the availability of food or the amount of space per organism or something, but it doesn't actually improve organisms. It improves the environment by making it less hostile to life in the abstract.
So it has nothing to do with hill climbing or optimization per se.
I think we're talking past each other. I'm not really sure what claim I made you're responding to. I was responding to this claim you made, with the context of "evolution":
> ...it is practically impossible to improve through random effects.
It's true that evolution is not aimed at a specific target. I made that point in my comment.
>Randomness doesn't improve any organism or any feature of any organism: it only improves diversity...
Here is a list of examples of beneficial mutations: http://www.gate.net/~rwms/EvoMutations.html It includes things like "adaption to high and low temperatures" and "12% (3 out of 26) random mutations in a strain of bacteria improved fitness in a particular environment."
The claim is that random mutations can occur -- at some rate, low though it may be -- and are more likely to be kept through natural selection.
> ...it is practically impossible to improve through random effects.
It's true that evolution is not aimed at a specific target. I made that point in my comment.
>Randomness doesn't improve any organism or any feature of any organism: it only improves diversity...
Here is a list of examples of beneficial mutations: http://www.gate.net/~rwms/EvoMutations.html It includes things like "adaption to high and low temperatures" and "12% (3 out of 26) random mutations in a strain of bacteria improved fitness in a particular environment."
The claim is that random mutations can occur -- at some rate, low though it may be -- and are more likely to be kept through natural selection.
You're probably right. Maybe I was just stretching to bring up a point that might be irrelevant.
It's really not all that impossible for singular mutations, hence evolution. Further, adaptations composed of independently maladaptive mutations can occur. This is the point of the comment you responded to. They are unlikely, but he alluded to that.
Article fails to mention: the eyes of the squid and octopus are very similar to ours in overall structure, but are not "wired backwards". So it seems that any explanation of why backwards is actually "vision-enhancing" is incomplete unless it also explains why it would not be enhancing for the squid. (though perhaps a justification could exist based on different wavelengths and lighting conditions underwater)
The vertebrate eye evolved under water as well (in fish).
Related: "Why we have blind spots - and how to see the blood vessels inside your own eye"
https://www.youtube.com/watch?v=L_W-IXqoxHA
https://www.youtube.com/watch?v=L_W-IXqoxHA
When I read this, I felt anxious about amount of time it takes to evolve eyes compared to my lifespan. Feeling so small.
I hope my cells don't evolve during my lifespan, because if they do it means I have cancer.
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Don't worry, the cancer will then evolve politicians, who will hail that evolution as an unprecedented innovation, claiming that only further innovation and economic growth will solve cancer's problems. They'll point out how cancer cells are special compared to other cells: how they've conquered the natural causes of death and overcome many logistical obstacles to build a complex high-density society with a rich history and lots of diversity.
Intrepid cells (no doubt sick of the crowding in their native tumor) will sometimes set out to explore and colonize the unruly wild parts of the body. It will be hard, but a few of those colonists will succeed in establishing far-flung outposts.
Surely there will be a few environmentalist cancer cells that oppose the "development" of the body, but the common perception among cancer cells will likely be that those cells are just standing in the way of progress, and anyway that the body is so vast that a single cancer cell can't do very much to effect the outcome.
/remove tongue from cheek ;)
Intrepid cells (no doubt sick of the crowding in their native tumor) will sometimes set out to explore and colonize the unruly wild parts of the body. It will be hard, but a few of those colonists will succeed in establishing far-flung outposts.
Surely there will be a few environmentalist cancer cells that oppose the "development" of the body, but the common perception among cancer cells will likely be that those cells are just standing in the way of progress, and anyway that the body is so vast that a single cancer cell can't do very much to effect the outcome.
/remove tongue from cheek ;)
That the retina has the receptive cells under the 'cabling' is not novel and is well studied. The authors here introduce the study of the glial 'supporter' cells and their refractive indices as wave guides for light to the receptive cells. This is actually pretty cool! Most neuroscience and physiology hasn't considered this as an advantage before, just a quirk of evolution that the eye is 'backwards'. Also, for other readers out there, the structure of the retina may be a good reference (https://en.wikipedia.org/wiki/Retina). To note: there are regions of the retina that differ in cone/rod concentration. The Fovea, the center of our vision, is entirely cones, while the outside is almost entirely rods. Also, the receptive cells have many synapses where data is processed before it going to the optic nerve. The retina acts similar to an FPGA in that the whole data set is compressed before transfer.
This has always been listed as a "proof" that God did not create people because why would he mess up this design?
Which isn't how this works, philosophically speaking.
The best argument for evolution isn't a listing of how badly-designed we are, it's a simple observation that the one simple principle of natural selection through modified descent suffices to explain us. We don't need any other hypothesis. Therefore, the principle of parsimony kicks in and other, more complicated, hypotheses are ruled out. Not absolutely, but fairly strongly, at least until we find things that our current hypothesis cannot explain, which hasn't happened yet.
The best argument for evolution isn't a listing of how badly-designed we are, it's a simple observation that the one simple principle of natural selection through modified descent suffices to explain us. We don't need any other hypothesis. Therefore, the principle of parsimony kicks in and other, more complicated, hypotheses are ruled out. Not absolutely, but fairly strongly, at least until we find things that our current hypothesis cannot explain, which hasn't happened yet.
The idea that, since a certain explanation appears to suffice, it must therefore be the truth, is an obvious fallacy.
Besides that, there are many people who disagree that it suffices to explain us.
Besides that, there are many people who disagree that it suffices to explain us.
Well, the GP was really just obliquely calling back to Occam's Razor. Evolution is a very simple process that explains biological complexity, compared to creationism, which requires a sentient creator to have invented the universe wholesale.
Of course, Occam's razor should be treated as a guide... it's no proof.
Of course, Occam's razor should be treated as a guide... it's no proof.
Truth? No. Just a best guess based on evidence. And the people who disagree are free to provide more evidence in favor of their contention.
That is a most excellent explanation.
More of a counter to the intelligent design argument. Well, at least to the intelligent part. Proponents of intelligent design tend to be religious, and having difficulty accepting a fallible deity
This is how I use it in debates where intelligent design proponents will on top of the complexity argument tend to use examples of how fantastic everything is as evidence of design. A blatant example of something that seems so in your face obviously flawed tends to throw them.
It's also useful because the complexity of the eye is often used as an argument for ID on the assumption that an incomplete eye would be useless, but for the eye we do have a long range of intermediate stages that would provide useful levels of sight, and we can show a long range of variations over eyes in existing organisms.
It's also useful because the complexity of the eye is often used as an argument for ID on the assumption that an incomplete eye would be useless, but for the eye we do have a long range of intermediate stages that would provide useful levels of sight, and we can show a long range of variations over eyes in existing organisms.
Also, thoughtful design pushes things toward simplicity, not complexity.
If the universe and everything in it--including ourselves--was created by an intelligent creator being, then we would be in no place to judge whether such a being was fallible. The very concept of what constitutes an error would be defined by the being itself.
With this premise, will not "intelligent" be as questionable as fallible?
Your question is so loaded it is bursting at the seams.
What qualifies as "messed up?" Having a design that appears suboptimal?
What would be not-messed-up, or what would be perfect? Having vision equivalent to a hawk? A telescope?
Why do you assume a creator being would necessarily choose to make perfect things? What if creating perfect things was not the creator's purpose? What if its creation was perfect for its intended purpose?
If a supernatural being exists and created the universe and us, it's ludicrous to think that we could put ourselves in its place and say, "Well, obviously he should have done it like this instead, therefore he doesn't exist."
We can't even understand how our own brain works, but some of us think that we are smarter than God. Regardless of what you believe about the existence of a supernatural creator, it's obvious that we would be inferior to such a being.
What qualifies as "messed up?" Having a design that appears suboptimal?
What would be not-messed-up, or what would be perfect? Having vision equivalent to a hawk? A telescope?
Why do you assume a creator being would necessarily choose to make perfect things? What if creating perfect things was not the creator's purpose? What if its creation was perfect for its intended purpose?
If a supernatural being exists and created the universe and us, it's ludicrous to think that we could put ourselves in its place and say, "Well, obviously he should have done it like this instead, therefore he doesn't exist."
We can't even understand how our own brain works, but some of us think that we are smarter than God. Regardless of what you believe about the existence of a supernatural creator, it's obvious that we would be inferior to such a being.
> We can't even understand how our own brain works, but some of us think that we are smarter than God.
If you refuse us the right to make any claims about a god, you also refuse the right to make any arguments for it.
Obviously, ars was talking about the gods mentioned in popular religious texts. These texts make very specific claims about what their gods are and do.
Arguing about arbitrary gods is, of course, largely fruitless. However, belief in them is equally fruitless.
If you refuse us the right to make any claims about a god, you also refuse the right to make any arguments for it.
Obviously, ars was talking about the gods mentioned in popular religious texts. These texts make very specific claims about what their gods are and do.
Arguing about arbitrary gods is, of course, largely fruitless. However, belief in them is equally fruitless.
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I actually really enjoy watching Dawkins' argument against intelligent design get shredded by basic modelling. Not that I believe in intelligent design, but because Dawkins is a smug bastard who wove an entire argument on a fallacious assumption.
Link?
I cant's see the argument shredded by modeling....
Sure. It's pretty straightforward. Dawkins is making an argument against intelligent design. He does so by setting up an artificial argument:
1) The eye is "backwards"; light has to pass through the wiring
2) any engineer dislikes disarray; why would they design a photoreceptor where the light has to pass through the wiring
3) therefore, it's unlikely that eyes were "designed", for if they were, they would be much nicer and more tidy.
(see The Blind Watchmaker, "This means that the light, instead of being granted an unrestricted passage to the photocells, has to pass through a forest of connecting wires, presumably suffering at least some attenuation and distortion (actually probably not much but, still, it is the principle of the thing that would offend any tidy-minded engineer)".
In short, Dawkins argument is weak- it appeals to design tidiness, not to any real facts or logic about how evolution works. But as this modelling (oh, and I see they did some experimental work as well) shows, it's just as likely that the mammalian eye configuration isn't as bad as he said.
The arguments against intelligent design should be based on reality. Dawkins is probably right about this sort of thing (that there is no ID), but he's typically right for the wrong reason (specious logic).
(Dawkins then further argues against parallel evolution, although we're now finding out it's also quite common. he's wrong about a lot of things).
I should further argue that finding the eye in this configuration "backwards" according to some, is really just applying human aesthetics about how things should be engineered, where biology is a combination of happenstance and optimization. I suspect, as we tease out the biophysics of the eye further, we will find many more examples of how Dawkins' simple logic (which isn't really logic, but more based on aesthetics and intuition) doesn't really explain things.
(see The Blind Watchmaker, "This means that the light, instead of being granted an unrestricted passage to the photocells, has to pass through a forest of connecting wires, presumably suffering at least some attenuation and distortion (actually probably not much but, still, it is the principle of the thing that would offend any tidy-minded engineer)".
In short, Dawkins argument is weak- it appeals to design tidiness, not to any real facts or logic about how evolution works. But as this modelling (oh, and I see they did some experimental work as well) shows, it's just as likely that the mammalian eye configuration isn't as bad as he said.
The arguments against intelligent design should be based on reality. Dawkins is probably right about this sort of thing (that there is no ID), but he's typically right for the wrong reason (specious logic).
(Dawkins then further argues against parallel evolution, although we're now finding out it's also quite common. he's wrong about a lot of things).
I should further argue that finding the eye in this configuration "backwards" according to some, is really just applying human aesthetics about how things should be engineered, where biology is a combination of happenstance and optimization. I suspect, as we tease out the biophysics of the eye further, we will find many more examples of how Dawkins' simple logic (which isn't really logic, but more based on aesthetics and intuition) doesn't really explain things.
From the article, "..we also noticed something rather curious: the colours that best passed through the glial cells were green to red, which the eye needs most for daytime vision. The eye usually receives too much blue – and thus has fewer blue-sensitive cones."
From another article on the same site, https://theconversation.com/a-dark-night-is-good-for-your-he...
"Light from the Sun is strong in blue, short wavelength light ..when it comes in the evening or during the night, it fools the body into thinking it’s daytime. We now know that this bright blue light has the strongest effect on lowering melatonin during the night. Your tablet, phone, computer or compact fluorescent lamp (CFL) all emit this kind of blue light."
From another article on the same site, https://theconversation.com/a-dark-night-is-good-for-your-he...
"Light from the Sun is strong in blue, short wavelength light ..when it comes in the evening or during the night, it fools the body into thinking it’s daytime. We now know that this bright blue light has the strongest effect on lowering melatonin during the night. Your tablet, phone, computer or compact fluorescent lamp (CFL) all emit this kind of blue light."
That's why I take melatonin tablets ~20min before bed. It's one of the best known methods to improve your sleep and overall well being.
http://www.gwern.net/Melatonin
http://www.gwern.net/Melatonin
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The human eye has always made me wonder of the sheer complexity of the human body. It's an amazing epitome of evolutionary success...
Epitome? Nah. The human body is flawed in any number of ways. This article has some interesting notable examples:
http://www.smithsonianmag.com/science-nature/the-top-ten-dai...
Humans are optimized in some very specific ways, but at the expense of some serious downsides.
As a related aside, I think its this misunderstanding that confuses people into preferring creationism. If one holds the anthropocentric view that humans are the peak of biological evolution (itself a meaningless concept... Evolution is about fitness, it's not directional), believing in creationism is a lot more understandable.
http://www.smithsonianmag.com/science-nature/the-top-ten-dai...
Humans are optimized in some very specific ways, but at the expense of some serious downsides.
As a related aside, I think its this misunderstanding that confuses people into preferring creationism. If one holds the anthropocentric view that humans are the peak of biological evolution (itself a meaningless concept... Evolution is about fitness, it's not directional), believing in creationism is a lot more understandable.
> The human body is flawed in any number of ways.
Yes; “This project is doomed.”:
http://threepanelsoul.com/2010/07/05/on-design-by-committee/
Yes; “This project is doomed.”:
http://threepanelsoul.com/2010/07/05/on-design-by-committee/
From the article:
> One of the reasons it is so difficult to stop hiccupping is that the entire process is controlled by a part of our brain that evolved long before consciousness, and so try as you might, you cannot think hiccups away.
I can. Reliably. I concentrate in the general direction of my diaphragm, and often times I can stop the third hiccup before it happens. I have to wait until the second hiccup before I know I'll have to use the technique. The only time I can't do it is when I've been drinking, which is, coincidentally, when I get them the most. I can't concentrate the way I need to, it's like that part of my brain is shut off.
> One of the reasons it is so difficult to stop hiccupping is that the entire process is controlled by a part of our brain that evolved long before consciousness, and so try as you might, you cannot think hiccups away.
I can. Reliably. I concentrate in the general direction of my diaphragm, and often times I can stop the third hiccup before it happens. I have to wait until the second hiccup before I know I'll have to use the technique. The only time I can't do it is when I've been drinking, which is, coincidentally, when I get them the most. I can't concentrate the way I need to, it's like that part of my brain is shut off.
For fun, maybe try to "count" with the stops. 3rd hiccup, 4th hiccup, 5th hiccup.
That would be a much more compelling anecdote about control.
That would be a much more compelling anecdote about control.
When I'm drunk enough to not be able to stop my hiccups, they usually go away naturally without me even noticing them as I sober up. I eventually give up trying to control it after I notice it's futile, and the awareness that I'm even having them goes away. The hiccups themselves barely register and are quickly forgotten.
A couple of times I've gotten home realization dawns that I'm still hiccuping. Two, three hiccups later, they're gone. There's something about being alone in my room that makes me more capable of doing the technique than when I'm at the bar.
A couple of times I've gotten home realization dawns that I'm still hiccuping. Two, three hiccups later, they're gone. There's something about being alone in my room that makes me more capable of doing the technique than when I'm at the bar.
>It's an amazing epitome of evolutionary success...
And so is every other species. We've all been evolving together on this planet for the same amount of time.
This is why driving species to extinction is so spectacularly stupid — it squanders our collective legacy of genetic information, hard-won over billions of years of struggle. How many discoveries like this will never be made because we destroyed the species? Worse, how many useful functional species are we depriving ourselves of (including functions we don't even know we need yet)?
And so is every other species. We've all been evolving together on this planet for the same amount of time.
This is why driving species to extinction is so spectacularly stupid — it squanders our collective legacy of genetic information, hard-won over billions of years of struggle. How many discoveries like this will never be made because we destroyed the species? Worse, how many useful functional species are we depriving ourselves of (including functions we don't even know we need yet)?
I've been making the argument that we should be sequencing the DNA of endangered species. Preserve some of that legacy digitally before it's too late.
Very cool! I've often wondered about that.
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Also, the author's ignorance of biology concerns me. In one comment, he thought that color-blind people saw in grayscale. If you know how human cone and rod cells are set up, such an idea seems preposterous.